The Economics of Sleep, Part 1 (Rebroadcast)

Could a lack of sleep help explain why some people get much sicker than others?

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

• 0:01Stephen J. Dubner?

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• 0:46Stephen J. Dubner?

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• 1:29Stephen J. Dubner?

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• 2:13Stephen J. Dubner?

  Hey, podcast listeners. It's Stephen Dubner. This week, we are bringing you an episode from our archives. It's called "The Economics of Sleep, Part One." And yes, that means that there is a part two, which you will hear next week. We thought it was time to replay these episodes because they are two of our most popular episodes ever. Now, why is that? I think it may be because as much as people tend to focus on nutrition and exercise as the vital inputs in maintaining the human machine, sleep often gets overlooked. So let's stop overlooking it, yeah? Hope you enjoy it, and I hope you learn as much about sleep as we did in making this episode.

• 3:02Stephen J. Dubner?

  We begin in Brownsville, Brooklyn, at the Brownsville Multi-Service Family Health Center.

• 3:08Speaker 01

  Good afternoon.

• 3:10Stephen J. Dubner?

  Graciela Flats, she goes by Grace, is a nurse and the clinic's director of nursing. She was born in Panama, moved to New York about 20 years ago.

• 3:20Speaker 01

  Something that I always say to everybody, I'm born to be a nurse. I love nursing, and I love my patient.

• 3:27Stephen J. Dubner?

  No matter how much you love your job, Brownsville is not necessarily the first neighborhood where most people would choose to work. It's got a lot of crime, a lot of unemployment, and not much money.

• 3:39Speaker 01

  You will be surprised to see the income that some people make here. Approximately between 60, 65% of our patients, they are under the poverty level.

• 3:50Stephen J. Dubner?

  The median household income in Brownsville is barely $27,000. About three-quarters of the residents are African-American. Grace Flats is also of African descent. She says that roughly 90% of the patients in her health clinic are there for chronic diseases.

• 4:07Speaker 01

  The core of our services are hypertensive, diabetes, and obesity.

• 4:13Stephen J. Dubner?

  Hypertension, diabetes and obesity, heart disease, too. On the face of it, there's nothing noteworthy about this predominance of chronic diseases. According to the CDC, the Centers for Disease Control and Prevention, 86% of US healthcare spending goes to treat chronic diseases. But what is noteworthy is that these conditions are much more concentrated among certain groups of people.

• 4:38Speaker 02

  We're talking about a twofold gap, at least a twofold gap, for the major killers, which would of course include heart disease and diabetes.

• 4:47Stephen J. Dubner?

  That's Sherman James. He is a professor of epidemiology at Emory University.

• 4:53Speaker 02

  In almost every category of health and disease, African-Americans lag behind whites, which is a very disturbing fact.

• 5:03Stephen J. Dubner?

  For decades, James has been studying the black-white gap in health. African-Americans, he says, have a substantially higher risk of death from heart disease and stroke. Blacks are as much as three times more likely than whites to have high blood pressure.

• 5:19Speaker 02

  And high blood pressure develops earlier in adult life for African-Americans compared to whites. It's more severe. So the number one contributor in terms of the persistent racial inequalities in heart disease is high blood pressure.

• 5:34Stephen J. Dubner?

  This racial health disparity has been known to researchers for decades. What isn't known is why.

• 5:40Speaker 02

  That's really an important fact. What accounts for that?

• 5:45Stephen J. Dubner?

  There are all sorts of hypotheses. One that Sherman James has put forward is called John Henryism.

• 5:54Stephen J. Dubner?

  That's from the folk legend about John Henry, the steel-driving man, the old-school, strong man who got into a race with a new-fangled steam hammer. John Henry won, but then he collapsed and died.

• 6:07Speaker 03

  John Henry's pappy woke him up one midnight.

• 6:11Stephen J. Dubner?

  The idea behind John Henryism is that blacks, because of discrimination and lack of opportunities, have had to work so much harder than whites, even in the same kind of jobs.

• 6:23Speaker 04

  I can turn a jack, I can lay a track, I can pick and shovel, too. Can you swing a hammer, boy? Yes, sir. I'll do anything you hire me to.

• 6:36Stephen J. Dubner?

  And all that hard work, Sherman James says, puts more stress on the body.

• 6:41Speaker 02

  The cardiovascular system, the immune system, the endocrine system, the reproductive system.

• 6:48Stephen J. Dubner?

  But even James, who's run study after study, who's an expert on African-American health, admits that none of this is conclusive.

• 6:56Speaker 02

  Despite efforts to uncover and elucidate the reasons for this persistent gap, we have achieved only limited insights.

• 7:05Stephen J. Dubner?

  In James's defense, it's really hard to definitively determine cause and effect when it comes to health outcomes. That's because we, as a society, don't run big randomized controlled trials on people's health to prove what does what. As a result, we know a lot less than we think we know. Just look at how much flip-flopping there's been in recent years about something as basic as the nutritional value of carbohydrates versus fats. When it comes to something as expansive, as variegated, as a health gap between Black Americans and white Americans, there are a lot of possible explanations. Does it have to do with diet, or smoking, or other behaviors? What about relative wealth or access to medical care? Maybe there's a genetic explanation.

• 7:48Speaker 02

  There's a lot that we, as a field, just don't know.

• 7:52Stephen J. Dubner?

  Well, there is another theory, the one we'll be talking about today, that says the black-white health gap might be related to something that all of us do every day, something that our body forces us to do every day, or, more typically, every night.

• 8:08Speaker 05

  One area that's been overlooked is sleep.

• 8:15Stephen J. Dubner?

  Lauren Hale is an associate professor of preventive medicine at Stony Brook University. That's on Long Island in New York.

• 8:21Speaker 05

  And I study sleep patterns. I call it the social patterning of sleep.

• 8:28Stephen J. Dubner?

  That's when people sleep, how long they sleep, how well they sleep. A lack of sleep has been linked to a variety of health problems, including diabetes, hypertension.

• 8:37Speaker 05

  Cardiovascular disease. There's associations with cancer.

• 8:41Stephen J. Dubner?

  And, as we all know, a lack of sleep can impair our cognitive functions, our decision-making. When Lauren Hale thinks about the huge racial gap in health that Sherman James described, she wonders if sleep just might be a missing link.

• 8:57Speaker 05

  Is it true that either racial minorities, low-educated, low-job-security individuals, people who live in high-risk neighborhoods, who experience fear at night, are these people, who clearly have some sort of social disadvantage, are they also not sleeping as well? And is this impaired sleep affecting not only their ability to function the next day, but their longer-term health outcomes?

• 9:26Stephen J. Dubner?

  That is just one of the questions about sleep we will try to answer today. But because sleep is such a big and interesting topic, and let's face it, it's also kind of weird, the fact that our bodies shut down entirely for roughly a third of our lives, because of all that, we are actually making two episodes about sleep. You will hear the second one next week. And, this being Freakonomics, we ask what the data have to say about sleep. As you will hear, even that is not always easy to figure out.

• 9:57Speaker 06

  We found that people with more education got more sleep, and people with higher incomes got more sleep.

• 10:04Speaker 07

  The answer is very, very clear. Those who earn more money per hour, those who have more education, they sleep less.

• 10:24Speaker 08

  From WNYC Studios, this is Freakonomics Radio, the podcast that explores the hidden side of everything. Here's your host, Stephen Dubner.

• 10:42Stephen J. Dubner?

  I don't know about you, but I personally love to sleep. I look forward to it. I like how I feel after a good night's sleep, and therefore, I take my sleep pretty seriously. You're talking to someone who does sleep with an eye mask and earplugs, just so you know. And that's because of my schedule for a bunch of years when I was traveling a lot in different time zones, whatever. I needed to sleep sometimes on planes or trains or whatever, in a hotel room when I'd get somewhere and it'd be daytime. And so I started using those sleep aids and then I just got used to them. And then they became Pavlovian for me. So like now, the minute I put in the plugs and the face mask, wherever I am, I just go to sleep. So I do it even at home.

• 11:24Stephen J. Dubner?

  It's just like a habit, which is kind of weird and annoying sometimes to my wife.

• 11:29Speaker 08

  Right.

• 11:32Stephen J. Dubner?

  I'm talking here with Lauren Hale, the sleep researcher we heard from earlier, and asking about her sleep preferences. Now, what about backside or tummy?

• 11:43Speaker 05

  I'm a tummy sleeper.

• 11:45Stephen J. Dubner?

  Hale likes the bedroom dark and cool, as do I, by the way. She likes a nice, flat pillow, not too fluffy. I go for medium fluffy. And Hale, like me, is married with two kids. But my kids are 14 and 13. Hers are much younger. The second one was born just a few months ago, which means that mom is not sleeping as much as she'd like.

• 12:06Speaker 05

  I wake up two to three times a night. My youngest one is not yet sleep trained. And it's very difficult to sleep well when you know you have to feed a child.

• 12:18Stephen J. Dubner?

  So most days Hale feels exhausted from lack of sleep. But she knows how lucky she is because her condition is temporary. As her kids get older, they'll sleep through the night.

• 12:27Speaker 05

  I know that my period of disrupted sleep, chronic disrupted sleep, is time delimited, where I understand from my research on low-income, high-financial-insecurity individuals that not everybody has that luxury of knowing when they will resume a full night's sleep on a regular basis.

• 12:49Stephen J. Dubner?

  Hale's research is focused on the racial and economic disparities of sleep. She stumbled on this topic as a graduate student. Her PhD from Princeton is in public affairs with a focus on population studies. Hale was trying to understand why some groups of people are so much healthier than others. The data she was using had a huge hole in it.

• 13:11Speaker 05

  I realized that we have data on the social experiences of individuals from childhood to middle age or older ages, and we were looking at what social factors explain health. And they had an enormous amount of data on these individuals on two-thirds of their lives, the waking hours. But they didn't have anything on what's going on during that remaining third at night.

• 13:38Stephen J. Dubner?

  That hole looks even bigger when you consider the scientific evidence on the relationship between sleep and health. Well, 20 years ago, we didn't know much about that. David Dingus is a professor of psychology and psychiatry at the University of Pennsylvania. In recent years, he says, researchers have found strong associations between lack of sleep and all sorts of medical issues, large and small. The experimental studies in the laboratory in both animals and humans show unequivocally that we gain weight fairly fast if we restrict our sleep. Because sleep is so central to health, Lauren Hale really wanted to find some data that showed how much and how well people sleep. And she did.

• 14:20Stephen J. Dubner?

  The CDC regularly conducts the National Health Interview Survey. One year, the survey happened to ask people about sleep.

• 14:27Speaker 05

  I was interested in the sleep disparities present among adults. And we found these stark differences.

• 14:35Stephen J. Dubner?

  The National Institutes of Health recommends that people get between seven and eight hours of sleep a night. In the CDC survey, nearly 31% of black respondents said they slept less than six hours a day, compared to just 23.5% of white respondents. The black respondents were also, perhaps not coincidentally, more likely to be very poor. This led Lauren Hale to consider the possibility that blacks and other minorities are more likely to suffer higher mortality in part because of the short sleep durations.

• 15:09Speaker 05

  Generally, people who have more opportunities, more control over their lives are also better sleepers.

• 15:17Stephen J. Dubner?

  And on the face of it, this would seem to make sense. You can envision a lot of connections between poverty and sleep, right? Your home environment might not be as conducive to good sleep. You're more likely to hold more than one job, maybe have a longer commute. And financial stress probably doesn't help anyone sleep better. But let's remember, the CDC survey was a survey. And survey data, as we've preached around here a lot, can be the lowest form of data.

• 15:45Speaker 06

  It's quite difficult to get accurate information about people's routine sleep behavior.

• 15:51Stephen J. Dubner?

  That's Diane Lauderdale. She is an epidemiologist at the University of Chicago. She says that sleep researchers have been trying all kinds of ways to get good sleep data.

• 16:01Speaker 06

  The obvious one is to ask people, how much sleep do you usually get at night? And that seems like it should be a great way to find out about sleep, just like if you ask people, how tall are you or how much do you weigh? You get a pretty good answer. It turns out, though, that sleep is hard. People don't actually know the answer to that question. We don't come with an internal clock. And so when people are sleeping, when they wake up, they have no idea usually how much they've slept.

• 16:31Stephen J. Dubner?

  Well, plus, I guess you also don't really know exactly when you fell asleep. I might have gotten in bed at 11, but I might not get to sleep till 11:25 or something. And I might not be aware of that, right?

• 16:41Speaker 06

  Right. Well, you'll know that it took you a while to go to sleep, but you might not be at all good at estimating how long it was, whether it was five minutes or 40 minutes. In addition, for many people, routines vary day to day. And so there's not only the problem of not knowing on any one particular night how much sleep you got, but in answering a question about routine sleep behavior, not really having a good sense of how to average behaviors over days when, in fact, you don't know how much you actually slept on any of them.

• 17:12Stephen J. Dubner?

  Indeed, the CDC survey that showed a big sleep disparity between whites and blacks simply asked people to provide a number for the total hours usually slept during a 24-hour day, including naps. There's another even more obvious problem with survey data, Diane Lauderdale points out. If you want, you can simply make up your answer.

• 17:33Speaker 06

  One approach people in surveys unfortunately often resort to is just giving an answer which they think will be a well-accepted answer to the person interviewing them.

• 17:42Stephen J. Dubner?

  A lot of people have heard the eight-hour figure. Where does that come from?

• 17:46Speaker 06

  I have tried to figure out where it comes from. I have no idea. That's a great question. If you have any leads, I'd be delighted to hear them.

• 17:57Stephen J. Dubner?

  On the other hand, some people may have reason to under-report their sleep. Maybe you're generally unhappy or unwell, and you figure that it's because you're not sleeping enough. Or maybe you're the kind of person who thinks that sleep is for suckers.

• 18:12Speaker 06

  There was a period in the 80s, 90s, when Margaret Thatcher or Bill Clinton really bragged about only needing four hours or five hours of sleep.

• 18:25Speaker 09

  What I came here tonight to promise you is that I will stay up late and get up early and work hard as long as it takes to turn this country around and give it back to the American people.

• 18:37Speaker 06

  And there was this period when being short-sleepers was really held up as evidence that you were leading an important life.

• 18:48Stephen J. Dubner?

  You probably still know plenty of people like that, don't you? Investment bankers, programmers, anyone working on a startup. There'll be time to sleep when I'm dead, they say. They are sleep-shaming the rest of us. But Diane Lauderdale thinks this trend is fading.

• 19:03Speaker 06

  I think far fewer people brag about how little they're sleeping. They're more likely to be complaining about how little they're sleeping and valuing sleep.

• 19:14Stephen J. Dubner?

  This may be because lack of sleep has recently been singled out as a really, really big problem. Last year, the CDC declared insufficient sleep a public health epidemic. It cited the long-term health implications and also warned that poor sleep leads to motor vehicle crashes and industrial disasters. The news media, which never lets a scary story go to waste, has been happy to chime in.

• 19:38Speaker 10

  You know, the lack of sleep carries a big price tag. There is a greater risk of poor health, obesity, accidents, and bad judgment. Wow, did we scare you there? Your health can take a serious hit if you're not getting enough sleep.

• 19:50Speaker 06

  There's a wide perception that people in the US are sleeping less than they used to, and the evidence for that is very weak. But it's so commonly accepted that people at this point say it without referring to data or any reference because people take it as the truth.

• 20:09Stephen J. Dubner?

  In other words, if you ask a simple question like, how much does the average American sleep each night? And how much has that amount changed over time, if any? Well, the data to answer those questions aren't very clean. One commonly cited study, Diane Lauderdale says, was a survey conducted in 1960 by the American Cancer Society. It had the virtue of being a large survey, a million people, who were asked about medical history, whether they smoked, and so on.

• 20:38Speaker 06

  They happened to ask people how much they usually slept in that baseline assessment.

• 20:43Stephen J. Dubner?

  This survey concluded that Americans typically slept eight to nine hours a night, with just 2% of respondents sleeping six or fewer hours a night. Fast forward now 35 years to 1995, when the National Sleep Foundation did another sleep survey. The NSF happens to take money from pharmaceutical and mattress companies, but they claim independence and academic rigor. Lauren Hale, for instance, the sleep researcher at Stony Brook, is on the NSF board. Anyway, this survey found that nightly sleep had dropped to seven hours. And then, in 2007, the CDC survey reported that 30% of American adults were sleeping six or fewer hours.

• 21:26Stephen J. Dubner?

  And these findings were often getting compared with the 1960 data.

• 21:30Speaker 06

  People picked up on the distribution of sleep reported from 1960 in that study as being this baseline of how people slept.

• 21:39Stephen J. Dubner?

  But there's at least one big problem with the American Cancer Society survey. Volunteers recruited friends and family to participate, so the sample set wasn't even trying to represent the population as a whole.

• 21:51Speaker 06

  There were almost no minority group members in it. They were well-educated, wealthier than the general population.

• 21:58Stephen J. Dubner?

  So Lauderdale is not buying the argument that we're all sleeping less. In fact, she says she's found some evidence to suggest that teenagers at least spend more time in bed than they used to.

• 22:08Speaker 06

  So that strongly suggests that there's not a big trend towards less sleep.

• 22:16Stephen J. Dubner?

  Lauderdale is also cautious about presuming a concrete link between sleep and health.

• 22:23Speaker 06

  The evidence that sleep matters for health, while growing and to some extent pretty compelling, is not as strong as the evidence that physical activity and diet matter for health. I think we really need to know better how sleep is related to health. It's absolutely clear that sleep is related in some ways. We just don't have a lot of clarity about which those are and exactly how it matters.

• 22:56Stephen J. Dubner?

  So what do you do if you want some clarity about sleep and you don't want to just rely on self-reported data? In recent years, researchers have turned to something called actigraphy. That means you attach a small accelerometer to someone's wrist, think of a Fitbit, and it tracks their arm movements.

• 23:13Speaker 06

  So you can get a pretty good estimate of when people are asleep, but of course, it's just, it's an estimate. But the good thing is, it's, it's objective in that it doesn't have all of these reporting problems that the sleep survey questions have.

• 23:28Stephen J. Dubner?

  A few years back, Lauderdale and some colleagues collected their own data on sleep patterns, with some of the data collected by wrist actigraphy. This was an add-on to a larger longitudinal study that years earlier had begun following young, healthy adults in Chicago.

• 23:44Speaker 06

  This was done after people had been in the cohort for about 20 years, and they were enrolled when they were young adults, 18 to 30. So at this point, they were mostly in their 40s. The population was about half-white and half-African-American, and that was by design, how the study was set up in the 1980s. They, at one time, had all lived in the Chicago area, but were not necessarily in the Chicago area anymore. And there were about 650 people who participated in this sleep add-on study.

• 24:17Stephen J. Dubner?

  The data from this study seemed to confirm the self-reported data that Lauren Hale had looked at.

• 24:22Speaker 06

  What we found was, on average, really large gender and race disparities. Women, on average, slept about an hour longer than men. And whites slept, on average, about an hour longer than African Americans, so that there was combined, almost an hour and a half difference, on average, between African American men and white women, with the white women sleeping more. And the race difference was extremely surprising because it was so large.

• 24:56Stephen J. Dubner?

  In terms of race, what's the best explanation for why whites slept longer, better than African Americans?

• 25:03Speaker 06

  So some of the difference we found had to do with economic and education factors, but not all of it. So with this actigraphy estimate, and I'm intentionally highlighting that, we found that people with more education got more sleep and people with higher incomes got more sleep.

• 25:27Stephen J. Dubner?

  OK, so based on relatively objective data, it does seem that people with more education and higher incomes get more sleep and that whites get more sleep than African Americans. That's a nice, clean, bold conclusion, isn't it? Come on, people, this is Freakonomics Radio. We're not just going to leave it there, are we?

• 25:50Stephen J. Dubner?

  No, we are not. Coming up after the break. We talked to an economist who looked at a truly massive data set, charting the daily habits of roughly 150,000 Americans. And he found what seemed to be an opposite conclusion.

• 26:06Speaker 07

  You can adjust for anything else you want. Education, age, marital status, presence of kids, immigrant status. Blacks sleep more than whites on average.

• 26:17Stephen J. Dubner?

  And how well do sleep researchers follow their own sleep advice?

• 26:22Speaker 05

  I admit, I use screens at bedtime. I should not, but screens are enticing and relaxing.

• 26:30Stephen J. Dubner?

  And one more thing before we go to the break. For this episode, we asked you, our podcast listeners, to tell us about your sleep habits. You responded in great number and with quite a few, shall we say, unexpected answers, like the sleeping head to feet thing.

• 26:47Speaker 11

  Hey, guys. I just woke up and I thought I'd send this to you and let you know how I slept.

• 26:54Speaker 12

  My name is Matt King, and I live in Menifee, California.

• 26:57Speaker 11

  Not well, sort of tossed and turned.

• 27:00Speaker 12

  I will sleep through earthquakes, lightning storms, the dogs barking, my wife being irritated for whatever reason. Never had a problem sleeping.

• 27:10Speaker 11

  My husband's not in town. And I never, I never sleep well when he's not here.

• 27:16Speaker 13

  My name is David Taylor. My name is Paul Heinisch. I live in Campbell River, British Columbia, Canada. I get anywhere from six to six and a half hour sleep. And I sleep at the opposite end of my wife's side of the bed, head to feet. I start out with a weird sleeping pattern that I have to sleep with my feet up where my wife's head is and my head down there as close to the TV as possible with the TV on the full time.

• 27:47Speaker 14

  Hello, Freakonomics. This is Mohamed Al-Sari.

• 27:50Speaker 15

  My name is Anne.

• 27:52Speaker 14

  I am originally from Saudi Arabia, but I currently live in Scottsdale, Arizona.

• 27:57Speaker 15

  I cannot wear socks when I'm sleeping or else I get really thirsty at night.

• 28:02Speaker 14

  I usually sleep with...

• 28:05Speaker 14

  Two pillows under my head and one pillow. This is important. One pillow between my thighs. I just love it.

• 28:13Speaker 15

  I used to smoke a lot of weed before I went to bed. But when you quit cold turkey, you remember your dreams like hardcore, which is really stressful. I hate remembering my dreams.

• 28:24Speaker 16

  My name is Heath Einstein. I am age 39 and I live in Dallas, Texas.

• 28:29Speaker 14

  I at least try to get one body part touching. So I'll try to slip my leg underneath my wife's legs.

• 28:37Speaker 16

  I don't like to be touched while I'm sleeping, much to my wife's chagrin. No snuggling. There's an imaginary line that I prefer not be crossed.

• 28:47Speaker 15

  It's awesome to wake up with the sun.

• 28:49Speaker 16

  I prefer a room that is pitch black, where you can't see even a finger right in front of your face.

• 28:55Speaker 17

  In order to help get to sleep, I take two melatonin, a baby aspirin, and usually a Bombay Sapphire Martini.

• 29:05Speaker 18

  My name is Laura Clem and I'm from Colorado, but I now live in Hong Kong.

• 29:10Speaker 19

  Nice, fresh, cold pillow. And you flip it over to the cold side. I always like that. Helps me fall asleep.

• 29:14Speaker 18

  Before bed, I usually get really thirsty, so I have to take a drink. But then I'll have to pee. So then I have to pee. And then I'm thirsty again, so I'll take another drink. Then I won't go to bed right away, so I'll have to pee again. It's a vicious cycle.

• 29:27Speaker 17

  So that's my story.

• 29:29Speaker 18

  I guess I better sign off for now so I can go to bed, get some sleep.

• 29:37Stephen J. Dubner?

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• 30:20Stephen J. Dubner?

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• 30:42Stephen J. Dubner?

  Freakonomics Radio is sponsored by Southern New Hampshire University. The best investments are the ones you make in yourself, and no one knows that better than Southern New Hampshire University. With more than 200 online degree programs, no set class times and low online tuition, Southern New Hampshire University is built to fit your life today and set you up for success tomorrow. Education is an investment. Why not make it a smart one? Apply for free at S N H U dot E D U slash Freakonomics.

• 31:14Stephen J. Dubner?

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• 31:52Stephen J. Dubner?

  Since we are exploring the causes and consequences of sleep, we asked to hear about your sleep habits.

• 31:59Speaker 16

  I like to think of myself as a bit of a sleep snob.

• 32:03Stephen J. Dubner?

  So we thought we'd ask the same thing of one of the first economists to ever study sleep. We're getting a little personal here. That's Dan Hamermes.

• 32:12Speaker 07

  I'm professor of economics at Royal Holloway University of London and emeritus professor at the University of Texas at Austin.

• 32:19Stephen J. Dubner?

  Hamermes started studying sleep in the late 1980s, in part because he wasn't getting enough.

• 32:24Speaker 07

  I've always viewed myself as a pretty bad sleeper.

• 32:26Stephen J. Dubner?

  Some nights he'll sleep for eight hours, but then only six the next. His wife worries about him. She won't let him work past 9:00 PM, so he tends to get into bed pretty early.

• 32:36Speaker 07

  I've been married for 48 and a half years. I like to sleep on my left side. I insist on being on the right side of the bed. I sleep on my left side and cuddle up to my wife who's sleeping on her left side. If I'm by myself in a hotel, as I am occasionally, I sleep on my left side and I hug a pillow in place of my wife.

• 32:58Stephen J. Dubner?

  When he is not hugging his pillow, or his wife, Hamermes likes to crunch data. He's a big fan of the American Time Use Survey, which is produced by the Bureau of Labor Statistics. It covers roughly 150,000 people. But unlike the typical survey, which just asks people to say how much time they spend doing a particular activity, sleeping, or doing housework, or whatever, the American Time Use Survey asks them to account for every minute out of all 24 hours. This is meant to lessen the bias against particular activities.

• 33:33Speaker 07

  I think it's a wonderful thing. They started this in 2003. It is by now the world's largest ongoing, indeed the only ongoing continuing study of how people spend their time. A tremendous revolution in data for people like myself.

• 33:49Stephen J. Dubner?

  When we asked him, Hamermes was good enough to look into the sleep numbers from the ATU. Is it ATUS or ATIS?

• 33:57Speaker 07

  There's a discussion of this among those who produce it. They like to say ATUS. My time is more valuable. I say ATIS.

• 34:05Stephen J. Dubner?

  Okay, so what do the ADIS data tell us about sleep?

• 34:10Speaker 07

  Well, it tells us what you expect, namely, the average person sleeps somewhere between eight and nine hours, so that's pretty much what you think.

• 34:18Stephen J. Dubner?

  All right, any variance by gender?

• 34:21Speaker 07

  Well, we know that women, on average, sleep about eight minutes more per night than do men, which is not a heck of a lot, but it adds to an hour a week. That's the first thing.

• 34:31Stephen J. Dubner?

  But that gender gap changes when you throw a baby into the equation.

• 34:35Speaker 07

  Among people who have little kids ages zero through two, for men, that results in about eight minutes per night of reduced sleep compared to other men who have no kids, whereas among women, it results in 16 minutes per night, almost close to two hours per week of reduced sleep. So despite the alleged great efforts that men are making these days to increase equalization of behavior in the household, in fact, sleep reductions are much bigger among women than among men who have little kids.

• 35:11Stephen J. Dubner?

  Hammer Mesh found the same result in the data from 1975, so it would seem that not much has changed. By the way, married men and women both sleep about eight minutes less per night than their single counterparts. And since we're talking about American sleep habits, how do people born in the US sleep compared to immigrants?

• 35:31Speaker 07

  Immigrants sleep more, given their education, their age, their gender, number of kids, marital status. And that's especially true for male immigrants. For men, it's 20 to 25 more per night, which is a huge amount.

• 35:46Stephen J. Dubner?

  That's 20 to 25 minutes per night, which does suggest that America tends to be a bit more sleepless than the rest of the world. But let's get back to what we're here for, to look at differences between high and low-income sleepers and how those differences might influence something as important as life-threatening disease. Remember, the other data we've been discussing has all suggested that higher-income, higher-education people sleep more than low-income, low-education people.

• 36:14Stephen J. Dubner?

  What does this ADIS data have to say?

• 36:16Speaker 07

  The answer is very, very clear. Those who earn more money per hour, who have better, what we call in economics, opportunity cost of working, they sleep less. Those who have more education, because education increases your opportunities in the labor market, one should expect, and one observes that the more educated you are, the less you sleep, given your demographics of age, ethnicity, marital status, and presence of kids. It doesn't differ much between college dropouts and people with PhDs. The big difference is between those who have some college or more compared to high school grads or high school dropouts. And we're talking 15, 20 minutes for men per night, which is a lot.

• 36:59Speaker 07

  I mean, that's, you know, that's a couple of hours out of your 168 per week. That's a substantial amount.

• 37:05Stephen J. Dubner?

  And what about the black-white sleep gap? Again, the other data suggested that blacks sleep less than whites. Hammermez says that's wrong.

• 37:14Speaker 07

  You can adjust for anything else you want. Education, age, marital status, presence of kids, immigrant status. Blacks sleep more than whites on average.

• 37:24Stephen J. Dubner?

  It would seem that on average, that is true. The ADIS data show that black men, for instance, sleep eight or nine minutes more per night than white men. For women, the gap is even wider. Black women sleep roughly 20 minutes more than white women. But Lauren Hale, the sleep researcher we heard from earlier, says that average sleep duration is not the key metric. What you want to do, she says, is break down the ADIS data further. You want to look at people who sleep fewer than six hours a night, short sleepers, as researchers call them, and also the very long sleepers. Dan Hammermez was focusing on the averages.

• 38:03Speaker 05

  I think he's wrong. Because I've looked at the data. And I think you have to separate out who are the short sleepers and who are the long sleepers.

• 38:11Stephen J. Dubner?

  So, we went back to Dan Hamermes, asked him to get on his computer again and rerun the regression.

• 38:16Speaker 07

  Let me just look at this for a second if I could. Okay.

• 38:20Stephen J. Dubner?

  He found something he wasn't expecting.

• 38:22Speaker 07

  The average black, be it male or female, is more likely to sleep very short hours, less than six hours per night. Also, much more likely to sleep very long hours, more than 11 hours a night. In other words, there are more extreme sleep by blacks than by whites, both very short sleep and especially very long sleep. And that's a new finding. I'd not seen that before. The fact seems incontrovertible and really neat.

• 38:48Stephen J. Dubner?

  Really neat, meaning really persuasive and useful if you're trying to connect sleep to overall health. Sleeping too little, or too much, we should say, are both associated with poor health. And one more thing. While the ADIS data do argue that high earners sleep less than low earners, the University of Chicago epidemiologist Diane Lauderdale says that conclusion is also tricky.

• 39:12Speaker 06

  What I believe is going on is that people with more money spend less time in bed or a lot less time to sleep, but they spend a higher proportion of the time they do a lot actually sleeping.

• 39:29Stephen J. Dubner?

  So they're more efficient in bed?

• 39:31Speaker 06

  Exactly.

• 39:32Stephen J. Dubner?

  Efficient sleeping, I should say. They may be more efficient in bed in every way, but they're more efficient sleeping in bed.

• 39:39Speaker 06

  Yes, I'm not discussing that. So that may have to do with just overall how they think about their time, because their time is worth more.

• 39:51Stephen J. Dubner?

  We circled back to Sherman James, the Emory epidemiologist who studies the black-white health gap. We asked what he thought of the possibility that sleep might be a missing link. Said he never thought of it, but it does seem plausible. He pointed out that our blood pressure drops to a nice baseline level when we sleep. Sort of an opportunity for the cardiovascular system to rest. But for African Americans, he says, blood pressure doesn't dip quite as much at night as it does for whites.

• 40:22Speaker 02

  And so what we're looking at then is a reduced ability of the cardiovascular system to recover. And that's going to have effects. If once blood pressure is higher, even while you are sleeping, then that's going to add to your long-term risk for heart disease.

• 40:36Stephen J. Dubner?

  Lauren Hale from Stony Brook believes the racial sleep gap may be driven in part by environmental factors. African Americans are more likely to be poor and live in a neighborhood that is not optimized for sleeping.

• 40:48Speaker 05

  The high-risk neighborhood is noisier. The apartments are crowded. The apartments aren't as well air-conditioned or heated because it's a low-income household. There is more light outside on the street. There's an airplane flying overhead. There's a street brawl going on outside. Maybe it's something about being in that neighborhood. So what if you take that person out of the neighborhood and see how they sleep in the country or in the suburbs? Would their sleep improve? We haven't done that experiment. But the question is, well, is it really living in a high-risk neighborhood that's the problem? Or is it more of a compositional problem of who lives in a high-risk neighborhood? And who lives in a high-risk neighborhood, but are the same type of people we've already

• 41:32Speaker 05

  reported, are at higher risk of poor sleep?

• 41:35Stephen J. Dubner?

  Hale is currently doing research with a project called the Fragile Families and Child Well-Being Study. It's following nearly 5,000 kids born in the US between 1998 and 2000, most of them to unwed parents. Now the kids are teenagers, and Hale's team is using wrist actigraphy to track their sleep.

• 41:55Speaker 05

  What we can tell from looking at the earlier waves of data is that as early as ages three and five, and even at nine, too, we're finding that black children are sleeping less than white children. They're also having fewer bedtimes and fewer bedtime routines, and they're less likely to use the bedtimes. And so, early on, these parenting differences around bedtime

• 42:21Speaker 05

  Might have lasting impacts. At age five, we in particular looked at cognitive outcomes and behavioral outcomes. And most strongly, we found that cognitive outcomes were higher among children who had a regular language-based bedtime routine, reading a story or singing a song.

• 42:39Stephen J. Dubner?

  It strikes me that I've seen so much messaging talking to us about nutrition and safe driving and anti-alcohol and anti-drug and anti-smoking, but I've never seen that I can recall a pro-sleep message, really. Why is that or why haven't we seen that? Is it because it's not really that important or just because we haven't collectively come to appreciate the power of good sleep on a productive life?

• 43:04Speaker 05

  I think you're absolutely right. Sleep has not yet been fully recognized as an important health behavior. The Centers for Disease Control has every decade a set of goals for the health of the nation, and it wasn't until the 2020 initiative that sleep made the list of what we should aspire to as a country. And to the sleep community, that seems ludicrous. We're like, it's obvious that sleep is essential for not just cognitive well-being, but for heart health, for psychological well-being, for interpersonal relationships. So unlike in the case of smoking, which is a huge public health success story, where

• 43:47Speaker 05

  you can say, we know smoking is bad for one's health, the recommendation is to quit smoking, there wasn't a clear recommendation on what duration and quality of sleep was expected. So it's more nuanced.

• 44:02Stephen J. Dubner?

  The National Sleep Foundation and others have issued a menu of sleep hygiene recommendations. Some of them are pretty obvious. You want to avoid caffeine, nicotine, and alcohol too close to bedtime.

• 44:15Speaker 05

  Alcohol, it may help you fall asleep, but the quality of sleep is reduced.

• 44:19Stephen J. Dubner?

  The guidelines also suggest exercise, creating a regular bedtime routine, and avoiding screens of all sorts from at least 30 minutes before you sleep. Lauren Hale, even though she is a bona fide sleep researcher and is on the board of the National Sleep Foundation, says she has a hard time with that last one.

• 44:37Speaker 05

  I admit, I use screens at bedtime. I should not, but screens are enticing and relaxing in some ways, even though the research shows that the light and the content from Reading a screen in bed or at bedtime are not conducive to sleep.

• 44:55Stephen J. Dubner?

  And how persuasive is that research in your mind?

• 44:57Speaker 05

  It is on the brink of becoming even more persuasive, but in December Anne Marie Chang and Chuck Seisler at Harvard published an experimental study where they kept people in a laboratory at night. Some people were reading the same content on a book and some people were reading it on an iPad. And those people who read it on an iPad were shown the light, I mean, they had exposure to the light and had trouble falling asleep and lower quality sleep. So it's persuasive.

• 45:26Stephen J. Dubner?

  So you say you are, you do use some screens. Do you use screens for reading, watching TV? What do you do?

• 45:31Speaker 05

  I'd say probably before children and before I had an iPad, I would watch TV at night. Now I look at my phone or I look at an iPad.

• 45:41Stephen J. Dubner?

  And what are you looking for? When you say I look at, what are you looking for?

• 45:44Speaker 05

  I read.

• 45:45Stephen J. Dubner?

  Okay. You read like books or you reading emails and Instagram and Facebook?

• 45:49Speaker 05

  Yeah, something like that. Emails, I respond to email or I read posts on Facebook. I read articles. Nothing heavy. It's light.

• 45:58Stephen J. Dubner?

  But I would think that, it's funny because when you say nothing heavy, because I hear people say that all the time, like, I just look at that kind of stuff. And I would argue personally, for me at least, and this is just an N of one, that that would be way more disruptive or distracting to sleep than reading an actual book. Because when I read a book,

• 46:14Speaker 05

  Right.

• 46:15Stephen J. Dubner?

  I'm reading it kind of for pleasure and also to learn, right, and I'm focused. And it doesn't distract me in a way that like seeing, oh, that's what that person is up to and I wonder what that means for me and my family and my life. And oh my goodness, so and so went to Antarctica. I wonder if they're going to bring me back some frozen penguin poo as a gift. Wouldn't that be great, you know? And so when you say that it's just light stuff, see, to me, and again, to my untrained brain, I would think that's the worst thing you could possibly do.

• 46:43Speaker 05

  You're completely winning in this argument. I should not be reading my iPhone before bed. You're inspiring me to take my own advice and try it for a week. Put the screens down. I did a screen-free week last year, actually, with my kids. At that point, one kid, it wasn't that hard. But I think the real challenge is try it for a week and see if you feel better, if you're sleeping more, if you're going to bed earlier, and see how you feel.

• 47:14Stephen J. Dubner?

  OK, so I want to make this concrete. So are you saying, right here and right now, that you vow from today going forward for one week, that you're going to do what? That you're going to put all your screens outside of the bedroom at a certain time, let's say? Is that what you're offering?

• 47:28Speaker 05

  Absolutely.

• 47:28Stephen J. Dubner?

  OK, what time?

• 47:30Speaker 05

  From nine o'clock onwards. Of course, I have a little baby who falls asleep at seven, so I try to fall asleep even sooner. But yes, from nine o'clock onwards, including when I'm up in the middle of the night nursing, I vow not to look at my iPhone, my smartphone, or my television until seven in the morning.

• 47:49Stephen J. Dubner?

  Awesome. OK, so here's what's going to happen. We're going to get you back on the line in a week. And we want to know what happened. And we want to then know, obviously, if what you learn about yourself might inform somehow where you want to go down the road for future sleep research. Does that sound OK?

• 48:05Speaker 05

  That sounds fantastic.

• 48:07Stephen J. Dubner?

  All right, talk to you then.

• 48:08Speaker 05

  Talk to you then. OK, bye-bye.

• 48:09Stephen J. Dubner?

  Thanks so much, Lauren. Bye-bye.

• 48:15Stephen J. Dubner?

  OK, that's our sleep cliffhanger. Will Lauren Hale be able to put away all her devices before bedtime for a whole week? Next episode, you'll hear.

• 48:24Speaker 05

  I was shocked at how many times I wanted to check my phone, turn on the TV, go to the computer.

• 48:31Stephen J. Dubner?

  But also, next episode, does sleeping more help you earn more money?

• 48:37Speaker 20

  We find that permanently increasing sleep by an hour per week for everybody in a city increases the wages in that location by about 4.5%.

• 48:46Stephen J. Dubner?

  And we hear more from you, our listeners, on how you optimize your sleep.

• 48:52Speaker 21

  My name is Spencer Rothfuss. I'm 16 years old and live in Omaha, Nebraska. I sleep fully dressed in the next day's clothes, so I'm ready to go in the morning.

• 49:00Stephen J. Dubner?

  And finally, scientific proof that the early bird really does get the worm.

• 49:05Speaker 22

  There was a significant differential in the sense that the morning type people earns four or 5% more than evening type people.

• 49:13Stephen J. Dubner?

  All of that next time on Freakonomics Radio.

• 49:23Stephen J. Dubner?

  Freakonomics Radio is produced by WNYC Studios and Dubner Productions. This episode was produced by Christopher Worth. It was mixed by Rick Kwan and Merritt Jacob. Our staff also includes Irvva Gunja, Jake Howitt, Greg Rosalsky, Kasia Mahalovich, Alison Hockenberry, and Caroline English. And would you do us a favor? Our producing partner, WNYC Studios, wants to learn more about your radio listening habits. So please visit wnyc.org/participate to take their brief survey. That's wnyc.org/participate. And thanks.

• 50:05Stephen J. Dubner?

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• 50:38Stephen J. Dubner?

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• 51:09Stephen J. Dubner?

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• 51:40Speaker 23

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