Most replayed moment: Why sleep may be the key to heart health | Dr Nour Makarem

Today we’re talking about sleep. The more scientists study sleep, the clearer it becomes that it’s not just about resting our bodies - it’s much more than that. In fact, sleep is the foundation upon which a healthy diet, exercise, and overall wellbeing are all built upon. So what happens when that foundation is shaky? Recent research suggests that poor sleep quality may significantly increase your risk of heart disease and even heart attacks. Dr. Nour Makarem joins me to explore the powerful connection between sleep and heart health - and why both too little and too much sleep is a cause for concern. 🌱 Try our science-backed and tasty wholefood supplement Daily30 Get our brand-new app and Gut Health Test designed by world-leading gut health and nutrition scientists to build healthy eating habits 👉 Join ZOE Follow ZOE on Instagram. 📚Books by our ZOE Scientists The Food For Life Cookbook Every Body Should Know This by Dr Federica Amati Food For Life by Prof. Tim Spector Ferment by Prof. Tim Spector Good Mood Food (preorder) by Prof. Tim Spector Free resources from ZOE The Hormone Harmony Guide: Tuning Your Body’s Internal Orchestra Eating for Better Brain Health: Your brain-gut blueprint How to eat in 2026 - Discover ZOE’s 8 nutrition principles for long-term health Live Healthier: Top 10 Tips From ZOE Science & Nutrition Gut Guide - For a Healthier Microbiome in Weeks Better Breakfast Guide Have feedback or a topic you'd like us to cover? Let us know here. Episode transcripts are available here.

• 0:01Speaker 00

  Hello and welcome to Zoe Recap, where each week we find the best bits from one of our podcast episodes to help you improve your health.

• 0:10Speaker 00

  The more scientists study sleep, the clearer it becomes that it's not just about resting our bodies, it's much more than that. In fact, sleep is the foundation upon which a healthy diet, exercise and overall wellbeing are all built. So what happens when that foundation is shaky? Recent research suggests that poor sleep quality may significantly increase your risk of heart disease and even heart attacks. Dr. Noor McCarron joins me to explore the powerful connection between sleep and heart health, and why both too little and too much sleep is a cause for concern.

• 0:46Speaker 00

  What is heart disease?

• 0:48Speaker 01

  Basically, it's the narrowing of the arteries or the vessels in our body that supply blood to our heart, which of course is necessary for pumping blood to all of our organs so that we can function. And heart disease begins with the narrowing of those arteries, the decrease, or eventually even the abrupt stop to that supply of blood to our heart that can lead us to having a heart attack. And this is a process that happens for a lot of people over multiple decades of life before we get to that bad outcome of having a heart attack or a stroke in the case of the brain.

• 1:21Speaker 00

  I've also heard doctors often talk to me about high blood pressure. Has that got anything to do with this heart disease you're talking about?

• 1:29Speaker 01

  Yes, so high blood pressure, or what we call hypertension, is actually the number one cause of heart disease. It's the number one cause of dying from heart disease. Making sure that our blood pressure stays in the normal range is one of the best things that we can do to prevent developing cardiovascular disease or having a heart attack or a stroke.

• 1:47Speaker 00

  I'm actually really shocked to hear you say that high blood pressure is the number one cause of heart disease and heart attacks. Could you help me to understand what it is?

• 1:56Speaker 01

  Yes, blood pressure refers to the pressure on the walls of those blood vessels when our heart pumps and also when our heart is not pumping. So that's what those measures correspond to. We have an upper reading when we measure our blood pressure, which is the systolic blood pressure. And then we have this lower reading, which is the diastolic blood pressure. Both of them have been linked to future risk of heart disease and to heart disease outcomes. But generally, the measure on the top, the upper reading, is the one that I would say is more strongly related to our future risk of heart disease.

• 2:27Speaker 00

  And is there a simple way that you can explain to me, I guess, how this high blood pressure and this narrowing of arteries links to the thing I guess we're all scared of, which is a heart attack, which I think of as like my heart stops?

• 2:41Speaker 01

  You can think of it as a lot of pressure on the inner walls of the vessels. It creates damage and then that kind of facilitates the development of dysfunction in that wall, the deposition of fat in that wall that eventually leads to, that eventually accumulates and leads to that blockage before we get to the adverse outcome, which is the heart attack or the stroke.

• 3:02Speaker 00

  Advice, I'd like to discuss areas of your research because I know you've run some really interesting studies, particularly around sleep and circadian rhythms. I'd love for you to tell us about them and definitely make sure you explain what circadian rhythms are, as you do say.

• 3:18Speaker 01

  Sleep and circadian rhythms, those are two things that are very much intertwined and related, but they're also distinct. So let me start with sleep. So my work on sleep is focused more on what we call sleep health, which is kind of recognizing that sleep health is not just the absence of sleep disorders. A lot of people, when they think about sleep, they think about insomnia symptoms, so like symptoms of, which is difficulty falling asleep or staying asleep, or having sleep apnea, which is related to breathing during sleep and snoring. But sleep health is a distinct concept from having those sleep disorders. It refers to more adopting positive achievable sleep habits that can help us to optimize our health and that promote what we call healthy longevity, so having a long, healthy life.

• 4:04Speaker 01

  There's been many kinds of ways to define this concept of sleep health, but right now, I would say one of the most widely accepted ways or definitions of sleep health is a construct that is based on six things. So the first thing is sleep duration, or how much we sleep every night. And I would say that this is the most well-studied aspect of our sleep health. The second one, I would say, is sleep regularity. And this is something that people don't think about very much, but this refers to essentially how consistent are your sleep and wake time every day? Do you tend to go to bed at the same time each day and do you tend to wake up at the same time each day? And in general, what studies show is that people who have regular sleep schedules, so

• 4:47Speaker 01

  who tend to go to bed and wake up at a similar time each day, those individuals tend to be at a much lower risk of heart disease and a number of other chronic conditions. And studies are showing that people who have these irregular sleep patterns have double the risk of heart disease. It's very similar to what we see for things like established risk factors for heart disease, like diabetes and smoking and obesity. So it's kind of this new risk factor that's emerged and we're seeing that, wow, it really can substantially increase someone's risk of developing heart disease. There's a lot of studies now that show that even individuals who get enough sleep every night, if their sleep is irregular, they're still at higher risk of developing hypertension and cardio metabolic diseases.

• 5:30Speaker 00

  That's slightly terrifying. You're saying this is potentially as bad as smoking to have this really inconsistent sleep and wake time. Just one question before we move on, like how perfectly do you need to go to bed at 10pm every night in order for this to count as regularity versus what you're describing as irregular and this massive risk factor?

• 5:52Speaker 01

  People always ask that because no one can go to bed and wake up at exactly the same time every day, right? So I always say to people, as long as your sleep timing is not varying by more than 30 minutes to an hour each day, you should be okay. That's the practical advice that I would give. We start to see this substantial increase in risk for people whose sleep timing varies by an hour and a half, two hours, more than that each day. That's when you really start to see this kind of doubling in the risk of cardiovascular disease. So as long as you stick to this like 30 minute to an hour window, you can lower your risk.

• 6:27Speaker 00

  Point number three of sleep health?

• 6:29Speaker 01

  Point number three is the timing of sleep. When we sleep, we think that going to bed earlier is linked to lower risk of heart disease. Generally, if the midpoint of your sleep is earlier than 4am, that's considered to be protective. But I would say that this aspect is a little bit less studied than the other aspects when it comes to sleep health. The fourth point is sleep satisfaction. So this is just like the subjective experience of feeling like your sleep is restorative and feeling rested when you wake up. I know it sounds like a very subjective thing, you know, but it's actually been something that has been linked to heart disease even over and beyond things that we can measure objectively, like how much someone sleeps.

• 7:11Speaker 00

  I'm not totally surprised to hear that because I think one of the things that's been really interesting at Zoe, working with scientists here, looking at impacts of nutrition, is that they all started very skeptical about self-reported impacts around energy and mood. And what's interesting is that as we scaled up the studies, they've started to say, oh, no, we're completely convinced because these correlations are incredibly strong and these reports about mood, this is really real. But historically, they said they were sort of brought up that if you can't measure it with a blood test preferably, it's sort of not real science and like something self-reported about how you feel, that's not the thing that's done as a scientist.

• 7:55Speaker 00

  I don't know if any of that is true also in heart health?

• 7:58Speaker 01

  Yep, no, it's true. And I think, you know, it really underscores how much sleep is a sign of wellbeing, really. You're not always able to capture that from a biomarker or blood test. You know, that's something that extends beyond that. In a way, how well we sleep can be a marker of how stressed we are in our life. Two more, sleep efficiency, which is related to what we were just talking about. And this really refers to the amount of time in bed we are actually sleeping. And of course, having a higher sleep efficiency is a good thing. And the final one that is also related to all the metrics that I just discussed is daytime alertness. It doesn't seem like it's an aspect of sleep health because it's not referring to you when you're sleeping, but daytime alertness or daytime sleepiness is the opposite one,

• 8:44Speaker 01

  is also a marker of sleep health because obviously someone who is experiencing excessive daytime sleepiness, who is dozing off on the subway or at work, that's a marker of sleep that is not restorative and poor sleep health.

• 8:57Speaker 00

  And so when you look at all of these things together, you get like a sort of quantification of somebody's quality of their sleep?

• 9:04Speaker 01

  We look at them together because it's a way for us, first of all, to acknowledge that sleep is multidimensional, so it's not just one thing, it's not just how much we sleep, but also it allows us to measure kind of the gradient of healthy sleep. And when we look at them together, we find stronger associations with a number of chronic diseases. So in one study that we did, we looked at those individual metrics separately and there were many of them, you know, were linked to chronic diseases like heart disease and diabetes and obesity and hypertension, et cetera. But when we look at them together, we find much more strong, consistent associations with all of those chronic disease outcomes. So what that tells us is basically that the whole is greater than the sum of its parts,

• 9:46Speaker 01

  that when you improve your sleep as a whole, the health benefits are just going to be much more pronounced.

• 9:53Speaker 00

  You've talked a lot about sleep regularity, which I think to me sounds really is very new and you said it's really important. You know, you said that I can like double my risk of heart disease if my sleep regularity is really bad. What should I be doing in order to try and make my sleep regularity good?

• 10:12Speaker 01

  The easiest thing to get enough sleep and to make sure that your sleep is regular is to have a regular, a fixed sleep schedule. So making sure that you try to go to bed and wake up at a similar time each day and making sure that that schedule ensures that you get the seven to eight hours of sleep a night, because that's what the recommendations are, but not more than nine. Because both short sleep and long sleep have been linked to higher risk of heart disease. So for every hour of sleep less than the recommended seven to eight hours, you increase your risk of heart disease by 6%. That's an estimate. And then for every hour beyond the recommended seven to eight hours, so more, you have a 12% higher risk of cardiovascular disease.

• 10:54Speaker 01

  The second thing I would say is practicing good sleep hygiene, which refers to kind of the sleep environment and the habits that you can practice to put yourself in the best position to sleep well every night. I always say that good sleep starts in the day, it's not just at night. So in the daytime, making sure that you get plenty of sunshine, making sure that you're physically active in the daytime, that's all been linked to better sleep health at night. Making sure that you don't nap too much in the daytime because that can also disrupt your sleep. So if you do have a nap, make sure it's only 20 to 30 minutes, make sure it's earlier in the day, so before 3pm. Ideally, it would be midday, so in the midpoint of when you wake up and when you go to bed. Of course, avoiding stimulants before bedtime, so this includes nicotine and caffeine.

• 11:38Speaker 01

  The caffeine, you know, it's good to keep that just to the morning because if you drink coffee, let's say at noon, you still have caffeine in your system at midnight. Smoking similarly, I mean, you shouldn't smoke, but if you do smoke, try not to smoke within the two hours before bedtime. And similarly, alcohol too. Alcohol, actually, people think that it helps them sleep and it's true, it can help you fall asleep, but it impacts the quality of your sleep if you drink before bedtime. So again, trying to not drink very close to bedtime, within two hours at least, can help to make sure that the alcohol intake doesn't impact your sleep quality.

• 12:17Speaker 00

  That's it for this week's recap. If you're listening to this, you're already on your way to living healthier through better nutrition. And at Zoe, we're doing everything we can to help you on your way. So we've developed Daily 30, a delicious dietary supplement to add to your meals. Because we're Zoe, we ran a clinical trial testing Daily 30. The results were staggering. It's selling out in the UK and we're working hard to bring it to the US as soon as possible. Sign up to the waitlist at zoe.com/daily30.