No.1 Sleep Expert: Magnesium Isn’t Helping You Sleep! This Sleep Habit Increases Heart Disease 57%

No.1 Sleep Expert DR. MATTHEW WALKER reveals how to fix insomnia, reset your circadian rhythm, deepen REM sleep, and why magnesium and melatonin may be hurting your sleep. Dr Matthew Walker is a Professor of Neuroscience and Psychology at the University of California, Berkeley, and one of the world’s leading experts on sleep science, with over 20 years of research. He is host of The Matt Walker Podcast and bestselling author of ‘Why We Sleep: The New Science of Sleep and Dreams’. He explains: ◼️The shocking link between poor sleep timing and increased cancer risk ◼️How alcohol and caffeine silently sabotage deep sleep and mental performance ◼️Why screen time and light exposure before bed are secretly rewiring your brain ◼️How “sleep banking” before stress, travel, or work sprints can boost resilience ◼️Why parents, professionals, and athletes all need radically different sleep strategies Enjoyed the episode? Share it using this link and get points for every referral: https://doac-perks.com (00:00) Intro (02:33) Sleep Changes Your DNA (05:01) The Stigma Around Sleep and Laziness (08:43) What’s Stopping People From Sleeping? (10:58) The Shocking Link Between Weekend Sleep-Ins and Heart Disease (14:48) New Research: Sleep Banking for Low-Sleep Periods (16:25) Boost Cognitive Performance With This Sleep Hack (19:14) 3 Things That Will Improve Your Sleep Quality Tonight (20:42) It’s Not Blue Light That’s Keeping You Awake (22:01) Melatonin Doesn’t Make You Sleep — Here’s What It Does (24:28) The Right Amount of Melatonin (25:55) The 1% With Nocturnal Clocks Who Can’t Sleep Until 3 AM (27:26) Should You Be Concerned About Melatonin as a Sleep Aid? (30:33) The Trade-Offs in Sleep Medicine (35:05) The Key to a Digital Detox (35:46) The 4 Macros of Good Sleep: QQRT (37:02) The Minimum Amount of Sleep You Need to Stay Alive (42:49) How Sleep Regularity Predicts Life Expectancy (46:50) Try This 7-Day Sleep Enhancer Challenge (53:24) Is Your Room Dark Enough for Optimal Sleep? (1:01:03) Why Counting Sheep Doesn’t Work (1:02:58) A Better Alternative to Counting Sheep (1:04:36) Does Magnesium Really Help With Sleep? (1:11:47) Ads (1:13:33) How REM Sleep Works and How to Maximize It (1:20:30) Why REM Sleep Is So Important (1:22:07) Entering a ‘Psychotic’ State During Dreams (1:25:05) Healing Trauma Through Dreams (1:31:12) Nightmares as a Warning Sign of Mental Health Issues (1:36:09) REM Sleep Is Like Group Therapy for Memories (1:39:31) Ads (1:41:18) The Dystopian Future: Superhumans Who Sleep Only 6 Hours (1:45:17) Could Humans Be Engineered to Sleep Less? (1:50:20) Why Undersleeping Triggers Cravings (1:54:36) A New Drug That Could Help With Insomnia (2:03:50) What Did Success Bring You? (2:07:33) I Didn’t Believe in Finding “The One” (2:28:39) The Future of AI and Sleep Follow Dr Matthew: X - https://bit.ly/4oIRpAY Instagram - https://bit.ly/49OgFB4 Podcast - https://bit.ly/489MJhA You can purchase Dr Matthew’s book, ‘Why We Sleep’, here: https://amzn.to/3K04IxJ The Diary Of A CEO: ◼️Join DOAC circle here - https://doaccircle.com/ ◼️Buy The Diary Of A CEO book here - https://smarturl.it/DOACbook ◼️The 1% Diary is back - limited time only: https://bit.ly/3YFbJbt ◼️The Diary Of A CEO Conversation Cards (Second Edition): https://g2ul0.app.link/f31dsUttKKb ◼️Get email updates - https://bit.ly/diary-of-a-ceo-yt ◼️Follow Steven - https://g2ul0.app.link/gnGqL4IsKKb Sponsors: Linkedin Ads - https://www.linkedin.com/DIARY Pipedrive - http://pipedrive.com/CEO KetoneIQ - Visit https://ketone.com/STEVEN for 30% off your subscription order Last chance to join the waitlist for the limited edition Diary Of A CEO Conversation Cards here: https://bit.ly/cardswaitlist

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:00Dr. Matthew Walker?

  Here's the problem with magnesium supplementation when it comes to sleep. The first thing to note is that most forms of magnesium don't cross the brain barrier, and sleep is produced by your brain. So how can something that doesn't get into your brain affect the brain process? All you're doing is creating probably expensive urine.

• 0:18Dr. Matthew Walker?

  However, there is one form of magnesium that seems to have some evidence in favor of it, which we can speak about, but it doesn't stop there. There's so much new evidence that we have, including this myth of eight hours. My fear about giving melatonin to kids, why you keep them waking up in the middle of the night, and the invention of the first new class of sleeping medication that I actually favor, and most people are not aware of it.

• 0:41Steven Bartlett?

  Okay, let me write this down. Matthew Walker is back, and the world-renowned sleep expert and neuroscience professor

• 0:47Speaker 02

  is sharing brand-new research to combat the sleep loss epidemic and help you get the perfect night's sleep.

• 0:53Dr. Matthew Walker?

  As a society, we have struggles with sleep at night due to many reasons, but no one teaches us this stuff. And it's things like, say, you go to bed at 11 one night, 1 a.m. the next night, then 10:30 p.m. the next night, and it's remarkable how many people do this. But studies have shown that you are statistically 49% more likely to prematurely die versus those people who are most regular in terms of going to bed and waking up at the same time. And worse, they had a 57% cardiometabolic disease risk increase. What the? Science really teaches us that there are four pillars of good sleep. And then there's this incredible new study looking at sleep banking. And this is remarkable for people who are facing a sprint at work or a medical doctor about to go on call for the next 40 hours, new parent, and we can go through all of that.

• 1:37Dr. Matthew Walker?

  But if you were to push me to say the three most impactful things that you can start doing tonight to start sleeping better, it would be...

• 1:49Steven Bartlett?

  Just give me 30 seconds of your time. Two things I wanted to say. The first thing is a huge thank you for listening and tuning into the show week after week. It means the world to all of us, and this really is a dream that we absolutely never had and couldn't have imagined getting to this place. But secondly, it's a dream where we feel like we're only just getting started. And if you enjoy what we do here, please join the 24% of people that listen to this podcast regularly and follow us on this app. Here's a promise I'm going to make to you. I'm going to do everything in my power to make this show as good as I can now and into the future. We're going to deliver the guest that you want me to speak to, and we're going to continue to keep doing all of the things you love about the show. Thank you.

• 2:33Steven Bartlett?

  Dr. Matthew Walker. Here in front of me, I have these cards, which I'm going to reveal a bit later. But these kind of hold what you consider to be the four pillars of great sleep. But you also spend much of your professional career just studying the brain generally to understand human performance and how we can change our lifestyles and also introduce some of these new sort of treatments to improve how our brain performs. And I want to talk about all of that as well. But to start, for anyone that is unfamiliar with you and has been hiding under a rock. How do you summarize who you are professionally, the sort of academic references you're drawing on, and the experiences and research you've done so that the viewer listening at home

• 3:16Steven Bartlett?

  understands the full world that you operate in, study and have experienced?

• 3:21Dr. Matthew Walker?

  I am a neuroscientist by trade, but my speciality is sleep, the effects of sleep on the brain and the body. And I've probably spent about the past two decades trying to understand exactly why do we sleep? Because 50 years ago, the crass answer to the question, why do you sleep? Was the following: you sleep to cure sleepiness, which is the factious equivalent of saying, well, you eat to cure hunger. No, you don't eat to cure hunger. You eat to support all sorts of physiological and biological benefits. But now, and this is not due to my research, it's to all of the incredible colleagues whose sort of shoulders that I stand on, we've now had to upend the question.

• 4:05Dr. Matthew Walker?

  We now have to ask, is there any major physiological system in your body? Or is there any operation of your mind that isn't wonderfully enhanced by sleep when you get it or demonstrably impaired when you don't get enough? And the answer now seems to be, no, there is no such system, even down to the level of your DNA. Your sleep and how you are sleeping or not sleeping will change the very DNA nucleic alphabet that spells out your daily health narrative. And we can see it all the way up to society. Sleep can change the fabric of society, can change how we interact with other people, it can change our belief systems, it can change how lonely

• 4:48Dr. Matthew Walker?

  or sort of hyper-social we are. So to your question, I'm a sleep scientist by trade and I suppose my mission has been trying to reunite humanity with the sleep that it seems to be so bereft of.

• 5:01Steven Bartlett?

  We had a fantastic conversation last time and my audience valued it tremendously. I know that because we often survey our audience and we get to see some of the backend stats. And this conversation about sleep is particularly personal to everybody listening because when we surveyed our audience ahead of this conversation today, about seventy-five or eighty percent of the Dara Vaseo audience struggle with sleep for a variety of different reasons. So we actually asked them, a thousand of them, their questions to ask you today. But also, the other reason I really wanted to chat to you is the science of sleep, I mean, as is the way of science, is always evolving. We're learning new things. And even since we spoke last time, there is new sleep science, which we're going to talk about today. And one of those particular things we're going to talk about is going to be demonstrated using this jar.

• 5:46Steven Bartlett?

  Because I always want to know what the updated sleep science is so that I can be a better sleeper. Because I agree with everything you've said about how foundational sleep is in my life. And I didn't know this at the start of my career. I didn't know this even a couple of years ago, five years ago. I didn't know, I thought sleep was one of those things you could just take it all or leave.

• 6:07Dr. Matthew Walker?

  Yeah, I mean, and it's not your fault in so many ways. Because if you didn't know what I know, you would just think, well, when I sleep, my body is dormant and my mind, for the most part, is blank. So is it so catastrophic to lose, you know, an hour or two of sleep? And, you know, you have to then think about, from an evolutionary perspective, it is such an idiotic idea to sleep. Because when you're sleeping, you're not finding a mate, you're not reproducing, you're not caring for your young, you're not foraging for food. And worse of all, you're vulnerable to predation. So on any one of those grounds, and especially all of them as a collective, sleep should have been strongly selected against in the course of evolution.

• 6:51Dr. Matthew Walker?

  And my point is that, and it's often been said that if sleep doesn't serve an absolutely vital set of functions, plural, then it's the biggest mistake the evolutionary process has ever made. And we now realise it didn't make a spectacular blunder. But really, I guess, the point of it is, sleep is not a passive state. It's an incredibly active state, both in the terms of the brain and the body. And so you should not feel sort of, you know, remiss or ashamed that you didn't value the importance of sleep, because firstly, as a subjective sense, you just think, well, my mind was offline for a while. Second, we also know that we don't teach the importance of sleep in education. And doctors themselves, you know, there's a great study, and what they found was

• 7:34Dr. Matthew Walker?

  that medical doctors across, I think it was about 11 different curricula around the world, they will only receive about 1.2 hours of education on sleep. But it's a third of their patients' lives. So there's a collection of sort of almost perfect storms that have happened to keep society ignorant of the importance and the value of sleep. I think that's why we often so shortchange it, together with also something terrible, which is stigma. That people are so proud to say, well, I've been eating really healthy the past couple of months, or, you know, I've been going to the gym, you know, three times a week consistently for the past year.

• 8:19Dr. Matthew Walker?

  No one is ever going out into society and saying, you know, I've been getting eight and a half hours of sleep consistently every night. Because if you did, people would say, really? And there's a, there's a slight edge to the really, which is that if you have time to sleep, then you must not be busy. And if you're not busy, you must not be important.

• 8:43Steven Bartlett?

  So can you do me a favor? And for the listener at home, can you tell me what the different groups of people that are listening to this conversation right now are seeking? From the extreme end being sleep apnea, I get no sleep, I'm an insomniac, to the other end where maybe they're looking for marginal performance gains. Like, what are the cohorts of people you see and the reasons why they're so interested in your work? They listen to your podcast, they read your books. What are the cohorts?

• 9:10Dr. Matthew Walker?

  Firstly, we have the collection of people who have insomnia, those people who have other sleep disorders like sleep apnea, which we can speak about. There's another disorder called restless leg syndrome. It's a terrible disorder where your legs start to feel as though they've got this sort of creepy crawly feeling and you've constantly got to massage them and move them. It's a terrible disruptor of your sleep. All of these disorders are markedly undiagnosed, by the way. And then you've got another collection of individuals who they don't have any sleep disorders, but they are either doing things that will dismantle their sleep. So either they're taking on things into themselves, like alcohol, caffeine, THC,

• 9:51Dr. Matthew Walker?

  that aren't their sleep helpers, even though sometimes they think they are. And then you've got perhaps the internal things that will prevent you from sleeping well, things like stress and anxiety. And then you've also just got life itself that can get in the way. And then moving from the sleep disorders realm to the "I don't have a sleep disorder, but I'm probably not doing it right," quote unquote, when it comes to sleep. Then you've got the people who are obsessed about getting it right. And they are the bio optimizers, this sort of the bio hackers. And then you've also got, I work with a lot of high performance individuals who are

• 10:33Dr. Matthew Walker?

  really trying to just scratch out those last couple of percentages. Either it's in business or often we're working with professional athletes. These are the people for whom two or three percentage point changes can be Tens of millions of dollars, or they can be the difference between standing on a podium at the Olympics or not. And so this is a broad collection of wonderful characters.

• 10:58Steven Bartlett?

  And since we last spoke, is there now a lot of new sleep science and understanding as it relates to sleep performance and these three categories of sleep deficient sleep disorders, lifestyle factors, and then the optimizers?

• 11:11Dr. Matthew Walker?

  Yeah, I think there's this broad collection of new evidence that we have. But maybe let me come on to the middle group. You know, I used to say that for people who were deficient in their sleep, that sleep wasn't like the bank, that you can't accumulate debt. Oh, here we go. Okay. So what we can see here is that the jar used to be full, full of sleep credit when you're sleeping well. And then during the week, I'm short sleeping, so maybe I'm only getting five hours a night. So I'm constantly going into debt. So I'm losing all of this wonderful sleep credit, and my system is building up this collateral debt.

• 11:53Dr. Matthew Walker?

  And then we used to think that sleep was not like the bank, that once you've gone into debt, unfortunately,

• 12:02Dr. Matthew Walker?

  the lid is closed. And even at the weekend, if you try to pay it back, you can't put back credit into the system. However, there was a study published from what's called the UK Biobank, which is this incredible data set. It's revolutionary. And they studied in this particular research paper, over 90,000 individuals. And what they did was they essentially split them down into those individuals who were short sleeping during the week and then short sleeping at the weekend. And they compared them to those individuals who were short sleeping during the week. But then Long sleeping at the weekend, they were doing catch-up sleep.

• 12:41Steven Bartlett?

  That's me.

• 12:42Dr. Matthew Walker?

  And that's so many individuals.

• 12:44Steven Bartlett?

  Yeah.

• 12:44Dr. Matthew Walker?

  It turns out, if you look at the data, it's remarkable how many people do this, this catch-up sleep behavior. But what was amazing is that in the people who were short sleeping during the week, but long sleeping at the weekend, they had a 20% reduced cardiovascular disease risk relative to the people who were short sleeping during the week, but also short sleeping at the weekend. Now, to be clear, both of those groups had a higher cardiovascular disease risk than people who were sleeping sufficiently during the week and sleeping sufficiently during the weekend. So I'm not saying that it's a completely free lunch. But for the first time, we realized that at least one system, major organ system in

• 13:26Dr. Matthew Walker?

  your body, is like the bank, which is that if your heart at the weekend,

• 13:36Dr. Matthew Walker?

  you can just keep putting credit back and your system doesn't suffer as much.

• 13:44Steven Bartlett?

  For your heart?

• 13:45Dr. Matthew Walker?

  For your heart.

• 13:45Steven Bartlett?

  Okay.

• 13:46Dr. Matthew Walker?

  But again, many of the other major physiological systems don't show that. So work by people like Kenneth Wright at the University of Boulder, Colorado, he's shown that your immune system doesn't rebound after long sleep at the weekend, your regulation of blood sugar, your cognitive ability. So that's one way in which I've changed my mind regarding sleep and the bank. But there's a very different new set of data that has changed my mind completely about this idea of sleep and the bank. Now, what we've just discussed here is to say, I went into debt and then I was hoping to try and pay it off with credit at the weekend.

• 14:24Steven Bartlett?

  So the jar represents the debt that you have, the sleep debt?

• 14:27Dr. Matthew Walker?

  Correct.

• 14:27Steven Bartlett?

  Yeah.

• 14:27Dr. Matthew Walker?

  And what I'm trying to do is force more coinage.

• 14:34Dr. Matthew Walker?

  In at the weekend to see if I can offset the debt that I created and get back to net, net neutral by the end of the weekend. Now, it turns out you can't do that, even if you sleep for as long as you want. But here's this new remarkable data. It came from Walter Reed Medical Army Institute, a researcher called Thomas Balkin. And what he was interested in was flipping the direction of the question. Not if I go into debt, can I pay back with credit? But what if I know in future I'm going to face a debt, an upcoming debt? Can I do sleep banking?

• 15:13Steven Bartlett?

  Oh, so if I've got a big thing coming up where I'm traveling across the world and I know I'm going to be sleep deficient, can I sleep a lot before it to create a? What would the financial analogy be?

• 15:24Dr. Matthew Walker?

  The financial analogy would be, let's say that we're coming up to Christmas.

• 15:28Steven Bartlett?

  Yeah.

• 15:29Dr. Matthew Walker?

  And you're going to spend lots on, you know, presents and all sorts of stuff. So I know that in October and November, I'm going to tighten my financial belt.

• 15:38Steven Bartlett?

  I see.

• 15:39Dr. Matthew Walker?

  So that when I go into the sort of Christmas period and I'm spending a lot more money, my bank account isn't hit as hard. I don't go into as much of a sort of a debt situation because I've built up credit.

• 15:52Steven Bartlett?

  So you can create sleep savings?

• 15:54Dr. Matthew Walker?

  Correct. It's a sleep saving system. So essentially, what he was able to do, not just put the jar to full, but he was actually packing in even more. So that you almost got this wonderful overflow of sleep.

• 16:19Steven Bartlett?

  How did he know?

• 16:21Dr. Matthew Walker?

  He didn't. It was the experimental hypothesis.

• 16:23Steven Bartlett?

  And but how did they prove it?

• 16:25Dr. Matthew Walker?

  So what they did is that they woke you up to a period when you're going to have two or three nights of either no sleep or marked sleep reduction. And in the week beforehand, with these army cadets, instead of being limited to eight hours of time in bed, they were able to get 10 hours of time in bed and they could sleep all that they want. And so they went from probably an average of about seven, seven and a half hours of sleep to about eight and a half, almost nine hours of sleep. So they were extending their sleep duration.

• 17:00Dr. Matthew Walker?

  And so that they had built up this buffer. It's almost like a sort of a sleep safety net that's in place. So that when you go into the tumble of sleep deprivation, you're sort of almost bolstered and you're lifted higher. And therefore, your degree of impairment that you suffer under conditions of sleep deprivation is significantly less if you banked sleep beforehand versus those people who were just sleeping normally and then faced the deprivation. They went down much further in terms of their cognitive and mental performance.

• 17:34Steven Bartlett?

  So he gave them challenges and tasks to do.

• 17:37Dr. Matthew Walker?

  Correct.

• 17:37Steven Bartlett?

  In two different groups. One group had sleep savings saved up from sleeping well the previous week. One group didn't.

• 17:42Dr. Matthew Walker?

  That's right.

• 17:43Steven Bartlett?

  And they performed remarkably different.

• 17:45Dr. Matthew Walker?

  So both of them were impaired relative to a sleep rested person. However, the people, it's sort of, you know, how, how much of a drop in your cognitive performance do you suffer? And what he found was that people who had built up this credit, this savings account of sleep in the days in the week beforehand, they suffered about forty percent less of an impairment relative to the people who had not created any savings plan. Now, they weren't in debt. They were just net neutral. But boy, did they drop quickly. Whereas those people who'd had some cash in the sleep credit system, they didn't fall anywhere near as far.

• 18:28Dr. Matthew Walker?

  But this is remarkable for people, like you were saying, who are facing, let's say, if I've got a sprint at work or I'm a medical doctor, I know I'm about to go on call for the next forty hours. You're a military, aviation, all of the new parents, all of these circumstances are places where now we know. Athletes is a great example. When we work with athletes, people like Michael Grandner have demonstrated that athletes sleep terribly typically the night before a huge performance. No matter, you know, of course, the nerves. But what you can do is you can have them bank sleep in the days before when they're not as nervous. And therefore, their performance doesn't suffer as much, even though they know they're going to be deprived.

• 19:09Steven Bartlett?

  Sleep is so important, isn't it? And I think everybody now knows that because of people like yourself. Well, really, you know, you are the real pioneer in pushing this subject into the world. I remember when you first went on Joe Rogan's show, the amount of my friends that sent me that episode and then sent me your book was just staggering. It was like, that was the catalyst moment, I think, in society for the mainstream to really start talking and caring about sleep. However, there's still so many people struggling because of all the factors that you talked about. When we're talking about group two, who have those lifestyle factors, the stress, the psychological factors, the trauma, et cetera, et cetera. What can we give them, those people, the people that really, really struggle? Maybe they haven't got a disorder. We'll come to the people with sort of sleep disorders later and we'll talk about optimizers.

• 19:52Steven Bartlett?

  But what, what is the new information or advice that we can give them? That will help them once and for all, sleep eight hours a night and get their life back.

• 20:04Dr. Matthew Walker?

  If you were to push me to say, what are the three most impactful things that you can start doing tonight to start sleeping better? It would be the following. Digital detox.

• 20:18Steven Bartlett?

  Okay, let me write this down. Digital detox. Okay. And what does that mean?

• 20:22Dr. Matthew Walker?

  One hour before bed. Try to limit activating social media engagement, email and text messages that are going to trigger you. It's fine to listen to a podcast, you know.

• 20:38Steven Bartlett?

  Thank God for that.

• 20:40Dr. Matthew Walker?

  You heard it here, folks. Right from that one.

• 20:42Steven Bartlett?

  But it's also good to like and subscribe, would you say?

• 20:45Dr. Matthew Walker?

  I would say that, you know, like and subscribe and then just click here so that you get the latest notification. You get that bell. Just click on the bell icon so that you.

• 20:55Dr. Matthew Walker?

  So it's not a problem of blue light. A quick aside, we've been taught this myth of the blue light effect.

• 21:03Steven Bartlett?

  Yeah.

• 21:04Dr. Matthew Walker?

  From devices. And it really is a myth because an incredible Australian researcher, a guy called Michael Gradisar, has almost single-handedly changed the, the, what I think of as being the zeitgeist for a while. After a very influential paper, which is a great paper. And what they showed was that one hour of iPad reading before bed ended up impairing your melatonin. It disrupted sleep. It reduced the amount of dream sleep. And even after they stopped reading the iPad, the blast radius impact on your dream sleep lasted a week. It's almost like the drug needed to get washed out the system. That even when you'd stopped using technology for an hour before bed, the impact of that technology, even though you'd stopped using it,

• 21:46Dr. Matthew Walker?

  could still be seen in the echo of sleep disruption for a week later. It was a very influential city and a very prestigious channel.

• 21:53Steven Bartlett?

  When was that, a while ago?

• 21:54Dr. Matthew Walker?

  That was probably about 10 years ago. But then Michael Gradzard, this incredible Australian researcher, started to say, well, I can't replicate these findings. And what he was discovering is that it's not the blue light. That's the problem. Now, the blue light will change aspects of your melatonin. And melatonin is a hormone. It simply tells your brain and your body when it's nighttime, when it's time to fall asleep. It doesn't participate in the generation of sleep. Melatonin is like the starting official at the 100 meter race. It brings all of the racers to the line, and it begins the timing of the race. But it doesn't participate in the creation of the race itself. That's a different set of chemicals.

• 22:29Steven Bartlett?

  It doesn't make you go to sleep?

• 22:31Dr. Matthew Walker?

  It doesn't make you. And if you look at what we call meta-analyses, where we gather together all of the individual studies on a topic, and we put them in a big statistical bucket. What they found is that melatonin will only improve the speed with which you fall asleep by about 3.4 minutes. And it will only increase the efficiency of your sleep by about 2.2%. So not much more than placebo. So melatonin is... Now, the placebo effect is the most reliable effect in all of pharmacology. So, you know, maybe no harm, no foul. I would say, and don't forget, I will come back to the three, but when it comes to melatonin, be careful. More isn't always better.

• 23:13Dr. Matthew Walker?

  And you run the risk of confusing your morning brain into a dense nighttime fog. And what I mean by that is... Ten milligrams or twenty milligrams of melatonin is what we call a supraphysiological dose, which again is just a fancy medical term to say it's a size of magnitude of melatonin that your body would never naturally release. It's far greater. So melatonin is the signal of darkness and normally by the morning hours, our natural release of melatonin has stopped and you're down to zero levels again.

• 23:48Steven Bartlett?

  In the morning.

• 23:49Dr. Matthew Walker?

  In the morning. So you wake up and your body no longer has the signal of melatonin saying it's night, it's night, it's night. But if you've dosed yourself with ten milligrams or twenty milligrams of melatonin, you run the risk of saying, well, yes, I know it, quote unquote, knocks me out. But the problem is, in the first, you know, three or four hours of the waking morning, you're struggling because you're in this fog of a hormonal melatonin, a hormonal signal saying it's still pitch black. Now, it's not, it's bright light outside, but your body is fooled into thinking it's pitch black because you've dosed yourself too high and no wonder you're reaching for two or three cups of coffee in the morning.

• 24:27Steven Bartlett?

  So what dose of melatonin should I be taking?

• 24:30Dr. Matthew Walker?

  Somewhere between probably about point one to three milligrams.

• 24:36Steven Bartlett?

  And do you advise melatonin for people?

• 24:38Dr. Matthew Walker?

  Yes, in two conditions. The first, or circumstances, I should say, the first is when you're going through jet lag. Wonderfully helpful, but timing is critical. You need to create that sort of, that artificial signal of night because, let's say that you and I here in Los Angeles, we're both going to fly back to London tomorrow and London is eight hours ahead. So we fly overnight, we arrive in London and then that first night, let's say we decide to go to bed, or I decide to go to bed in the hotel at midnight. The problem is, here in Los Angeles, and my body clock, it's still four P M because London's eight hours ahead. So my melatonin is not going to rise for probably another six or seven hours.

• 25:23Dr. Matthew Walker?

  So I need to artificially hijack my melatonin system and tell my brain, oh no, it's not four P M. It's instead, it's midnight. And so they're, under conditions of jet lag, very helpful. The second is, if you have a circadian rhythm disorder, let's say that you're someone who has a, an advanced circadian phase. What that means is, you're someone who really can't get sleepy until three or four in the morning, and you would prefer to be sleeping throughout most of the day. So you, you're almost nocturnal.

• 25:55Steven Bartlett?

  Is that a genetic disorder?

• 25:56Dr. Matthew Walker?

  And yes, it's a genetic disorder in part.

• 25:58Steven Bartlett?

  How many people have that?

• 26:00Dr. Matthew Walker?

  Probably one to two percent of the population have a very severe, what we call an advanced circadian phase disorder. But their melatonin can also be helpful, because once again, their melatonin, part of their problem is that their melatonin is very delayed. So they don't get the signal of, oh, it's night, until maybe four o'clock in the morning. You and I, we start to get our signal of melatonin, depending on our chronotype, by somewhere between about nine, 10 or 11 P M. They may be delayed by five hours. So if we can give them melatonin, we can artificially try to fool their brain into thinking it's actually earlier in their biological rhythm. So they sleep earlier, and they're more in sync with the rest of society.

• 26:42Steven Bartlett?

  How does someone know if they're that type of person, if they have that disorder? Is there, there's not a way to test, is there?

• 26:47Dr. Matthew Walker?

  Well, what we typically do is, we will bring you into a laboratory, and we will measure your innate level. So we will shut out, sort of, all windows, all clock faces are gone, and we just let you run your natural rhythm.

• 26:59Steven Bartlett?

  Hmm.

• 27:00Dr. Matthew Walker?

  And they have the same rise and fall in melatonin, just like you and I do, except where it's doing that rise and fall of melatonin on the 24 hour clock face is radically different.

• 27:11Steven Bartlett?

  Okay.

• 27:12Dr. Matthew Walker?

  For you and I, it's, you know, nine, 10 P M, 11 P M at night, when we're starting that melatonin crescendo. For them, it's four o'clock in the morning. So we can measure it. It's not in their minds, it's not their choice, it's a biological edict.

• 27:26Steven Bartlett?

  Are you concerned that melatonin is becoming more and more popular as a way to solve lifestyle issues?

• 27:34Steven Bartlett?

  That have caused sleep impairment. Because I'm seeing loads of, you know, I'm an investor. So I see lots of companies now pitching me different products that have melatonin in them as a sort of day to day sleeping supplement.

• 27:47Dr. Matthew Walker?

  I think I'm really torn. I've been on both sides of this argument and I'm cautious about it for two reasons. The first is in pediatric populations here in the United States.

• 27:58Steven Bartlett?

  Pediatric?

• 27:59Dr. Matthew Walker?

  Yeah.

• 27:59Steven Bartlett?

  What does that mean?

• 28:00Dr. Matthew Walker?

  So the people's use of melatonin in kids is increasing. So in pediatric populations, it's increasing exponentially. And in fact, if you go down the sort of the supermarket aisles here in America, often if you go into sort of the the health sort of food section, there's this big purple section, that's the melatonin section. And a large proportion of that is there dedicated to gummies for your children with melatonin. And there was a study that was published about three years ago that showed here in America, over the past 10 years, there has been a 503% increase in poisonous overdose admissions to hospitals of melatonin in the past 10 years.

• 28:45Dr. Matthew Walker?

  503% increase. So firstly, we've got to be a bit careful. The second reason is that melatonin is a bioactive hormone and it's also involved in reproductive development. And there were studies done back in the 1970s, I think, where they were looking at juvenile male rats, which is to say male rats who were going through adolescence. And they were dosing them with high amounts of melatonin. And what they found is that that stunted the development of the testes, of the testicles, and it caused testicular atrophy. Now, these were very high doses, but we've got to be a little bit careful. We think, we say, well, melatonin is a natural hormone, so anything natural is safe. Melatonin overall, in terms of its safety profile, is very safe.

• 29:30Dr. Matthew Walker?

  It's actually a very good antioxidant. But you've got to be careful because things like, for example, testosterone supplementation in males, what we know is that if you're injecting testosterone, after a while, after maybe 18 months or so, the testicles themselves will stop producing their own testosterone. And even if you stop the administration of the exogenous testosterone, the injection, the testes never return their function of producing testosterone.

• 30:01Dr. Matthew Walker?

  Now, we don't have any evidence yet that that's the case, that if you keep taking melatonin at high dose, your body, the fear would be, shuts down its own natural production of melatonin. I've seen no evidence of that. In fact, I've seen evidence the contrary, that even after about six months or even 12 months in certain small cities, when you stop melatonin, the production starts again naturally. It seems fine. Problem is, people haven't been taking melatonin for just 12 months. They've been taking it for years. We've got no idea what happens after years.

• 30:32Steven Bartlett?

  That was my hesitation when the first time someone offered me melatonin is, from doing this podcast and speaking to smart people like yourself, I've come to learn this sort of principle that if you start making something for your body in terms of a hormone, if you start sort of consuming something externally, like testosterone, your body will say, fine, I don't need to do this. It'll try and return to that level of balance where the quantities in your system are maintained, which means it kind of learns to shut down. And I always think about the case of testosterone, because men know that if we start injecting testosterone, then we're going to have to pretty much do it forever.

• 31:04Dr. Matthew Walker?

  Yeah.

• 31:04Steven Bartlett?

  If we want those levels to be the same.

• 31:06Dr. Matthew Walker?

  Yeah, that's the worry is that there are no free lunches in biology, and usually if you fight biology, you typically lose.

• 31:13Steven Bartlett?

  There's always a trade off. And some of my friends often like talk to me about like these miracle things, or this thing, or take metafenol and everything will be fine, and da, da, da, da. I go, yeah, but what's the trade off? And I get most concerned when they say, there isn't one. Because then I go, shit, we don't know it.

• 31:27Dr. Matthew Walker?

  Yeah. You've got to be careful because absence of evidence is not evidence of absence.

• 31:33Steven Bartlett?

  Hmm.

• 31:34Dr. Matthew Walker?

  Be very careful when you're doing that deal with with your physiology. So to come back to the sort of the three things, the first thing we were mentioning is digital detox. And don't worry about the blue light. Worry about light in general, I'll come on to that because that's the second, but Michael Gradisar is saying, what he found is that the blue light doesn't really disrupt your sleep. It's a combination of first, these devices that we use are attention capture devices and they are designed to fleece you of your attention economy and they do it ruthlessly well. They've spent tens of millions of dollars designing these products to do that. So what happens is that these devices become hugely activating and as

• 32:19Dr. Matthew Walker?

  a result, they essentially will be a mute button on your sleepiness. So you could be there, you get into bed, it's 11pm, you think, I am so tired, I was falling asleep on the couch watching television. And then you get into bed, you start going on to social media and then you start doom scrolling and then you get into this what we call bed rotting, where you just sit there. And now you look at the clock and it's no longer 11pm, it's 1am and you've just done sleep procrastination. Now, it turns out that it's, yes, that, that these are attention grabbing devices that will mute your sleepiness. But you have to be of a certain personality type, he found. Not all of us are vulnerable to this sleep disruption of devices. You have to be someone who is perhaps neurotic,

• 33:03Dr. Matthew Walker?

  someone who has high impulsivity, or someone who is perhaps high anxious. If you are of any of those kinds, you should be really careful about your use of technology in the bedroom. Now, for me to, you know, sit here and say, look, put your phone in the car in the garage and that way, you know, that's what I would love. Because what we've learned to do in this modern era is the first thing when you wake up, what is it that you do?

• 33:31Steven Bartlett?

  No, no comment.

• 33:34Steven Bartlett?

  Lots of you.

• 33:35Dr. Matthew Walker?

  You.

• 33:37Dr. Matthew Walker?

  It's just you and I, Stephen.

• 33:39Steven Bartlett?

  I grab my phone before my eyes are even open.

• 33:42Dr. Matthew Walker?

  And what happens is this sort of small tsunami of anxiety washes over you. Because as soon as you unlock the phone, it's everyone else's agenda for your day but your own. And it's a terrible way to wake up. Have you ever had the experience where you've got to wake up for an early morning flight and it's a critical flight? You know that that night is not going to be a good night of sleep. It's going to be a shallow kind of sleep. It's what we call anticipatory anxiety. You are anticipating an anxious event in the morning. And studies have shown that when we create this anticipatory anxiety, the amount of deep sleep that you have drops significantly. You don't sleep as well.

• 34:22Dr. Matthew Walker?

  And therefore, if we just do this little sort of version, this L I T E version of the morning flight, which is, we know that when we go to bed and we put our phone down, we know that when we wake up every morning, we're just going to open it up to that hit of anxiety every morning. No wonder our sleep can start to get shallow. Now, I'm not going to sit here and say, well, don't take your phone into the bedroom, because the genie is out the bottle, and no matter what I say, it's not going back in anytime soon. And a friend of mine, Michael Grand, has got this beautiful framework where he says, you can take your phone into your bedroom, it's fine. But you can only use your phone standing up.

• 35:04Steven Bartlett?

  What's his name?

• 35:07Dr. Matthew Walker?

  Michael Grand, he's brilliant.

• 35:09Steven Bartlett?

  Tell him to mind his own business.

• 35:12Dr. Matthew Walker?

  And what happens is that you're there and you think after about seven or eight minutes, I'm just gonna have a bit of a sit down here. As soon as that phone goes away. So I would say that digital detox is the first friend that will really help your sleep. The second is regularity, and we'll come on to regularity when we speak about, you know, what really makes for good sleep. If you were to only do one thing, not three things, but just one thing, go to bed and wake up at the same time, no matter whether it's the weekday or the weekend, regularity is king.

• 35:45Steven Bartlett?

  Okay, so that's the third pillar.

• 35:47Dr. Matthew Walker?

  That's correct, regularity.

• 35:49Steven Bartlett?

  Okay. And then I have the T for timing.

• 35:54Dr. Matthew Walker?

  Correct.

• 35:55Steven Bartlett?

  Which we'll go through these. Quantity, which we've talked a little bit about already, and quality.

• 36:00Dr. Matthew Walker?

  Correct. So, when I looked at the science, for me, I created this framework of the four macros of good sleep. You've heard of the three macros of food, micronutrients, fat, protein, carbohydrate. To me, there are four macros of good sleep, and it's Q, Q, R, T, Q, Q, R, T. And it stands for quantity.

• 36:26Dr. Matthew Walker?

  Quality,

• 36:29Dr. Matthew Walker?

  regularity,

• 36:32Dr. Matthew Walker?

  and timing. And think of it less like pillars, but the four legs of a chair. And if any one of these becomes unstable, the chair will topple over. So I'll probably start with the one that people have had me bang on about, which is quantity. Seven to nine hours. This myth of eight hours is nonsense. It's a wonderful range. Seven to nine hours. And what we know is that using that sweet spot of seven to nine hours, when you get less than that, the shorter your sleep, the shorter your life.

• 37:02Steven Bartlett?

  Fuck.

• 37:03Dr. Matthew Walker?

  Short sleep predicts all-cause mortality. Now, we say that there's the minimum of seven hours of sleep. And some people have argued, perhaps correctly, that, look, if you look at these mortality curves, there's not much of a percentage difference between sleeping six hours versus the seven that you're telling me is minimum. So six hours is just fine. So all of this nonsense and rhetoric is silly from you. And I think they've made a conflation. Because seven hours is the minimum amount of sleep that you need to survive. Because the way that we quantify what minimum is is based on whether you die or you don't prematurely.

• 37:46Dr. Matthew Walker?

  The amount of sleep that you need to survive is different than the amount of sleep that you need to thrive. And people will conflate the former with the latter. So you've got to be careful when people are sort of touting on social media, saying, "Well, no, but look, there's not much difference between my sort of survival rate on six hours versus seven hours." You may have just as much of a long life, but the quality of your life will be very different. So that's quantity, seven to nine hours.

• 38:15Steven Bartlett?

  And is that, does it change for parents, by the way? Because I've met so many parents that seem to be functioning better than me, and they've got four, they're having like four or five hours sleep. Did evolution not give parents any leeway or anything when they have kids that suddenly their brain changes and now they can survive with less sleep?

• 38:30Dr. Matthew Walker?

  The evidence doesn't suggest that once you go through parenthood, you get some magic sort of, you know, immunity shot that makes you, you know, resilient and not vulnerable to a lack of sleep. And in some ways, you could argue because we used to, you know, live as a collective tribe and we would share duties. At that point, you know, Mother Nature doesn't really worry too much about you now because you've already procreated and you've passed on your genetic code. So you are now the, the sort of, you know, the not particularly well, you know, cared for individual through evolution. It's your offspring that gets.

• 39:12Steven Bartlett?

  So it sacrifices you in a way. I mean, that's what we see in the animal kingdom. Did you see that documentary about the octopus?

• 39:18Dr. Matthew Walker?

  Yeah, it was just, I mean, I thought it was a beautiful documentary, but.

• 39:23Steven Bartlett?

  The TLDR for anyone that hasn't seen it is once the octopus, and I'm going to completely butcher this, so please ignore. Once the octopus has given birth, it dies, basically doesn't move out of that hole and it dies? Is that rough?

• 39:36Dr. Matthew Walker?

  Well, I don't know if it dies, but its level of active life.

• 39:40Steven Bartlett?

  I searched, does the octopus die after reproduction? And it says, yes. Female octopuses die after their eggs hatch. After laying eggs, a female stops eating and devotes all of her energy to protecting and oxygenating them until they hatch. Once they do, she dies shortly after, a process called semi-ill parity, meaning they reproduce only once. This death is triggered by hormone changes from the optic gland, similar to mammalian proctoreginal glands. And males die shortly after mating as well, usually within a few months. That is wild.

• 40:18Dr. Matthew Walker?

  In some ways, it's tragic and it reminds me, I'm so glad that I'm not an octopus. But, but coming back to it, so, but there doesn't seem to be some, you know, magic cloak of invincibility that you put on when you go through parenthood. Certainly what we know is that the number of individuals who can survive on six hours of sleep or less and show no impairment in either their brain or their body, rounded to a whole number and expressed as a percent of the population, is zero. So quantity matters, but it turns out that we got it wrong in thinking that was

• 40:58Dr. Matthew Walker?

  the only thing, because then came quality, so Q Q R T. Quality is defined in sleep science as two things. The first is something that your sleep tracker will measure, which is the continuity of your sleep, meaning do you sleep in one or two nice, long bouts throughout the night? That's good quality of sleep, nice, continuous bouts. Versus your sort of sleep is very fragmented by all of these awakenings. That's very poor quality of sleep. And the way that you can measure it in your sleep tracker is just by looking at the app, and there'll be something called sleep efficiency. Sleep efficiency is defined as the following: of the time that you're in bed, what percent of that time is spent asleep?

• 41:41Dr. Matthew Walker?

  And what we'd like to see is you north of eighty-five percent or above. So this is kind of like the user's guide to sleep trackers. What I want to see is eighty-five percent or more. If you're less than that, we need to have a conversation. That's number one, good quality of sleep. The second, which is what sort of what these trackers can't really do, but I can do in the sleep laboratory, when you look like a spaghetti monster because I put electrodes all over your head, I can measure the quality of your big, deep, slow brainwaves of deep non-REM sleep. And that is a second measure, the power of those big, slow brainwaves. That's a second measure. And quality seems to be as predictive as quantity in making a difference, not just

• 42:24Dr. Matthew Walker?

  to your all-cause mortality, but quality, even more than quantity, when it comes to mental health, has been showing the bigger signal. So, again, it's not that quantity doesn't matter. You do have to get sufficient amounts of sleep. But quality, as much as quantity, should be paid attention to. And I haven't said that enough. The next is where we came to in our sort of three things that I was saying. The first is digital detox. Then the next thing I said is regularity. This is somewhere where I've also changed my mind on. I've doubled down on regularity. There was a study that also came out of that same data set that I described. It's called the UK BioBank Data.

• 43:06Dr. Matthew Walker?

  And now they didn't look at 90,000 individuals, but they looked at 60,000 individuals. And they decided that they were going to compare and split them into quartiles. So the most regular to the second most regular to then sort of the third most regular. And then the final quartile was those who were the least regular.

• 43:27Steven Bartlett?

  And what does regular mean in this context?

• 43:28Dr. Matthew Walker?

  Good question. Highly regular individuals plus or minus 15 minutes in terms of going to bed and waking up at the same time. In other words, a total wiggle room of 30 minutes.

• 43:38Steven Bartlett?

  Oh, okay. So if I'm always going to bed at 9:00 PM and I do that five days in a row, I'm not regular timing, really?

• 43:43Dr. Matthew Walker?

  So it's regularity in terms of when you're going to bed and waking up. So you're right, it's timing in a way. But I'll come on to why there is a separate T for timing in just a second. But regularity here was, okay, plus or minus. So let's say you go to bed at 8:45 PM one night and then 9:00 and then 9:10 PM. And then you're back to 8:00. That's beautiful, tight timing. I like that. Whereas those people who were least regular, they were 90 to 120 minutes disparate. They were going to bed, let's say, at 11:00 one night, then 1:00 AM the next night. Then they were going to bed at 10:30 PM and then they were going to bed at 12:30. They were all over the map.

• 44:24Dr. Matthew Walker?

  So what they found was that those people who were most regular versus least regular. So they compared the extremes of these two. Those people who were most regular had a 49% relative decrease in all-cause mortality. So they were 49% less likely to prematurely die than those people who were least likely to die. They had a 39% cancer mortality risk reduction. Great. They had a 57% cardiometabolic disease risk reduction. So that was stunning, that regularity was incredibly powerful as a predictive signal of your different forms of mortality. That wasn't the best part of the paper, though.

• 45:10Dr. Matthew Walker?

  They had also measured quantity as well as regularity in these same individuals. So then they decided to say, well, I'm going to take our measure of quantity and regularity. And we're going to put them both in the same statistical bucket and do a Coke Pepsi challenge to see which one wins out in terms of predicting all cause mortality. We all bet in the sleep field, or at least I did, it was going to be quantity. I was wrong. Regularity beat out quantity in predicting all cause mortality and by quite some margin. Now, that doesn't mean that you can now go away and say, I'm going to start sleeping four hours, but incredibly consistent four hours. You need both quantity and quality, but goodness, does regularity seem to carry a massive signal?

• 45:54Dr. Matthew Walker?

  So coming back to those three things, I would say digital detox, just go to bed and wake up at the same time. And the final thing is light. In this modern world, we are a dark, deprived society. We get what I call junk light at night. So you've heard of junk DNA? Well, we get junk light at night. We don't need all of this light and it fools our brain into thinking it's still daytime outside. So no wonder as a society, we have some struggles with sleep at night. Now, that's due to many reasons, stress, too much caffeine, alcohol, THC. But excessive light is one of the easiest things that you can do. So for the next seven days, just do me this experiment.

• 46:37Dr. Matthew Walker?

  If you can, set an alarm one hour before your normal bedtime. When that alarm goes off, turn off, and I do this myself, turn off almost all of the lights in your house.

• 46:50Steven Bartlett?

  When you say all of the lights, do you mean the little red light on my smoke alarm?

• 46:54Dr. Matthew Walker?

  No, that's fine. But you know, so my wife and I, one hour before bed, almost all the lights, we've got sort of this little set of this sort of light that goes around the television, the back of the television, so it kind of looks like the television's cool and illuminated. I will set that down to about five percent of brightness. And all of the rest of the lights out, so you can kind of just still see some illumination. So I'm not sort of, you know, looking desperately uncool in front of her when I'm tripping over things because it's complete black, you know, then start cooling the house or the room as best you can to around about sixty seven, sixty eight degrees Fahrenheit or about eighteen degrees Celsius. We can speak about temperature, but just do this experiment for the next

• 47:35Dr. Matthew Walker?

  seven days. One hour before bed, the alarm goes off, you switch off all of the lights and ask the following question. Do you feel sleepier? Is it soporific? Does it make you feel more sleepy as a result? But don't stop there. What you've gone and done is the first positive experiment, which is you've gone from the no intervention, lights are on, to then the Matt's intervention, which is now the lights are off for one hour before bed. Don't just ask, is my sleep better when the lights were out for one hour before bed? Once that seven day period has finished, go back to doing what you were doing before, which is keep all of the lights on and ask yourself, did my sleep get better when I

• 48:18Dr. Matthew Walker?

  did the intervention? And did my sleep go back to being worse when I stopped? Because I'm trying to teach you bidirectionality in the experiment. Does that make some sense?

• 48:27Steven Bartlett?

  Yeah, so you get to, you get to basically do an A B test.

• 48:30Dr. Matthew Walker?

  Correct. You get to see both sides of the equation. And with that, it's more proof positive than just one direction alone, because who knows, it could just be a placebo effect. So regularity, coming back to it, is critical. So we've spoken about Q Q R, quantity, quality, regularity.

• 48:47Steven Bartlett?

  On the

• 48:48Dr. Matthew Walker?

  Regularity.

• 48:49Steven Bartlett?

  Regularity point, why? What's going on in our brain that's making it, from a hormonal perspective or other, that's making it important for us to sleep at the same time?

• 48:59Dr. Matthew Walker?

  It's a bloody great question. People don't respond to rules. They respond to reasons, not rules. So let me try and explain the reason behind the sort of the rule. When it comes to regularity, we have something called a circadian rhythm that we've spoken about. And there's a clock that sits inside of your brain, deep in the middle of the brain. So we have, it just turns out, a brain here.

• 49:25Dr. Matthew Walker?

  Lovely. Okay, so we've got one of these hemispheres here. And then I'm just going to take out what we call the subcortical sections. So these are the areas that are below the subcortex. So here is the brain. So this is the front of the brain, the back of the brain, top of the brain. And here's the brain stem. And it turns out that right in the middle of the brain, right here, there's an area called the hypothalamus. Now here, this structure here, this is the thalamus. This is the sensory gate of your brain. So all of your five senses, sound, touch, taste, smell, they all flood into this gate called the thalamus. And then the thalamus will decide whether it sends those sensory signals up to your cortex. And when it sends the signals up to your cortex,

• 50:07Dr. Matthew Walker?

  you start processing them and you become consciously aware of the external world. Now, as we're falling asleep, just as an aside, what's interesting is that this gate, the sensory gate, the thalamus, once we start to fall asleep, the gate will close shut. Now, your eyes are technically still seeing. Your ears are still hearing. Your tongue is still tasting. But because the gate of the thalamus, the sensory gate closes shut, those signals that are coming into your brain are no longer sent up to your cortex. So you stop perceiving the outside world, which is just simply a different way of saying you've fallen asleep. Now, the hypothalamus, you've heard of hypo, sort of hypertension

• 50:49Dr. Matthew Walker?

  or sort of, you know, hypothermia, that means lower. So here's the thalamus. This area here is called the hypothalamus. And it's a tiny structure, but within that structure contains a nucleus. And that group of cells, the nucleus, has a fancy term and it's called the suprachiasmatic nucleus. But the suprachiasmatic nucleus is your master 24-hour clock. Every cell in your body has a clock inside of it.

• 51:19Dr. Matthew Walker?

  But this is the master clock. It's like Lord of the Rings. There's one ring to rule them all. Well, there's one clock to rule them all. And here, in the suprachiasmatic nucleus, you get the 24-hour rhythm of being awake and being asleep, being awake and being asleep. How does your brain keep quartz-like precision 24-hour clock time? How does it do that? The way it does that is that it uses signals such as light and dark.

• 51:48Steven Bartlett?

  From your eyes.

• 51:49Dr. Matthew Walker?

  From your eye. And so when light comes through the retina, it tells the hypothalamus it's daytime, and therefore you should be awake. And its rhythm starts its awesome sort of upswing. And temperature can do this, and feeding can do this, all sorts of different things. But for the most part, light is the principal governor that essentially acts like electrical, I should say, photon fingers, that pops the wristwatch dial out and resets it precisely to 24 hours every single day. Because if you're left in the dark with no signals of light, your clock isn't precise. It drifts to about 24 hours and 15 minutes. So you start going forward a little bit every single day if you go into a cave, and people have done this experiment.

• 52:33Dr. Matthew Walker?

  The thing that keeps it precise is light. So you need light to keep a beautiful 24-hour rhythm. One of those things that's under the control of your 24-hour rhythm is your sleep-wake cycle.

• 52:46Steven Bartlett?

  What if I'm doing exercise?

• 52:47Dr. Matthew Walker?

  Exercise is a wonderful entrainer of your circadian rhythm as long as you're doing it at the right time. So if you're starting to exercise at 3:00 or 4:00 in the morning, that's not good, because that's an activity signal that's going to confuse the brain into thinking it's the active period, which is normally, because we're a diurnal species, the day. And it's the same thing, coming back to my point of regularity, using light as the best way to help with that regularity, because light... If it's artificial at night, fools your brain into thinking that it's daytime still outside.

• 53:24Steven Bartlett?

  I mean, is there any such thing as non-artificial light? I mean, I guess with the sun, but I mean, is there a type of light that I could use at night like candles or something?

• 53:32Dr. Matthew Walker?

  Yes, below thirty lux.

• 53:35Steven Bartlett?

  Right.

• 53:35Dr. Matthew Walker?

  Is not going to necessarily do you a disservice, probably below fifty lux. Now lux, L U X, is just a measure of light intensity. And you can download on the App Store a free lux meter. And if you're an idiot nerd like me, you're going all over the house at night. And you're sort of putting it in different location, you're seeing if there are any kind of white spots here where, you know, the lux is too high. But you need to drop that that lux. By the way, it's a great way, if people want to say, look, my REM sleep is deficient. How can I get more REM sleep? There's a great study where they did something similar to what I'm telling you now. Ninety minutes before bed, they turned down the lights to below thirty lux. And they pulled out all of the blue light.

• 54:18Dr. Matthew Walker?

  And just that trick of dropping the lights down ninety minutes before bed, below thirty lux. Making it warm yellow light increased their REM sleep by eighteen percent.

• 54:29Steven Bartlett?

  Wow.

• 54:29Dr. Matthew Walker?

  It's a huge margin, so no need for pharmacology. But to your question, why is regularity important? Well, I told you that light is one of the signals that can create regularity. It turns out that your behavior is another thing that will tell your brain. So meaning, when you go to bed and wake up at the same time, it acts like an anchor. It anchors your circadian rhythm. And it tells you, almost like a scene in a movie, this scene is now complete and new scene starts. This scene is complete and new scene starts. So every time that you're going to bed at the same time and waking up at the same time.

• 55:10Dr. Matthew Walker?

  You are feeding the suprachiasmatic nucleus, the master twenty-four hour clock in your brain. You're feeding it signals of regularity. And when it feeds on signals of regularity, it improves the quantity and the quality of your sleep.

• 55:28Dr. Matthew Walker?

  Your circadian rhythm likes consistency. It likes regular signals. When you feed it signals of light, of activity, of waking up, going to bed, you improve the quantity and the quality of your sleep. That's the reason behind the underlying rule.

• 55:43Steven Bartlett?

  So having a TV in your bedroom is a terrible idea then? Because if, on that behavioral point, if I'm getting in bed, but then I'm staying up for three hours watching Netflix, my brain is going to be quite confused about like the behavioral pattern of what I'm doing in my life. It's not going to associate the bed with sleep. It's going to associate the bed with movies.

• 56:02Dr. Matthew Walker?

  That's one of the problems that we call, it's called conditioned arousal, which sounds a lot more salacious than it actually is. It's a term that we use in sleep medicine, which may explain insomnia. So with insomnia, let's say that the first time you go to this thing called a dentist and you get in the chair and it's kind of cool, you recline back and you know, you think this is fine. But then after about 14 or 15 visits, when you get into that chair, you are no longer looking forward to getting into that chair, are you? Why? Because you've learned the association that being in that chair typically leads to a bad outcome. Now, the same thing is true with the bed.

• 56:44Dr. Matthew Walker?

  If you start associating the bed with anything other than sleep, and we give you a pass in terms of sex, but sleep and sex, anything other than that, you start to learn that this thing called my bed is this place where I'm awake, where I work, where I eat, where we have conversations, where I watch television. And so, you know, if I were to, and I'm stealing Michael Grenner's point, but if I were to say to you, bed, sleep, bed, sleep, bed, sleep, bed, sleep. Okay, if I were to say, bed, scroll, bed, eat, bed, work, bed, sleep, bed, TV, bed.

• 57:23Dr. Matthew Walker?

  You've confused.

• 57:25Steven Bartlett?

  Yeah.

• 57:25Dr. Matthew Walker?

  Because there's no predictive signal. You've never bound an association. Now, the way this works to your disadvantage in insomnia is the following. The insomnia event that begins the insomnia is typically not the thing that maintains the insomnia. So let's say that I had, I experienced a really difficult bereavement. And that triggered a form of insomnia where I couldn't sleep because of the bereavement. Gradually, the bereavement is not the thing that's going to maintain my insomnia. It's because every time I have been going to bed over the past month, I have not been sleeping. I've been wide awake in my bed.

• 58:07Dr. Matthew Walker?

  So now, because your brain is such an incredibly associative device, it learns the association that my bed is the place where I'm always awake. And what do we then do? We need to break that association in insomnia. So what we do is we say the 20 minute rule. If you've been in bed for about 20 minutes and it's just not happening for you, don't worry, don't listen to idiots like me that doom and gloom and disease and sickness. And one bad night is not going to be a problem. It's just not. So just say, look, tonight is not my night. I am not, however, going to lie in bed awake. Because very quickly, my brain starts to learn the association that my bed is the place where I'm wide awake. And you need to break that association. So go to a different room in dim light, just read a book, listen to a podcast, whatever it is.

• 58:52Dr. Matthew Walker?

  And the rule of thumb is the following. Only return to bed when you are sleepy. And so there's no time limit. And that way, you gradually relearn the association that my bed is the place where I always get consistent sleep. Because otherwise, it's the dentist's chair. You walk into your bedroom and you look at your bed and it's your nemesis. And you convince yourself, even before you get into bed, I'm not going to sleep because that's the place where I always don't sleep. And by the way, if you suffer from the three M awakenings, my first question is, how do you know it's 3am?

• 59:26Dr. Matthew Walker?

  And that's your first problem. Looking at the clock does two things. It makes you more anxious.

• 59:31Steven Bartlett?

  Yeah.

• 59:32Dr. Matthew Walker?

  And second, because your brain is such an incredibly associative device, you start to then decide that 3 a.m. is the time when I need to wake up. If you keep looking at the clock, you keep reinforcing that it's 3 or 4. And sleep at 3 o'clock in the morning is like trying to remember someone's name. The harder you try, the further you push sleep away. Sleep is something that happens to you. It's not something that you make happen. And so at that moment, the best advice, if you don't want to get out of bed, is do any one of the following. Meditation. Just do a guided meditation. You can download apps. Next, if that's not your thing, that's okay. Do box breathing.

• 1:00:14Dr. Matthew Walker?

  You know, you can sort of inhale for five, hold for six, exhale for seven. There's all sorts of different numbers, but you can do breathing exercises. The third, if you don't like that, is a body scan. So close your eyes, start at the top of your head. Feel, you know, do I have tension in my forehead? Do I need to relax it? What about my neck? Do I need to? Move through your body and gradually go down. How are my shoulder blades feeling? Just relax down into the bed and gradually down into the chest, into the... Move through and just relax. If none of those things feel fun, the next thing you can do is take yourself on a mental walk. There's a great study from my university, the University of Berkeley, California. And we didn't do the study, Alison Harvey did it. By the way, counting sheep? Bad idea.

• 1:01:00Dr. Matthew Walker?

  Makes your sleep worse, it turns out. Why is that? Because, well, with every kind of little bleating cotton wool ball with a strange look on its face that leaps over the fence that you're counting, you're reinforcing every minute of sleep that you're not getting, and it seems to make matters worse. But what she found was that there's an alternative. If you think about a walk that you know in great vivid detail... So for me, it's going to be walking the dog. So I go over to the shelf, I open the door. Is it the red lead or the...? I'm gonna go with the blue lead today. So I clip the dog in with my right hand, I open the door with my left hand, I take a left down the stairs, I look. It's that level of, I want you 4K detail in terms of granularity.

• 1:01:41Dr. Matthew Walker?

  And what's common about every method I've just described, meditation, box breathing, sort of body scan, going on a mental walk, all of these things have in common that you get your mind off itself.

• 1:01:56Steven Bartlett?

  In that particular example where she asks you to vividly think about a journey that you know, what did she find in the study?

• 1:02:03Dr. Matthew Walker?

  What she found is that that increases the speed with which you fall back asleep significantly. Because, as I said, it's so, you know, her work to me demonstrated that it is so like that name because the moment I stop trying to remember someone's name, what happens?

• 1:02:24Steven Bartlett?

  You remember it.

• 1:02:25Dr. Matthew Walker?

  I remember it. And so when you do these types of exercises where you're getting the mind off itself, the next thing that you typically remember is your alarm clock going off in the morning.

• 1:02:36Steven Bartlett?

  Is this why people listen to very vivid sleep stories and why I listen to serial killer documentaries?

• 1:02:45Dr. Matthew Walker?

  Serial killer documentaries?

• 1:02:47Steven Bartlett?

  True crime documentaries, I should say, that's a bit more nice to palate.

• 1:02:53Dr. Matthew Walker?

  I don't know of them. My suspicion is that they may be doing your deep sleep a disservice.

• 1:02:58Steven Bartlett?

  Stick up for me in the comments. If you listen to true crime to fall asleep, please write it below in the comment section.

• 1:03:06Dr. Matthew Walker?

  If you find it, subjectively, wonderfully pacifying and calming, and there is not death, maiming, blood and limbs being distributed at high velocity all over the scene, I would say it's great. But if it looks like a Quentin Tarantino movie or sounds like one, maybe harm and foul rather than no harm.

• 1:03:27Steven Bartlett?

  I mean like just in my ears.

• 1:03:28Dr. Matthew Walker?

  But yes, so, you know, we forget that, to the best of my knowledge, the meditation company called Calm, now I have no affiliation with them, they were doing somewhat well. But what they realized is that they wanted people to sort of meditate in the morning. And when they looked at their usage statistics, people were meditating in the morning, but then there was a huge swath of usage right before bed. People were self-medicating their state of insomnia. And then through a stroke of genius, they realized, when we were young, we used to love falling asleep to our parents reading us a story. Why is that any different when we become adults? So they created sleep stories and they went from struggling as a company, I think,

• 1:04:11Dr. Matthew Walker?

  to becoming the first or one of the first billion dollar valuation health companies out there. They became a unicorn. And now they can, they've got, you know, people like, you know, Matthew McConaughey, they've got Harry Styles and then occasionally they've got a, you know, an unfortunate British sleep scientist with a bad voice, but you can listen to these sleep stories and they are wonderfully soporific. Why? Because they get your mind off itself.

• 1:04:36Steven Bartlett?

  We talked earlier on about melatonin and that there are other supplements which people talk a lot about. One of the ones that's become really popular is magnesium. I've heard ashwagandha and I've had magnesium a lot.

• 1:04:48Dr. Matthew Walker?

  Yeah.

• 1:04:49Steven Bartlett?

  Is there any efficacy to these? Are these useful?

• 1:04:51Dr. Matthew Walker?

  The first thing I would say is that if you're suffering from sleep problems and you're looking to supplements, you're stepping over dollars to pick up pennies.

• 1:04:59Steven Bartlett?

  Okay.

• 1:05:00Dr. Matthew Walker?

  What you need to do is think about the fundamentals, regularity, what's your caffeine intake, make sure you're not drinking too much alcohol, get regular, dim down half the lights, digital detox, any one of those, but especially all of them combined, are going to get you long orders of better sleep than reaching for the latest supplement bottle of whatever it is. The second thing to say is think about it from a logical standpoint. If there were really some supplement that promises to be the Shangri-La of all resplendent sleep at night, the drug companies would have been all over it decades ago. To put it in context, it took George Lucas, I think, about 30 years to amass something

• 1:05:44Dr. Matthew Walker?

  like four billion in revenue from the Star Wars franchise. It took Ambien 22 months. That's how big a business sleep pharma is.

• 1:05:54Steven Bartlett?

  Ambien's what, a sleep pill?

• 1:05:55Dr. Matthew Walker?

  Ambien is a sleep pill. Magnesium, if you dig into it, and I did a deep dive about three years ago, because I kept hearing it too, this magnesium, magnesium. The first thing to note is that most forms of magnesium, magnesium oxide or magnesium citrate, most of these forms of magnesium don't cross the brain barrier.

• 1:06:17Dr. Matthew Walker?

  And sleep is produced by your brain. So how can something that doesn't get into your brain affect a brain process? Number one, there is one form of magnesium that seems to have some evidence in favor of it. It's called magnesium L three on eight. But if you look at the literature, where did this story come from? It turns out that about 30 years ago, they started looking at people who had disrupted sleep and they would assess their blood work. And what they found is that some of those people were magnesium deficient. And when they supplemented them with magnesium and they became magnesium normative, their sleep got better. But that's very different than saying, look, you and I were currently magnesium normative.

• 1:07:02Dr. Matthew Walker?

  And then dosing myself with high volumes of magnesium. Am I imagining that that's going to make my sleep better? The analogy would be, let's say I developed this incredible new oxygen saturation machine. And you say to me, well, but Matt, my blood oxygen saturation right now, looking at my device tells me it's 98.6%. It doesn't matter how fancy or good my machine is, I'm not going to get you past 100%. You're already at ceiling level. And that's the problem with magnesium supplementation. If you're magnesium normative, all you're doing is creating probably expensive urine at that moment in time. Now, there may be an indirect benefit of magnesium in that it does seem to relax muscles.

• 1:07:47Dr. Matthew Walker?

  And when the body is in a state of relaxation, it sends a signal of relaxation back up a branch of nerves called the vagus nerve that goes up to the brain and signals to your brain, you're starting to relax down and you get this state of quiescence. And that's very helpful for sleep. So magnesium may still have an indirect benefit on sleep through its relaxation kind of policy that it instantiates in the body. But overall, magnesium is not really moving the needle if you look at the studies. Ashwagandha. Is different ashwagandha and another compound called phosphatidylserine, phosphatidylserine and ashwagandha.

• 1:08:30Dr. Matthew Walker?

  Both of these supplements seem to help do one of two things. They either ratchet down the fight or flight branch of your nervous system, and they can also reduce the amount of cortisol that the body is releasing. That's important because I see a lot of people coming to the sleep center where I'm at, and they have what I call the tired but wired phenomenon, where they come to me and they say, I am so tired. I am so, so tired, but I'm just so wired emotionally and from a nervous perspective that I can't fall asleep. And let's say that you've done, let's say, you know, an onstage event, and it's incredible. You've got that onstage buzz. You come offstage at 11pm and normally you'd be fast asleep, but you know you

• 1:09:15Dr. Matthew Walker?

  are so wired, it doesn't matter. You are tired as tired as can be, but you're so wired, you can't fall asleep. That's the fight or flight branch being switched on, and you just can't fall asleep. You need to push it back off. Phosphatidylserine and ashwagandha will both push you back over into the more quiescent, what we call parasympathetic nervous system branch. That's good. However, they also will reduce cortisol, and cortisol is a wake promoting hormone. Cortisol is fine. We get a bad rap. You need to have your cortisol start to spike a few hours before bed, and it helps with the waking up process. It's wonderful. Every day, we have a cortisol spike that starts happening before we wake up. It's one of

• 1:09:59Dr. Matthew Walker?

  the things that helps us wake up, and then it builds us to this beautiful crescendo mid morning, where you should be awake and not needing caffeine. And it drops before bed. And then it starts to peak in the sort of middle early afternoon, and in fact, usually peaks at the late morning hours, I should say, and then it will start its awesome sort of downswing. And what you see is that right before you go to bed, cortisol should hit its lowest point, what we call its nadir, its lowest trough. What's interesting, by the way, just as an aside, is that insomnia, we can classify usually as at least one of two different types. There's actually multiple, but let's just say there are, of those multiple, there are two types. One is

• 1:10:43Dr. Matthew Walker?

  called sleep onset insomnia. I can't fall asleep. The other is sleep maintenance insomnia. I can't stay asleep. When they've looked at people's cortisol on a 30 minute by 30 minute basis on the 24 hour clock face, we go through just what we described. Just before we wake up, we get this rise in cortisol. It peaks late morning and then it drops down and right before bed, our cortisol is almost at its lowest point. With insomnia patients, they show exactly the same thing. A beautiful rise in the late morning hours. It starts to come down, but then you see two anomalies. Right before bed, it goes back up. And then in the middle

• 1:11:25Dr. Matthew Walker?

  of the night, even when it's starting to rise, it will have this abnormal spike right in the middle of the night, too. And what we believe is that that may in part explain sleep onset insomnia. Cortisol should be coming down and it should stay low right before we go to bed, but then it jumps back up in insomnia patients. I can't fall asleep. And then it continues to stay low throughout the first half of the night, but then it also spikes in insomnia patients. I can't stay asleep.

• 1:11:52Steven Bartlett?

  I've had so many founders speak to me and say, why didn't this particular ad that I ran on this platform work for me? Maybe the copy wasn't good, the creative wasn't strong, but usually the problem is they're not having the right conversation because that ad never reached the right person. And if you're in B2B marketing, that is much of the game. And this is where LinkedIn Ads solves that problem for you. Their targeting is ridiculously specific. You can target by job title, seniority, company size, industry, and even someone's skill set. And their network includes over a billion professionals. About 130 million of them are decision makers. So when you use LinkedIn Ads, you're putting your brand in front of the right people. And LinkedIn Ads also drive the highest B2B return on ad spend across all ad networks in my experience. If you want to give them

• 1:12:37Steven Bartlett?

  a try, head over to LinkedIn.com/diary. And when you spend $250 on your first LinkedIn Ads campaign, you'll get an extra $250 credit from me for the next one. That's LinkedIn.com/diary. Terms and conditions apply. We were talking about regularity, timing and all these things and quality and quantity. But one of the things I learned from your work is that that last hour is potentially the most important hour of me being in bed. And I say this in part because my girlfriend, she would wake, she would have about six, six hours, six and a half hours sleep. She sleeps very, very well, perfect sleeper. But she'd always get up really, really, really early. And in part, that was because of the guilt that I talked about.

• 1:13:21Steven Bartlett?

  But I had a conversation with her about the guilt and I said, just stay in bed as long as you need to stay in bed, like just have that extra eighth hour. And in part, that's because I learnt that the further we go in sleep, the more REM we're getting.

• 1:13:34Dr. Matthew Walker?

  Yeah.

• 1:13:34Steven Bartlett?

  Okay, can you explain that to me with these four blocks? Why that last hour is particularly important and why we shouldn't be jumping out of bed? Or why we should be using certain sleep devices to wake us up when we're at the end of that last hour of REM?

• 1:13:46Dr. Matthew Walker?

  Absolutely. So here we have the four blocks of sleep. So when we first fall asleep, we go into light, non-rapid eye movement sleep, stage one. This is the stage of sleep that if I wake you up out of it, you say, I wasn't sleeping. Now, it's just that you're just in that transitional phase, this beautiful liminal state between the windows of wakefulness and true sleep. So this is your bridge between the waking world and the sleep world. And it doesn't last for very long, maybe just 10 or 15 minutes at tops. Then you get into the workhorse of sleep. This is stage two non-REM sleep. Fifty percent of your night is spent in stage two non-REM sleep. I don't like the word light, non-REM sleep.

• 1:14:31Dr. Matthew Walker?

  I've often used it, but it's not really, it's, we do a lot of cognitive processing in stage two non-REM sleep. It's good stuff. It's not just the stage that you have to go through from sort of, you know, deep non-REM sleep to go back to stage two in order for you to get to REM, but I'll come to that. So we have fallen asleep 10 minutes.

• 1:14:51Steven Bartlett?

  Yeah.

• 1:14:52Dr. Matthew Walker?

  Now we're in stage two non-REM sleep. We'll stay there for about 15 or 20 minutes. Then if it's in the first couple of hours of the night, we go down into the very deeper stages of deep non-REM sleep. This is where the brainwave patterns slow down, but the brainwaves become incredibly big, huge, big, powerful, slow brainwaves. This is where you get an enormous amount of restoration, recovery of many of your major physiological systems.

• 1:15:21Steven Bartlett?

  Physical recovery.

• 1:15:22Dr. Matthew Walker?

  Physical recovery, but mental too.

• 1:15:25Steven Bartlett?

  Yeah.

• 1:15:25Dr. Matthew Walker?

  It's during deep sleep that you take newly minted memories that you've learned and you hit the save button on those memories so that you don't forget. Deep sleep essentially is going to future proof the information that you just learned today. It transfers information from a short term, storage vulnerable reservoir to a more permanent long term, storage site. It's during deep non-REM sleep when we have this communication. So think of those deep, powerful, slow brainwaves like long wave radio station when you used to tune into a radio station in the car. You get huge ability for information transfer across long distances, across huge paths in the brain. It's amazing.

• 1:16:08Dr. Matthew Walker?

  So we've gone from light non-REM, then we go down into deep non-REM, we'll stay there for about fifteen or twenty minutes, then we'll start to rise back up again, we'll go back into stage two non-REM sleep.

• 1:16:19Steven Bartlett?

  Wait, we've gone from one, two, three to two?

• 1:16:21Dr. Matthew Walker?

  Yes. So we've gone, think about it more, almost like a roller coaster ride. So we go from light non-REM, and then we go down into stage two non-REM, then we go down into deep sleep, and then we're going to rise back up into light, stage two non-REM sleep. We're going to stay there and after about seventy, eighty minutes, you're going to pop up and you'll have a short REM sleep period.

• 1:16:47Steven Bartlett?

  Oh, okay, like this?

• 1:16:48Dr. Matthew Walker?

  And this is beautiful. So this is what we call a hypnogram.

• 1:16:53Steven Bartlett?

  I'll put this on the screen for anyone.

• 1:16:54Dr. Matthew Walker?

  Lovely. So what I'm describing here is this roller coaster ride. So we've fallen asleep, light stage one, non-REM, go down into stage two, then you go down and you have a heavy period of deep, non-REM, slow wave sleep, stage three. And then, and that's what you see on your sleep tracker is deep sleep. This is light sleep, this is deep sleep, stage two, non-REM sleep, light sleep, stage three, non-REM sleep, deep sleep. But then you'll start to climb back up and then you may pop up and you'll have a short REM sleep period here after about seventy or eighty minutes. So you'll have about ten minutes of REM sleep and then back down you go again. You go down into non-REM sleep and then up into REM, down into non-REM sleep and you'll go up into REM, down into non-REM sleep and up into REM.

• 1:17:39Dr. Matthew Walker?

  So what's interesting, however, is that the ratio of non-REM to REM changes. Now, there's a myth out there, and it's a bit of a problem. We humans have a 90-minute average non-REM to REM cycle. So we go down into non-REM sleep and then up into REM sleep every 90 minutes. Then we go back down into non-REM sleep and then up into REM sleep. So we go down into non-REM sleep and then up into REM in this 90-minute cycle. The problem is that it's, on average, 90 minutes. It ranges from 70 minutes to up to 120 minutes from one individual to the next. So you know these devices that you may have seen, tried to sort of, you know, entrepreneurship.

• 1:18:21Dr. Matthew Walker?

  They say, "I'm going to wake you up at the ideal moment in your 90-minute cycle." So that this thing that sits on my bedside, I tap it when the lights go out, and then it's going to go on its 90-minute cycle, and it's going to figure out the perfect moment to wake you up. It's nonsense, because my sleep cycle may be 75 minutes. Yours may be 105 minutes. It's got no idea, because it's using a hardcoded 90-minute cycle. It's, in some ways, nonsense. But we go down into non-REM sleep and up into REM sleep every 90 minutes. What changes, however, is the ratio of non-REM to REM within those 90-minute cycles as you move across the night, such that in the first half of the night,

• 1:19:03Dr. Matthew Walker?

  the majority of those 90-minute cycles are comprised of lots of deep non-REM sleep and very little REM sleep. But as you push through to the second half of the night, now that seesaw balance shifts over, and you spend much more of your time in REM sleep in the second half of the night, and particularly, just as you said, in the last two hours of the night. Why is this consequential? Well, just as you said and you spoke about for your girlfriend, let's say that, you know, I normally go to bed for argument's sake, and I'm not saying this is the ideal time, but I go to bed at midnight to make the math easy, and I wake up at 8. But tomorrow, I've got to catch my flight back home. So I'm going to wake up two hours early. So I'm going to wake up at 6 rather than 8. I've lost two hours of sleep. So how much total sleep have I lost?

• 1:19:47Dr. Matthew Walker?

  Well, I've lost 25% of my total sleep. Two hours of my eight hours, 25%. Well, yes and no. I've lost 25% of my total sleep. But I may have lost fifty, sixty, seventy percent of all of my REM sleep. Why? Because REM sleep comes in the second half and particularly those last couple of hours of sleep. So that's why it's not just academic that you understand the sleep cycle relationship. But it's also pragmatic because it can impact the amount. In fact, the easiest way, if people said, how can I get more REM sleep? I would say just sleep fifteen minutes later into the day than you normally would do. And you will disproportionately bias yourself towards getting significantly more REM sleep. And why does REM sleep matter?

• 1:20:32Dr. Matthew Walker?

  REM sleep is a brain state firstly that is incredibly active. In some, in fact, some parts of the brain, particularly if I were to show you these deep emotional centers of the brain. Let's say pull this brain apart. So we've got these sort of deep emotional centers in the brain that sit. And in fact, the sort of, they're more just underneath in here tucked in inside, just next to your brain stem at the top of it. And these emotional centers are called the amygdala. And you have one on the left and one on the right side of your brain. That part of the brain, together with a memory structure that runs alongside it called the hippocampus. Those two parts of the brain form what we call the limbic system. And you may have heard of the limbic system, the emotional centers of the brain.

• 1:21:15Dr. Matthew Walker?

  Those can be up to forty percent more active when you're in dream sleep than when you're awake. Dream sleep? Dream sleep is rapid eye movement sleep. REM sleep. So REM sleep is the stage now, it depends on how you define dreaming. If you define dreaming as any mental activity reported upon awakening, then you dream in all stages of sleep. Light non-REM sleep, deep REM sleep. So what would, what would that sound like? Well, if I woke you up and said, Stephen, just tell me what was going through your head. And you said, well, I was just thinking about the next time you're going to come in and wake me up. That's just a dream thought. The most people think of dreams as the dreams that we have from REM sleep, from rapid eye movement sleep. That's why we call it dream sleep. Dreams from rapid eye movement sleep are florid, they're narrative.

• 1:21:59Dr. Matthew Walker?

  In fact, last night, when you fell asleep and you went into dream sleep, you became. Incredibly psychotic.

• 1:22:07Steven Bartlett?

  Excuse me?

• 1:22:08Dr. Matthew Walker?

  Now, before you reject my diagnosis of your nighttime psychosis, let me give you five good reasons. When you went into dream sleep last night, you started to see things which were not there. So you were hallucinating. Second, you believe things that couldn't possibly be true. So you were delusional. Third, you became confused about time, place, and person. So in psychiatry, we call that being disorientated. Fourth, you had wildly fluctuating emotions, something that we call being emotionally labile. You're all over the place. And then, how wonderful. You and I, because I'll include myself now as being psychotic, you and I, we both woke up this morning and we forgot most, if not all, of that dream experience. So we're suffering from amnesia.

• 1:22:52Dr. Matthew Walker?

  If you were to experience any one of those five symptoms whilst you're awake, you'd be seeking some degree of psychological help. But for reasons that we're only now understanding, it seems to be a normal biological and psychological process. So what are the reasons? Why do we dream? We dream for at least two different reasons. The first reason is emotional first aid. REM sleep is what I've defined as overnight therapy. And it's during dream sleep where your brain takes difficult, painful emotional experiences. And it acts like a nocturnal soothing balm. And it just takes the sharp edges off those difficult, painful experiences so that you come back the next day and you have a memory of an emotional event.

• 1:23:36Dr. Matthew Walker?

  But it's no longer emotional. You don't have that same visceral regurgitation of that same emotional charge. Why is REM sleep able to do this overnight therapy? This depotentiation? Why is REM sleep able to sort of strip the bitter emotional rind from the informational orange, as it were? The reason is the following. Dream sleep, REM sleep, is the only time during the 24-hour period where the brain shuts off a stress-related neurochemical called noradrenaline. Now, you've heard of the sister chemical downstairs in your body called adrenaline. Well, upstairs in the brain, we don't have adrenaline. We have noradrenaline. REM sleep is the only time where it's completely shut off.

• 1:24:22Dr. Matthew Walker?

  And what we put forward is a theory called overnight therapy, where your brain has, as I told you, these emotional centers, and these memory centers, the emotional centers, the amygdala, the memory centers, the hippocampus. You reactivate those structures when you go into dream sleep. So your brain gets the chance to reactivate and replay and reprocess emotional experiences. However, it's doing it in a quote unquote "safe neurochemical environment", because that stress chemical of noradrenaline is completely shut off. So it's the ideal neurochemical therapy for stripping the emotion from the memory. And we put forward a theory that perhaps the quintessential disorder where this fails is PTSD.

• 1:25:07Dr. Matthew Walker?

  Because when you speak to those patients, not only do we see that their REM sleep is disrupted, when you speak to those patients, they will say, "Look, I just can't quote unquote 'get over the event'". What they mean by that is, the war veteran who is now going to the supermarket, and they come outside, and they're in the car park, and the car backfires, and they instantly have the flashback to the detonation on the military field. And what's happening there is that the brain has not stripped the emotion from the memory. So every time they relive the memory, they regurgitate that same emotional reaction. So no wonder we propose that the brain then comes back the following night and says, "Look, I'm sorry, sleep.

• 1:25:52Dr. Matthew Walker?

  I've still got this trauma memory. Can you do your trick of stripping the emotion from the memory?" And it fails again. So in the next night, it comes back and says, "I'm sorry to bother you, but I've still got this emotionally charged memory. Please do your trick of stripping the emotion from the memory." It fails again. This sounds like the broken record of repetitive nightmares that we see in PTSD. Why could this be happening? Levels of noradrenaline in the brain in patients with PTSD are too high. And I was at a conference some years ago where I was presenting this theory. We just presented this theory. It was a theory and it was in search of data. And it turns out at the same conference, it was one of those incredible moments. You get hairs on the back of your neck.

• 1:26:34Dr. Matthew Walker?

  There was a psychiatrist from Puget Sound, which is just outside of Seattle on the west coast of America. And he had been treating his war veterans in the Veterans Administration with a blood pressure medication called Prazosin. Now, it turns out that Prazosin, it's a generic drug because it's the Veterans Administration, so it's cheap and it crosses the blood-brain barrier. When Prazosin gets into the brain, one of the things that it does is shut down levels of noradrenaline. Why was this interesting? What he was perplexed by is that he was saying, "I'm giving this blood pressure medication to my war veterans with PTSD. It's not helping too much with their blood pressure, but they're all coming back saying,

• 1:27:15Dr. Matthew Walker?

  'All of those repetitive nightmares, they're starting to go away and I'm sleeping better and I'm feeling better.'" What he had done was inadvertently treated their high levels of noradrenaline, which were preventing the brain from kind of stop dropping those levels of noradrenaline down and processing the emotion from the memory. It was too high in those PTSD patients, but by treating them with this drug, he'd inadvertently brought the levels of noradrenaline down during REM sleep. And then it ultimately became one of the only prescribed medications in the Veterans Administration for repetitive nightmares. Because why? The brain had finally got down into a quote-unquote "safe chemical state" because noradrenaline

• 1:27:59Dr. Matthew Walker?

  was too high, but he treated them with this drug. So he had data that was in search of a theory. I had a theory that was in search of clinical data. And so I raced to him after he gave his presentation. I said, "I think I know why you're finding what you're finding." I flew him down to Berkeley. We spent all day together, went out for dinner together. And as I said, ultimately, he went on to do clinical trials. And it's not a cure-all for everyone, by the way. It doesn't work for everyone. And I would say that there is now a better treatment for nightmares if you're suffering from nightmares. And it's called image rehearsal therapy, or I R T.

• 1:28:40Dr. Matthew Walker?

  And it works through an incredible mechanism of memory that we actually had discovered about, gosh, 20 years ago now, called memory reconsolidation. So when you learn information, it would be, oh, let's take a Word document. Wouldn't it be daft if you opened up a Word document, you started typing in, you know, all this information, you hit save, and then you come back tomorrow and you double-click on the document, and Word has shut you out, you can't edit the document. That's a really bad information storage system. It's a bad idea. Your human memories are just like this. You form new memories, then you sleep and you save them. But when you come back and you reactivate that memory, when you recall a memory, you

• 1:29:25Dr. Matthew Walker?

  bring it back into this opened-up state. It's like double-clicking on the memory, and the memory becomes fragile and malleable once again, so you can update and edit that memory. And then the next night, you re-save it. It's called reconsolidation. So the first night, I save it, that's consolidation. Then I reactivate it, I modify it, and then the next night, I reconsolidate it. So coming back to nightmares, it turns out that you can do this with trauma patients who have nightmares caused by trauma. For example, let's say that you got into a horrific road accident, and you went through, your brakes failed, you went through the red light, you got T-boned, it was just traumatic, it was all traumatic. And what you do with the therapist, because you're having these repetitive nightmares

• 1:30:10Dr. Matthew Walker?

  of reliving that same car crash every night, you work with them and you tell them the dream, you recall the dream actively, out loud. But then, working with a therapist, what you do is you modify the outcome. So instead of me saying the brakes failed, now in the new scenario with your therapist, you say, well, you look down and there's a manual handbrake in the car. So you realize that you can actually just gradually start applying the handbrake, and you bring the car to a safe halt, and you go to the side of the road, and there's no accident. And what you're doing is, you're reopening back up that trauma memory, and you're rewriting the narrative. And then you sleep and you update that memory.

• 1:30:52Dr. Matthew Walker?

  And by recalling and rewriting the memory each and every waking day, you end up dissipating the severity of your trauma nightmare every single night. And it's called image rehearsal therapy for nightmares. It's incredibly powerful, probably more powerful than the presesin drug that I spoke about.

• 1:31:12Steven Bartlett?

  And I'm guessing people don't sleep and also have nightmares for a variety of reasons relating to trauma generally.

• 1:31:18Dr. Matthew Walker?

  Ah, it's a good question, perhaps, which is, in some ways, what's the difference between a bad dream and a nightmare? Because all of us will have bad dreams. Bad dreams are usually things that happen infrequently. Maybe you have them once every month, every couple of months.

• 1:31:35Steven Bartlett?

  Yeah.

• 1:31:35Dr. Matthew Walker?

  The definition of nightmare disorder is that you have to have these dreams frequently, maybe at least twice a week. They have to wake you up out of your sleep and you have vivid recall. Plus, it has to cause you some kind of daytime distress where you're not feeling good about the day. It's causing you mental anguish. And furthermore, if it starts to lead to hopelessness or a sense that your life is not worth living, you absolutely need to go and see someone. And here's what we've discovered about nightmares. Short sleep duration, not getting enough sleep, sleeping less than six hours,

• 1:32:17Dr. Matthew Walker?

  predicts by about a hundred to a hundred and fifty percent higher percentage chance of you having suicidal thoughts, attempting suicide, or tragically suicide completion. That's bad sleep. It turns out that nightmares, so if short sleep has a hundred and fifty percent higher likelihood of suicidality.

• 1:32:42Dr. Matthew Walker?

  Having nightmares has an eight hundred percent higher likelihood of suicidal tendencies associated with it. Now, we don't think that nightmares are causing suicidal tendencies. That's not what we believe. We believe, however, nightmares much more than disrupted sleep. Nightmares seem to be the canary in the coal mine. Nightmares are this distress beacon that leaks from our electrical static of sleep at night. And it is incredibly sensitive to your suicidal tendencies, your suicidal attempts, and as I said, suicide completion as well. Nightmares are a biomarker. If you are having distressing nightmares that are waking you up,

• 1:33:27Dr. Matthew Walker?

  you need to go and speak to someone about it. It's absolutely paramount because there are good, effective ways that you can dissipate those nightmares.

• 1:33:36Steven Bartlett?

  I was trying to understand whether it's a malfunction or it's a signal. I guess it might be both.

• 1:33:41Dr. Matthew Walker?

  It's a very good question, which is, is it adaptive? Or is it maladaptive? Is it a good thing to have a nightmare? Or is it a bad thing to have a nightmare? We don't quite have the answer to that. But let me come back to, I told you there were two functions of dream sleep. And we're still in the first one, which is emotional first aid. And it turns out that your thinking is incredibly astute. We believe that at least normative dreams, not nightmares. Nightmares may be the system failing, just as I spoke about in PTSD with repetitive nightmares. And in fact, repetitive nightmares are so consistent in PTSD that you can't receive a diagnosis of PTSD without having repetitive nightmares. That's how sort of diagnostic they are.

• 1:34:25Dr. Matthew Walker?

  But dreaming, normative dreaming, even if they're bad dreams, is beneficial. How can I make that claim? There was a study done by a late sleep scientist, a woman called Rosalyn Cartwright. And she was studying people who'd gone through a difficult period, let's say bereavement or a very bitter divorce. And they had become depressed because of that experience. And around the time of the experience, she was seeing them as a therapist, and she was having them do dream recall. So she was having them create dream diaries every single night. And then she tracked these patients for a year. And it turned out about roughly half of them by 12 months later had remitted from their depression. They'd got better. They'd got past their depression.

• 1:35:09Dr. Matthew Walker?

  The other half were still depressed. So then she took that data and she went back with those two groups. And she said, is there anything different about their dreams? And it turned out that there was. Both of those groups of people, whether they cut free of their depression or they stayed in their depression, both of them were dreaming at the time. Both of them were having REM sleep. Both of them were dreaming. What was the difference then? Those individuals that went on to gain remission to their depression and get better, those people were dreaming of the events itself at the time that they were happening. Whereas those other people who didn't go on to gain clinical remission, they were dreaming. They just weren't dreaming of the experiences itself.

• 1:35:54Dr. Matthew Walker?

  In other words, it's not just sufficient to have REM sleep. It's not just sufficient to have REM sleep and be dreaming. You need to be dreaming of the difficult, painful experience that you're going through to gain that clinical resolution.

• 1:36:09Steven Bartlett?

  Damn, so if I have something going on in my life, I need to think about it before I go to bed?

• 1:36:13Dr. Matthew Walker?

  Yes and no. What you have to realize is that it's taken us, depending on who you believe, 3.4 million years of evolution to develop this thing called hominid sleep and dreaming and REM sleep. I think that evolutionary millions of years probably understands what the correct blueprint playlist of dream experience is and should be for me at night. And therefore, I don't need to worry about it. I shouldn't try to force anything. That's the first function of dream sleep, is that it's emotional first aid. And we've got good data for that. But there's a second, completely independent benefit of dreaming.

• 1:36:58Dr. Matthew Walker?

  Dreaming is a form of informational alchemy. Dreaming is creativity. Now, I told you that during deep non-REM sleep, we take new memories that we've learned and we fixate them like amber sort of setting a fossil in. And we do that during deep sleep. That saves the individual pieces of the new stuff. Then comes along REM sleep, which happens after deep sleep. And the second phase of memory processing happens. That's where REM sleep starts to fuse all of the things that you've recently been learning with this entire back catalogue of information. And so you wake up with a revised mind wide web of associations that is capable of divining solutions

• 1:37:41Dr. Matthew Walker?

  to previously impenetrable problems. So, you know, it's almost, it's like group therapy for memories that REM sleep gathers in all of the information that you've learned during the day and everyone gets a name badge. But unlike the waking logical connections that you make already, REM sleep is like a Google search gone wrong, that you insert, let's say, diary of a CEO, and it takes you to page 20. This is dream sleep. And it's about some field hockey game in Utah. And you think, hang on a second, but how on earth is that? Well, there was someone who had, you know, they'd found a diary that had been lost, you know, a long time ago. And the guy who'd found it was a famous CEO in the town of this sort of, you know, Utah as he was watching.

• 1:38:26Dr. Matthew Walker?

  So it's a distant, non-obvious connection. But it turns out that that's what dreaming is all about. It's almost as though we go to sleep with the pieces of the jigsaw. But by way of dreaming, we wake up with the puzzle complete. And when you start to fuse things that should not normally go together, but when they do, every now and again, cause a marked advance in evolutionary fitness, that is the biological basis of creativity. It's the reason that no one has ever told you, look, Stephen, you should stay awake on a problem. They don't, they tell you to sleep on a problem. And in every language that I've inquired about to date, from, you know, from French to Swahili,

• 1:39:10Dr. Matthew Walker?

  that term, sleeping on a problem or something like it exists. My point being is the benefit, the creative benefit of sleep transcends cultural boundaries. It's a common experience of Homo sapiens.

• 1:39:23Steven Bartlett?

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• 1:40:08Steven Bartlett?

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• 1:40:52Steven Bartlett?

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• 1:41:18Steven Bartlett?

  What is the most important thing we haven't talked about as it relates to the personas of those people that are probably listening right now and for the reasons why they might have clicked, you know, that they're probably looking, again, we have the optimizers, we have those that have bad sleep habits, and then we have those that have real sleep disorders. What is the most important thing we haven't talked about that we should have talked about for them?

• 1:41:36Dr. Matthew Walker?

  It may be the dystopian future.

• 1:41:39Steven Bartlett?

  Let's talk about the dystopian future.

• 1:41:41Dr. Matthew Walker?

  What is a podcast if it does not contain, at least in this day and age, a dystopian future?

• 1:41:47Steven Bartlett?

  What is the dystopian future?

• 1:41:49Dr. Matthew Walker?

  Probably the most spectacular discovery that has happened since you and I last spoke is the discovery of what we call the genetic short sleepers. These are individuals who, by way of a genetic mutation, can survive on as little as 6.25 hours of sleep, in other words, six hours and 15 minutes of sleep, and they show zero impairment in their brain or their body. They can do just fine on six hours of sleep.

• 1:42:18Steven Bartlett?

  I know where this is going.

• 1:42:20Dr. Matthew Walker?

  And we have four genes that we've identified now. The first two genes, the first one identified was called the DEC2 gene, D E C two gene. The second was called the A D R B one gene, which I granted, I know it sounds like the next Radiohead album, but it's not the next Radiohead album. And these genes allow these individuals to get away with an amount of sleep that normally would cause predictive disease and sickness, just as we've spoken about. So at this point, probably some people listening are thinking, I think I'm one of those people. Just to put it in context, the probability that you will be struck by lightning in your lifetime is 0.0064.

• 1:43:09Dr. Matthew Walker?

  Highly unlikely. The chances of you having the ADRB1 gene is 0.004.

• 1:43:16Steven Bartlett?

  And the ADBR1 gene is the short sleeper gene?

• 1:43:19Dr. Matthew Walker?

  It's one of the short sleeping genes. So in other words, you are statistically more likely to be struck by lightning in your lifetime than you are to have that short sleeping gene. So the probability is low. By the way, why is this the case? Why do they get away with this? And we've discovered now by using sort of genetic manipulations, we understand why. First thing is that they have a much stronger wake drive during the day. So you and I and all the rest of our mere mortals will have these kind of like oscillations in our consciousness throughout the day where we'll have dips, where we feel a bit sleepy and we're dragging and then we'll kind of get... They don't have that. They have... It's like a light switch, like a dimmer switch.

• 1:44:00Dr. Matthew Walker?

  You and I, we may sort of go up to like 80% brightness when we're awake. And then sometimes we'll flicker and then we'll go down and we'll have pretty solid sleep, maybe sort of, you know, down to 20%, but the lights are not quite off, you know? Where sleep is good, but not amazing. These people have an all or nothing phenomenon. They are all 100% bright light throughout the day. And then, and they can maintain 17, 18 hours of wakefulness, no problem. And then when they sleep, they sleep hard. They have much more efficient sleep. Remember we spoke about sleep efficiency and I want it 85% or above. Almost all of their time at night spent in solid, stable, sound sleep.

• 1:44:44Dr. Matthew Walker?

  And the depth of their sleep they have is greater. So they're awake more throughout the day. They build up a stronger wakefulness drive, which is called adenosine, which means that when they sleep, they sleep harder throughout the night, which means that they can then be awake for more powerful stints during the day. Second, they don't suffer from jet lag.

• 1:45:03Steven Bartlett?

  What the f... What do you mean they don't suffer from jet lag?

• 1:45:06Dr. Matthew Walker?

  Because of their strength of wakefulness drive, when they are circadian misaligned, it's as though they haven't travelled between time zones. They can just stay awake. They have a strong drive for wakefulness.

• 1:45:17Steven Bartlett?

  Who are these people?

• 1:45:19Dr. Matthew Walker?

  They are these genetic, short, sleepers.

• 1:45:22Steven Bartlett?

  And do they pass these genes on to their children?

• 1:45:23Dr. Matthew Walker?

  Yes, they do.

• 1:45:24Steven Bartlett?

  And so their children have the same?

• 1:45:25Dr. Matthew Walker?

  They're heritable.

• 1:45:27Steven Bartlett?

  Can I have?

• 1:45:28Dr. Matthew Walker?

  Well, firstly, let's take a step back before I get to the dystopian. This tells us something above and beyond biological fascination. It says there is a profound statement in evolution. Mother Nature has figured out a way genetically to zip file sleep.

• 1:45:46Steven Bartlett?

  Zip file?

• 1:45:47Dr. Matthew Walker?

  You can compress eight down into six. You know, on your computer, you can get a collection of files, you group them all together, and then you say, "compress these files", and you compress them and you zip them into a single file, and it's dense, it's packed, and it takes up less amount of volume.

• 1:46:05Steven Bartlett?

  Do they have the same life expectancy?

• 1:46:07Dr. Matthew Walker?

  They seem to, from everything we can tell. So somewhere along the way, through genetics, evolution has figured out how to go from eight and compress it down to six. Where's the dystopia? Well, we've all heard of CRISPR, which is this genetic editing manipulation tool that a lab next door to mine at UC Berkeley discovered, Jennifer Downer. She won a Nobel Prize for it. Is there some future? And I hope not. Is there some future where we start to genetically engineer people from a need of seven to nine hours down to a need of six? Imagine the reduction in healthcare burden cost, because right now, the burden of insufficient sleep is vast.

• 1:46:51Dr. Matthew Walker?

  Insufficient sleep will cost most nations about 2% of their GDP. Here in America, it's $411 billion of cost caused by insufficient sleep. In the United Kingdom, it's about $40 billion. In Japan, it's $50 billion. Solve the sleep loss epidemic, which I have been trying to do by saying, you know, "sleep enough", and you could, you know, cause massive financial disruption, in the good way. But here, if you start to genetically engineer people, could you reduce the burden that is caused by people currently who need seven to nine? And take that burden away because they no longer need seven to nine.

• 1:47:29Steven Bartlett?

  Why did you say I hope not?

• 1:47:31Dr. Matthew Walker?

  Well, I hope not because I think here's the following that happens. It's not that I'm against that idea. I would love for the burden of disease and sickness to be reduced and people not to suffer from that. And if I could find a way to do it genetically, I would. And you could think about people arguing, well, imagine the productivity benefits. I mean, huge upsides of that. You know, people are being more productive and they're probably spending more. So from a capitalistic society, it's the perfect, it's the ad man's dream. Because when you're asleep, it's antithetical to a capitalistic society. Why? Because you're neither producing nor consuming. That's very cynical and I don't buy into that, but nevertheless. So all of these things would be markedly better, would they not be? If we genetically engineered this way, why do I fear it?

• 1:48:14Dr. Matthew Walker?

  I know for a fact that as soon as six becomes the new eight, everyone starts sleeping four. And now I'm just back into the same battle again. Because six is the minimum that you need. And they say, well, if that's the minimum, then I'll sleep four. And when I find the next gene that allows you to get away with four hours of sleep, then they say, well, that's great. So then I can go down to two. And it's a form of almost this sleep currency, you know, inflation that I'm always fighting a battle. And at some point, I'll always be on the wrong side of that battle.

• 1:48:48Steven Bartlett?

  Crazy. These people with this gene can thrive on four to six hours sleep without any negative effects that most of us would experience.

• 1:48:58Dr. Matthew Walker?

  Correct.

• 1:48:58Steven Bartlett?

  Very jealous.

• 1:49:00Dr. Matthew Walker?

  So, you know, what is going on there? And what we're seeing is this, this incredible density of sleep and this epic drive for wakefulness. They are more efficient sleepers. They can get done what you and I take eight hours to do. They can do it in six.

• 1:49:16Steven Bartlett?

  And I guess you, is there a way to easily test this? I guess going to a lab and get.

• 1:49:19Dr. Matthew Walker?

  Yeah, so if you've ever done, you know, I think, you know, all of those genetic testing kits out there where and a lot of them will allow you to download your raw data. All you need to do is download your raw data. And then there's a company, I think it's called Prometheus. Again, I have no affiliation with them. I don't know how valid they are. But then you upload your raw genetic data into their model. And then it will list and it will rip it apart. So normally those genetic services, they give you a nice PDF and it's kind of like maybe 15 pages of all of the main stuff. And it's, this Prometheus is kind of like the, you know, the. Old school, kind of scientist nerdy, they will just give you this kind of raw, just kind of janky, you know, fifty page report.

• 1:50:03Dr. Matthew Walker?

  The interface is terrible, but you can go in there and you can search to see, you know, what form of the DEC two gene do I have? Or what form of the ADRB one gene do I have? And it will tell you, are you a genetic short sleeper? Or are you not? And you can find out.

• 1:50:20Steven Bartlett?

  I've been thinking a lot lately about about certain diet states as well, and whether they have an impact on sleep. We're talking about circadian rhythms there. I was thinking about fasting a lot. And also, I think me, myself and Jack, who are there in ketosis right now. I was wondering if you, when you think about brain performance and sleep and different sort of states, do you think much about fasting? Or about ketosis? Or?

• 1:50:42Dr. Matthew Walker?

  Yeah, it's a mixed bag. If you look at it, certainly what you eat will change how you sleep. But perhaps more powerfully is how you sleep dramatically changes how you eat and how you dispose of those calories and what happens inside of your body when you are underslept. But.

• 1:51:03Steven Bartlett?

  So I have lots of cravings when I've short slept.

• 1:51:06Dr. Matthew Walker?

  Yes, you have. And there's a reason why is firstly, two appetite hormones called leptin and ghrelin will go in opposite directions. So they sound like hobbits, I know. And I've got some Lord of the Rings thing here. But leptin is the signal that says to your brain, you're full.

• 1:51:22Steven Bartlett?

  Yeah.

• 1:51:23Dr. Matthew Walker?

  You're satiated, don't eat anymore. Ghrelin is the opposite. It kind of makes your tummy growl and it says you're hungry. You're not full, you need to eat more. When you are underslept, leptin, which says you're full, stop eating. That hormone is impaired, drops away. So you lose the I'm full signal. And worse still, the ghrelin signal, which says I'm hungry, that increases. And so now you have about a thirty to forty percent increased hunger drive. And the final part of this is that when you are underslept and taking on board calories, the way that you dispose of that energy is different.

• 1:52:04Dr. Matthew Walker?

  Your body has a higher predilection when you are sleep deprived to disposing of calories as fat rather than storing it, for example, as glycogen in the muscles.

• 1:52:16Steven Bartlett?

  Oh, so when I'm underslept, that's why you're more likely to get belly fat?

• 1:52:20Dr. Matthew Walker?

  Correct. And what's worse is that there was a great study where they looked at people who were dieting and either getting sufficient sleep or not getting sufficient sleep. What was fascinating is that both of those groups, whether you are well-slept or not well-slept, you both lost weight. In fact, you lost about the same amount of weight. So you'd think, okay, so that's fine. The problem was, if you looked at what you were losing, there was an issue. Those people who were dieting but not getting sufficient sleep, seventy percent of all the weight that they lost came from lean muscle mass and not fat. In other words, when you're not getting sufficient sleep, you keep what you want to lose, which

• 1:53:03Dr. Matthew Walker?

  is fat, and you lose what you want to keep, which is muscle.

• 1:53:08Steven Bartlett?

  Oh, gosh. Damn, it's important, isn't it, this sleep stuff?

• 1:53:12Dr. Matthew Walker?

  But coming back to ketosis, by the way, I would say when people go into a fasted state, usually what we see is that their sleep gets shorter. And they'll say, I sleep almost more efficiently. I'll sleep for maybe just four or five hours, but I feel more alert and more awake. Now, some of that has to do with the ketosis. When you are calorically deprived, the brain starts to realize that something is wrong because you are lacking calories, you're going into starvation. So it drives on a chemical called orexin. Erexin is a wake promoting chemical and it forces your brain to release much more of this wakefulness chemical called orexin.

• 1:53:55Dr. Matthew Walker?

  So now, when you're fasting, it's easier to stay awake for longer and your brain will deliberately stop you from sleeping as much. It's not because it wants you to sleep less, it's because the only time during our evolutionary past that we unexperienced short sleep was when we were in a caloric deficit. And the reason comes back again to this idea that you have to stay awake longer because you're not finding food. Now, your brain doesn't know you've deliberately decided to fast, which is a good thing in lots of ways. But that's one of the reasons that when people are fasting, they'll say, my sleep goes to heck in a handbasket, you know.

• 1:54:35Steven Bartlett?

  Mine goes really, really short. So when I'm in ketosis now and I'm like in, on my way in, and my sleep will reduce to about five, five, six hours, my whoop scores plummet.

• 1:54:44Dr. Matthew Walker?

  Yeah.

• 1:54:45Steven Bartlett?

  Until I kind of come out the other end, which might take a couple of weeks, and then my sleep scores seem to stabilize again. But that initial transition period, it looks like it's having a physiological shock.

• 1:54:55Dr. Matthew Walker?

  It is, and the shock is this chemical orexin, which is this wake promoting chemical, which will force you to stay awake in a very solid fashion. By the way, case in point, people with narcolepsy, this sleep disorder where they inadvertently and uncontrollably fall asleep during the day, they have the opposite. I'm just telling, I was just telling you that when you are fasting, your brain dumps out this chemical orexin to force you awake and you're wide awake. People with narcolepsy, when we've studied their brains, they have a deficiency of this brain chemical orexin, so they can't stay awake in a stable fashion. They have the opposite of your fasting problem. You're wide awake because you've got too much orexin.

• 1:55:35Dr. Matthew Walker?

  They've got too little orexin and they, therefore, they can't sustain stable wakefulness during the day, so they're constantly falling asleep. This story of orexin has led to the invention of the first new class of sleeping medication that I actually favor, and most people are not aware of it. It's a new class of, we're on to essentially Web 3.0 of sleep medication. Web 1.0 where the benzodiazepines, things like Xanax and Valium, not great for sleep.

• 1:56:05Dr. Matthew Walker?

  The second wave, the Web 2.0, those were things like Ambien, Lonestar, Sonata. Both of those drugs worked in a very similar way, where they go up to your cortex and they tickle a receptor called the GABA receptor, GABA, G-A-B-A, and it's the major neuroinhibitory transmitter of the brain. So when these drugs flood your brain, they just hit the red light and they stop neural firing of the cortex. Essentially, they sedate you. And sedation is not sleep. But when you take an Ambien, you mistake sedation for sleep. It's not quite the same. It's not naturalistic sleep. But after we realized by way of the story

• 1:56:48Dr. Matthew Walker?

  of narcolepsy, that narcolepsy patients, they don't have this chemical orexin, and they're falling asleep inappropriately during the day. Well, think about what insomnia is at night. Insomnia is almost the opposite of narcolepsy, which is that narcolepsy patients, they're falling asleep during the day when they want to be awake. Insomnia patients are awake at night when they want to be asleep. So what they realized is that what we can do, if this chemical orexin, this wakefulness volume button in the brain, is a problem in insomnia patients, what if we were to just develop a drug that doesn't sedate the

• 1:57:28Dr. Matthew Walker?

  cortex like Ambien? Instead, it goes down into the brainstem where the center for orexin is, and these new drugs, and they're called the DORAS drugs, D-O-R-A, small s. And to class of drugs, there are three FDA-approved, and I'll try and spell them out for you, they're called Suborexent, Lomberexent, and Daridorexent. Why my synapses are filled with things like those names, but there you go, the three FDA-approved drugs. And what they do is they act like a clever set of chemical fingers. They go down into the brainstem where this sort of orexin is being released, and they just dial down the volume on wakefulness, and then they take a step back and they allow the antithesis of wakefulness

• 1:58:13Dr. Matthew Walker?

  to come in its place, which is this thing called naturalistic sleep. Now, if you look at that, those clinical data, they absolutely make you sleep for, not necessarily a longer period of time, but you're awake a lot less. So you've got nice sleep efficiency, more continuity. But I, as a scientist, could be very skeptical, and I could come along and say, okay, so this new drug, it increases your total sleep time, improves your sleep efficiency. But I have four words, yes, and so what? Just because I've added sleep to your night, how do I know that that's functional sleep? How do I know that that's useful sleep? Couldn't it just be like junk DNA? It could

• 1:58:56Dr. Matthew Walker?

  be just junk sleep? Well, they did a study where they looked at what we call the glymphatic system in your brain. There's a cleansing system in your brain that kicks into high gear during deep non-REM sleep, and it flushes the brain of all of the metabolic toxins, two of which are things called beta-amyloid and tau protein, which are the culprits of Alzheimer's. And that's why we know that sleep is so important, because at night, it's a good night to sleep clean. It's a power cleanse that washes away the Alzheimer's toxins. So they did a study. Heavens knows how they got these people to participate. But they brought them in, they were 50 years or older, and in the morning and the night

• 1:59:35Dr. Matthew Walker?

  before, they had a lumbar spinal puncture, and they siphoned off cerebrospinal fluid so they could measure how much of the metabolic detritus was in the brain before sleep and in the brain after sleep, including the metabolic waste product, sort of including beta-amyloid and tau protein. And they either had one of these drugs, the Dora's drugs, or they had a placebo. And fair enough, when they took this new class of medication, the Web 3.0, the Dora drug, their sleep got better. But what they also found is that not only did their sleep get better, but they had cleansed the brain the next morning

• 2:00:17Dr. Matthew Walker?

  of more beta amyloidin tau protein than the placebo group. In other words, it wasn't just epiphenomenal junk sleep. It was beneficial sleep. It was adaptive, useful sleep because that drug induced sleep had washed away more of the Alzheimer's proteins. And it was the first demonstration, and they've now replicated it in animal models, that this is a sleeping pill that isn't disadvantageous, which we know to be the case for things like Ambien. In fact, Ambien, there was a recent study that showed that it decreases the cleansing pulsing fluid by about thirty to forty percent at night. But this is a new class of medications that does the opposite.

• 2:00:58Steven Bartlett?

  And this is new?

• 2:00:59Dr. Matthew Walker?

  And this is new. The DORAS drugs, D O R A S. The problem is that a lot of insurance companies here in the United States currently do not reimburse, some do. And I believe that it's some of these of the three DORAS drugs, not all of them are available in Europe or in the UK. And because they're just so expensive. And if you pay out of pocket, it can be up to $400 a month for these medications. Now, some insomnia patients, when I go to them and say, at the end of a shockingly bad month of sleep, if I went to them and said, look, if you gave me $400 now, could I, I could wave a magic wand and eradicate all of that bad sleep over the previous month. Would you like to give me $400? Most of them would say, absolutely, take my money.

• 2:01:42Dr. Matthew Walker?

  But still, people are being priced out at this stage. But the DORAS drugs, please look into them if you're struggling with insomnia as well as CBTI.

• 2:01:50Steven Bartlett?

  I didn't realize there was so much new science and research that had been discovered on how to sleep well, what's going on in the brain, and also some of the lifestyle factors that have made sleeping so hard for so many people. And with that in mind, I want to do something that I've never done before, which is a world first for the Diary of a CEO, is I'm going to put a link below because I think this is a particular episode where if you share this conversation with some of your friends who particularly struggle with sleep or sleep optimizers or who have sleep disorders, they'll get a ton of benefit from it. So what I'm going to do is in the description of wherever you're listening to this podcast right now, there is a link. And if you click on that link, you'll see that you've got your own personalized link to share this episode. And those of you that share this episode,

• 2:02:34Steven Bartlett?

  whether it's on your story on social media or in a WhatsApp group or wherever, on email with your friends. You will collect points for every person that listens and I will reward those. And you'll see as you click on the link who have shared it the most. In part, I say this because so many of you come up to me in the street and they came up to me after our last conversation. And they said, um, that conversation you did with Matt Walker was so amazing. I sent it to my aunt and she now da da da, she did this and she's changed this and blah, blah, blah, blah. And she's now sleeping well. And then all the downstream impacts of that have been profound. So I'm going to create this little system to encourage all of you to share it with someone that is struggling at the moment with sleep. Cause I do believe, I do believe that sleep is upstream from so many of the downstream symptoms that ruin our lives.

• 2:03:17Steven Bartlett?

  Whether it's relationship issues, whether it's libido issues, or whether it's creativity issues. I mean, I was reading through your work and I saw your conversation with Rogan not so long ago, where you talked about the fact that a sleep deprived person has their genes fundamentally working differently. You talked about 700 genes working differently.

• 2:03:33Dr. Matthew Walker?

  Yeah, 711 genes are distorted in their activity caused by a lack of sleep. Some genes that are over expressed that are related to cardiovascular disease or stress or inflammation. And other genes that are impaired, which are associated with your immune system. So you become immune deficient.

• 2:03:50Steven Bartlett?

  And it can be a downward compounding spiral. If you're such a person that's really continually struggling, struggling with sleep and building up some of that sleep debt. So that link is below, check it out. And we have a closing tradition on this podcast where the last guest leaves a question for the next. The question left for you is, what did success bring you that you never could have dreamed of?

• 2:04:12Dr. Matthew Walker?

  It brought me two things. One beneficial, one less so. Beneficial is that I have now the chance and have gifted the chance to

• 2:04:27Dr. Matthew Walker?

  fly around the world and try to speak the word of sleep because the physiology of it is so silent. And I used to lament why me? Because there are so many other much better sleep scientists in the world than me. And a friend, after I was saying, like, I don't understand why me, an imposter syndrome. And he just told me to shut up and accept that it's you. And instead asked the question, what are you going to do with it? And I changed how I embrace that. So I've been so fortunate that my life after publishing the book that you're holding. Change forever and almost all for the better. And I'm so fortunate.

• 2:05:09Dr. Matthew Walker?

  I have lived a life of such fortune by way of the sleep mission. I would say, though, that there is. Also, and I suspect you may experience some of this too. When you raise your head above the public parapet, don't be surprised if shots are fired. And if you're someone who has even the vaguest hint of insecurity, comments will do you a lovely disservice. And so I think there's a degree of kind of vulnerability and insecurity that you can develop by way of becoming someone who is in the eye of the public.

• 2:05:54Dr. Matthew Walker?

  That had I not been in the eye of the public, I probably wouldn't have been, you know, as self-conscious about whether it's, you know, your intellect or your voice or your, you know, disastrous, you know, boy band haircut, whatever it is. I would say that's the only slight downside. Overall, I am the most fortunate human that I know. I am so gifted by way of this thing called sleep. It's a love affair that's lasted me almost 25 years. And I believe it's the most beguiling topic in all of science. And it has treated me so well.

• 2:06:29Steven Bartlett?

  You happy?

• 2:06:32Dr. Matthew Walker?

  More than you could imagine. At this moment in my life, I am the happiest I've been.

• 2:06:39Steven Bartlett?

  Why?

• 2:06:40Dr. Matthew Walker?

  I have a piece that I found in life for reasons that I can share or not share and.

• 2:06:48Steven Bartlett?

  Go ahead and share them. I'd love some peace in my life.

• 2:06:50Dr. Matthew Walker?

  You know, I found my person and and she is, she appeared like lightning from a clear blue sky. Never saw her coming. And it's interesting that I've never been able to be more myself, even with myself than I have with her. Every day she makes me want to be a better person. And.

• 2:07:27Dr. Matthew Walker?

  I have found peace that I have never had before.

• 2:07:31Steven Bartlett?

  That you've never had before?

• 2:07:33Dr. Matthew Walker?

  No.

• 2:07:35Steven Bartlett?

  Did you have peace last time we spoke?

• 2:07:37Dr. Matthew Walker?

  I wouldn't say I was without peace. I didn't know this type of peace.

• 2:07:44Dr. Matthew Walker?

  And I never believed in this notion of the one, you know, I was a scientist, I'm a hard-nosed, empirical kind of guy, and I just did not imagine it would be such. I didn't think there was such a one. I would have told you if you'd told me that two years ago, you'd given me your love story of certainty, I would have thought you're misguided and that, you know, you just need to put down whatever substances you're using because you're delusional, because there isn't such a thing.

• 2:08:20Dr. Matthew Walker?

  She's a gift.

• 2:08:23Dr. Matthew Walker?

  And I hope I never take her for granted. I doubt it. There's an incredibly sad story

• 2:08:30Dr. Matthew Walker?

  of a gentleman called Clive Wehring. And Clive is a famous individual in the neuroscience world. And Clive was the man who the movie Memento was based on, which is a movie where a man has brain damage and he has profound amnesia. And from that moment forward, he can never make any new memories whatsoever. He's densely amnesic. And he was a real-life individual. He contracted a virus that destroyed his memory centers. And from that point forward, he could no longer make any new memories. And he lived in just two or three seconds of time. And that spotlight of consciousness just moved forward in time.

• 2:09:12Dr. Matthew Walker?

  He had no recollection of the past. He had no anticipation of the future. And the only thing, the only person that he remembered and he would recognize is his wife. So he could have spent this whole three hours speaking to you, and then you would walk out the room for five minutes and you would walk back in and you'd say, hi Clive, nice to meet you. And he'd say, hi, what's your name? Had no recollection. The only person that he remembered was his wife. But the problem was, he never remembered how long it's been since he last saw his wife. And so every time that she would walk into the room after being out of it for five minutes, he would jump out of his chair and he had this incredible elation. And he would run and he would hug her and kiss her.

• 2:09:57Dr. Matthew Walker?

  And I think sometimes we take our partners for granted. And the only time we realise how precious they are is when they're gone.

• 2:10:06Dr. Matthew Walker?

  And I often think about that, that complacency can be one of the greatest negative forces in a relationship. And I always think about Clive Wearing, even on the days where I'm having a bad day or I'm in a bad mood and I'm not myself or I just don't want to be around someone. I always try to remember his reaction. And when my wife walks back in from work or I see her, you know, first thing, I try to remember how his reaction was and how I truly feel at the time, despite the blanket of negative stress, trying to drown that feeling out.

• 2:10:45Steven Bartlett?

  It's a beautiful thing. I think about that a lot as well.

• 2:10:47Dr. Matthew Walker?

  In what way?

• 2:10:48Steven Bartlett?

  Just the part of, I'm way more cognizant now on a frequent basis, almost on a weekly basis, of how I'm going to feel when my time is up as it relates to my romantic relationship. Like, I think even like mid-argument, I will now think, and then this actually happened like a couple of days ago. It wasn't really an argument, we were just disagreeing about something. I literally said mid dispute that we were having, I said, we're gonna regret this so much. And what I meant was, when that phone call rings and someone gives me bad news that either I'm going or you're going, I'm gonna regret that this thirty minutes was wasted doing this.

• 2:11:25Dr. Matthew Walker?

  Yeah.

• 2:11:26Steven Bartlett?

  I'm really gonna regret it.

• 2:11:27Dr. Matthew Walker?

  How much would you give to have that thirty minutes?

• 2:11:29Steven Bartlett?

  Exactly.

• 2:11:29Dr. Matthew Walker?

  Everything.

• 2:11:30Steven Bartlett?

  You know, we're fucking arguing about, I don't know, some chocolate, whatever it might be, some trivial thing. It's actually really helped me because in the midst of those storms, thinking through to that moment when you get that phone call and like you're ill or I'm ill and we're not gonna be around much longer. It liberates you from the pettiness that a sense of immortality can create. And that pettiness results in the complacency that you're describing that like, I took you for granted.

• 2:11:57Dr. Matthew Walker?

  Yeah.

• 2:11:57Steven Bartlett?

  So it's a nice little mechanism now for me to go, is this an important thing? Is this really important? And I have to provide nuance there, which is, this doesn't mean don't address things.

• 2:12:07Dr. Matthew Walker?

  Correct. Yeah, I was just about to say, conflict is critical. You've got to fight well.

• 2:12:12Steven Bartlett?

  But let it be me versus you and the problem, like me and you versus the problem versus me just going at you.

• 2:12:17Dr. Matthew Walker?

  Yes, you have to be fighting for each other, not fighting against each other.

• 2:12:22Steven Bartlett?

  Yeah, exactly.

• 2:12:23Dr. Matthew Walker?

  And that you have to try to then, in that context of Clive Wearing, don't shy away from conflict if you need to have the conversation. Often it's like the gym, if you do it well, you, even on the days when you kind of go into the gym, you think, I don't want to do this, or I just don't feel good. You always come out feeling better than you did before. And with conflict, if you do it well, you typically, it may not be the hour after or even the day after. But if you do it well, you typically are better as a couple after than you were before the conflict, as long as you do it well. So I'm not saying don't have conflict. What I'm saying is Clive Wearing's story to me of how he loved his wife

• 2:13:08Dr. Matthew Walker?

  with an intent that I'd never experienced before until I met my much better half, prevented me from resentment. Resentment is the barrier that will keep you from reparation and a future of, I think, equanimity. Because when you resent someone, it means that you haven't processed, you haven't moved forward. And resentment usually comes by way of, I think, a poor choice of things such as, did I win the argument? Did you win the argument? It's not about point scoring at least, and I've done that before. I've been guilty of all of that behaviour. But now with this person that I cherish most, you know, I think of his lessons. It's not that we don't have conflict, we do.

• 2:13:53Dr. Matthew Walker?

  It's just that I value the person far beyond the conflict afterwards. And I'll always want to reach out with an olive branch because it's not worth it. Just as you said, when that call comes. You know, I I think of that sometimes when I have a bad day. Let's say someone, you know, I come back to my car and my car has been rear-ended when it's been parked. Or, you know, I was coming here to fly out and we were four hours on the tarmac waiting. And there's a guy in front of me who's getting all agitated and giving the the ground staff all sorts of vitriol. And I was thinking, look, when you're on your deathbed, my good fellow,

• 2:14:36Dr. Matthew Walker?

  are you going to look back at this day and think, gosh, you know, I remember that one day when I was on that flight coming out to LA and it was four hours delayed? No, of course you're not. So if you're not stressing about it when you're dying, why are you stressing about it now? It's just not worth it.

• 2:14:55Steven Bartlett?

  Liv, thank you. Thank you so much. I mean, I can't thank you enough for the profound impact you've had on so many millions of people, being the the chief torchbearer of the subject of sleep and creating a movement around sleep, but also heightened awareness of ourselves and our struggles. And that is something that you'll never understand, like you'll never understand the full magnitude of the many millions of people you positively impacted. But, I mean, even though you'll never get to meet them all and you'll never get to hear all of their thank yous, they are very, very real people and they are, them themselves are these little ripples through the ocean where they're children and then the generations to come get to sleep better and enjoy their lives and live a happier, healthier life

• 2:15:37Steven Bartlett?

  because of the work that you do. So it's incredibly important work, Matthew, and I hope you long continue it and I long continue being the conduit of this very important information to people like me and my audience. Couldn't appreciate you more.

• 2:15:49Dr. Matthew Walker?

  Thank you so much for saying that. I can't lay claim to any such affirmations, but I would say that I stand on the shoulders of giants and that I am simply relaying all of the incredible work of all of my colleagues in the field and all of those who came before me. I'm just the mouthpiece and not a particularly good one at that. And for all of their work, it's really the appreciation that I give to them. So thank you for giving me the opportunity to say that.

• 2:16:19Steven Bartlett?

  Make sure you keep what I'm about to say to yourself. I'm inviting 10,000 of you to come even deeper into the diary of a CEO. Welcome to my inner circle. This is a brand new private community that I'm launching to the world. We have so many incredible things that happen that you are never shown. We have the briefs that are on my iPad when I'm recording the conversation. We have clips we've never released. We have behind the scenes conversations with the guests and also the episodes that we've never, ever released and so much more. In the circle, you'll have direct access to me. You can tell us what you want this show to be, who you want us to interview and the types of conversations you would love us to have. But remember for now, we're only inviting the first 10,000 people that join before it closes.

• 2:17:02Steven Bartlett?

  So if you want to join our private closed community, head to the link in the description below or go to D O A C circle.com. I will speak to you there.