Episode 203: Is Losing an Hour of Sleep Really That Big a Deal?
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On This Episode
With daylight saving time coming up this weekend, one might wonder whether losing a single hour of sleep is that big of a deal. In this episode, we talk with a neurologist who specializes in daily rhythms about what might be lost along with that hour—and finally answer the question, Are you getting enough sleep?
This episode was recorded on December 14, 2023.
Released on March 7, 2024.
Guest
Elizabeth B. Klerman is a professor of neurology at Harvard Medical School, a physician at Brigham and Women’s Hospital, and a neurologist at Mass General Research Institute whose research focuses on the influences of circadian and sleep rhythms in normal and pathological states. With her colleague Charles Czeisler, Klerman convened a Radcliffe Exploratory Seminar to consider how to better publicize the physical effects of daylight saving time.
Related Content
Boston Globe editorial: Making Daylight Saving Time Permanent Would Mean Losing Sleep—and Lives
Elizabeth B. Klerman: Harvard Medical School Bio
Credits
Ivelisse Estrada is your cohost and the editorial manager at Harvard Radcliffe Institute (HRI), where she edits Radcliffe Magazine.
Alan Catello Grazioso is the executive producer of BornCurious and the senior multimedia manager at HRI.
Jeff Hayash is a freelance sound engineer and recordist.
Marcus Knoke is a multimedia intern at HRI, a Harvard College student, and the general manager of Harvard Radio Broadcasting.
Heather Min is your cohost and the senior manager of digital strategy at HRI.
Anna Soong is the production assistant at HRI.
Special thanks to Cabin 3 Media for their invaluable contributions to the editing of this podcast episode.
Transcript
Ivelisse Estrada:
Hello, and welcome back to BornCurious. I’m your cohost, Ivelisse Estrada.
Heather Min:
And I am your cohost, Heather Min.
Ivelisse Estrada:
Coming to you from Harvard Radcliffe Institute, one of the world’s leading centers for interdisciplinary exploration, this podcast brings together scholars, students, artists, and doers. Our conversations traverse current affairs, scientific breakthroughs, cutting-edge research, art making, and storytelling.
Heather Min:
Today on the program, we’re going to talk about a topic central to all our lives: sleep. In fact, you’re probably dreading springing ahead this coming weekend as part of daylight saving time. No one enjoys losing a precious hour of sleep.
Ivelisse Estrada:
I know I don’t. But what does this loss mean for our health and for our society? To try to answer this question, we are here today with Dr. Elizabeth B. Klerman, who is a professor of neurology at Massachusetts General Hospital and Harvard Medical School, and an expert on the biological rhythms that sleep is a part of.
Heather Min:
With her colleague Charles Czeisler, Klerman convened a Radcliffe exploratory seminar to consider how to better publicize the physical and societal effects of daylight saving time. And we should mention that the participants included not only sleep scientists but also economists and people involved in public policy.
Ivelisse Estrada:
So let’s dig in. Hi, Elizabeth. Thanks for joining us.
Elizabeth B. Klerman:
Thank you very much for inviting me to join you two for what I anticipate will be a very interesting and fun conversation.
Heather Min:
We’re so excited to have you here. I would love to start us off with a rather simple question. Why is sleep good for us?
Elizabeth B. Klerman:
We know that it is good for us. And one of the founders of the field of sleep medicine, Allan Rechtschaffen, said, “If sleep does not serve an important purpose, it’s the greatest mistake evolution has ever made.” We know that when you’re asleep, you are not doing things that most people usually assume are important for survival. So most people usually assume you need to eat, which you don’t do when you’re asleep; you need to procreate, which you don’t do when you’re asleep; and you need to defend yourself, which you don’t do with your sleep.
And yet, sleep has been defended evolutionarily in basically every organism that we know of. So we know it has some important purpose. I think it has multiple important purposes. So we know that if you don’t get enough sleep, there’s changes in your immune function. Your immune function is how you fight diseases. There’s changes in your cardiovascular function. There’s changes in your mood—
if you’ve ever had a child who’s tired, you know what happens to mood—in your ability to perform objectively, drive a car, do something like that. So we know that all of these things require sleep, but we don’t know what about sleep exactly that causes it. We just know that restorative factors for many of these biological processes occur during sleep.
Heather Min:
What you’re saying is sleep makes you feel better, makes your brain work better. Do we know exactly why and how?
Elizabeth B. Klerman:
Why is always a hard question in biology. We just know right now that these two are correlated. The question is whether there’s causal relationships. So we know that if people do not get enough sleep, their body does not function as well. Many scientists are trying to figure out the exact details of brain and other function that are the link between insufficient sleep and adverse effects on biology.
Heather Min:
How much is enough sleep?
Elizabeth B. Klerman:
The easy way to answer is if you wake up without an alarm clock. So by definition, if you need an alarm, you’re not getting enough sleep. The second issue is, how much do you sleep if you have lots of time when you don’t have to get up? And I realized it doesn’t apply to people with children, second jobs, and dogs. The studies that have been done about how much sleep you need depends on your age.
So we know how much sleep people need when they are babies is 10 to 15 hours. For adolescents, it’s 7 to 9 to 10 hours, which almost no high school students are getting. And then for older adults, it’s still seven to nine hours. The question about how much sleep do you need is, once again, need for what? So how much sleep you need for memory may be different than the amount of sleep you need for metabolism, which is how your body processes what you eat—and when it doesn’t work, you get something like… you sometimes have diabetes—or how much do you need for your mood.
So we don’t know how much is needed for each of these. We just know based on a lot of evidence that if people get less than the recommended amount of sleep, they don’t do well. I’d like to make a little aside and talk about a fun experiment that we did at the Brigham and Women’s Hospital.
Ivelisse Estrada:
Ooh.
Heather Min:
Ooh.
Elizabeth B. Klerman:
Yes. And what we did is we asked people who were healthy—so they had no physical ailments, they weren’t taking medications, and they didn’t have sleep disorders—and we said, “Sleep as much as you usually do for three weeks, and we’re just going to keep track of how much sleep you get.” And then we looked at that. And then for the last week, we took the average. We looked at what they’d done before, and we said, “Okay. Please keep this schedule for the last week before you come into the hospital.” And people slept anywhere between 5 ½ and 10 hours. That’s totally fine.
Then we brought them into the hospital to do a research study. And the first night, we had them sleep at their usual time and duration, just wanted to see how much sleep they actually got when we put on what are called electrodes. So we put these wires on their head to measure their brain waves, next to their eyes to measure their eye movement, and on their chin to measure their muscle movement, because if you ever look at somebody who falls asleep, you can see that their eyes roll up in their head and they close their eyes, and their muscles relax.
So the way you look and monitor somebody’s sleep is you do what’s called a poly (for many)-somno (for sleep)-gram (like you’re recording something). So you measure the brain waves, the eye movements, and the chin. Then the next morning, we did what’s called a multiple sleep latency test.
So when we looked at the people who said, “This is how much sleep I need. I’m getting all the sleep I need at home,” and we brought them in for testing, the people who got less than eight hours of sleep were falling asleep much faster than the people who got more than eight hours of sleep at home. Some of the people were even falling asleep within five minutes, which is considered pathologically sleepy, and even some of the people were falling asleep before the technician had left the room.
So there was a very interesting relationship between how much sleep people got at home versus how quickly they fell asleep in a lab with all these electrodes all over their brain and face. What was interesting was, if you looked at older and younger people, the older people, if they had the same amount of sleep at home as the younger people, took longer to fall asleep, which suggests that the sleep may indeed change with age.
Then the next thing we did was we gave people a 12-hour sleep opportunity at night. So guess how much sleep people got on average on the first night?
Ivelisse Estrada:
I’m going to go with eight hours.
Elizabeth B. Klerman:
Oh, no, no, no.
Ivelisse Estrada:
No?
Heather Min:
A full 12.
Elizabeth B. Klerman:
On the first 16 hours of sleep opportunity, the average was approximately 12 hours.
Heather Min:
Wow.
Elizabeth B. Klerman:
So all of these people were saying, “Oh, no, no. I’m getting enough sleep.” Everybody on the first night was sleeping more than they usually do. On the second night, the people who usually slept nine hours were back at around nine hours, but the people who were sleeping five or six hours were still sleeping more than five or six hours for three, four, or five days. So we sometimes joke, “A weekend is not enough.”
Sleep is what’s called a homeostatic process, that the body cares, has a set level. And then if you’re below the set level, it first goes higher and then comes back down again.
So if sleep is homeostatically regulated, you don’t get enough sleep at home, you’re not getting as much as your body thinks you should, it’s first going to bounce up to recover some of the loss, and then it’s going to come back down to that level. Does that make sense?
Ivelisse Estrada:
Yes.
Elizabeth B. Klerman:
So this suggests that the younger people, if they’re given opportunity for sleep, should sleep—or can sleep—more than eight hours, slightly more than eight hours, which means you need to be in bed for more than eight hours. And for older people, it’s slightly less than eight hours. This, however, was only looking at how much people spontaneously sleep. We still weren’t looking at immune function, metabolic function. We were looking a little at mood.
Ivelisse Estrada:
Mm-hmm. And when you say younger and older people, how do you define that? How do you define older and younger?
Elizabeth B. Klerman:
For this particular study, I think it was around 18 to 35 and around 55 and older. I don’t remember the exact ages.
Ivelisse Estrada:
Okay. Yeah. I was just curious. So what sparked your interest in sleep?
Elizabeth B. Klerman:
So I’m going to answer a slightly different question and tell you what sparked my interest in biological rhythms.
Ivelisse Estrada:
Great.
Elizabeth B. Klerman:
I was an undergraduate, and there was a paper. I can even still imagine the layout on the page of how heavy water, which is D2O instead of H2O—so there’s a slight difference in the composition of the water—changed the free-running period, so changed the circadian rhythm of mice. And I thought that was fascinating. I no longer remember what the original paper was about. And so, from that, most of the studies about rodents are actually about activity levels.
And as an undergraduate, I did a research project. And it turns out most of the effects we were looking at were related to daytime versus nighttime, not the actual intervention we were trying to do, and that brought me into circadian rhythms. And then for my doctoral work, I started looking at the interaction of circadian rhythms and sleep. So I came to sleep from looking at the most obvious manifestation of circadian rhythms rather than starting with sleep.
Ivelisse Estrada:
And what are circadian rhythms?
Elizabeth B. Klerman:
Circadian rhythms are approximately 24-hour rhythms in biology. They’re generated inside a body, actually inside many individual cells, and they’re self-sustaining. So you don’t need the outside world environment in order to have these rhythms. Of interest, and it’s something I spend time with as part of my research, is that most experiments that have been done are actually not of your circadian rhythms, they’re of your daily rhythms. Because I’m not just looking at your circadian rhythm when I look at your core body temperature or when I look at your alertness. I’m also looking at whether or not you moved around or whether or not you had a meal, or whether or not other things then happened. And so, one of the difficulties of doing circadian rhythms experiments is separating these evoked effects from movement or eating or something else from the actual internal body clock, circadian rhythm.
Heather Min:
How does daylight or light affect the body?
Elizabeth B. Klerman:
For circadian rhythms, light is the most important synchronizer of your body’s clock to the outside world. So it’s how your body clock knows what time zone you’re on. As a matter of fact, my first work as a postdoctoral fellow was with Dr. Czeisler studying blind people. We wanted to know, did they still have body clocks? And it turns out, by every criteria, hormones, performance, alertness, sleep, they all had fully functioning body clocks, but their body clock didn’t necessarily know what time of day it was outside.
So some of them were what’s called free-running, because they didn’t have light input, and the clock is not exactly 24 hours. Some of them were drifting like 15 to 20 minutes later every day. Sometimes they were able to sleep at night when their body clock was aligned with the outside world. Sometimes they had problems sleeping at night, and they took lots of naps, because now their body clock was no longer aligned. And then around a month or so later, they’d be back in sync again.
The other important thing about the blind people is that we discovered that there’s a different photoreceptor in the eye, and we showed it in humans before it was shown in animals. So this was work with Dr. Czeisler. And for so many years, we’ve only focused on rods and cones. That’s what’s needed for conscious vision.
It turns out there’s a different photoreceptor in the eye called intrinsically photosensitive retinal ganglion cells. And we found some blind people who had no conscious vision but still had light input to the body clock, and we could effectively shift their body clock or suppress hormone levels. So this was published in the New England Journal of Medicine, and Dr. Czeisler is the first author, because we could show that there was a whole new photoreceptive system.
Just like your ear processes both hearing and balance, your eye processes both conscious vision and this different photoreceptive system that’s important for circadian rhythms, for some hormones, for some of your heart rate, your mood, and other things. In the past 25 to 30 years, we’re still learning lots of really exciting things about basic human physiology.
Ivelisse Estrada:
So why don’t we shift to talk about the work that you’ve done with your colleagues on daylight saving time?
Elizabeth B. Klerman:
The Radcliffe Institute provided a safe environment and funds and support staff, that we could invite everybody in here and have a frank discussion. We also had members of the government who otherwise would not have been able to come, who could nonetheless give us very valuable insight into how government policy is made—such as the Sunshine Protection Act, such as the Congressional Research Service writing a report, the Department of Transportation’s role in daylight saving time, the different safety areas of the government—so how all these different areas of the government were involved in public policy that, in turn, affects all of us.
And then we brought in scientists and economists and energy specialists and people from the business world to talk about their research on that, and we could also talk messaging, both for the government and for the public.
I’d also like to talk about the science behind daylight savings time.
Ivelisse Estrada:
Yes.
Elizabeth B. Klerman:
The Radcliffe Institute was just so instrumental in pulling and helping us bring all of these people together to talk about, “Well, what can we do if science is not enough?” The vast majority of scientists say that daylight savings time is not good for our health. And we also learned at the Radcliffe Institute, it doesn’t necessarily save energy. It’s not good for learning for children. And daylight saving time was originally brought in because it was supposed to have energy savings. That hasn’t been shown, and I learned at the Radcliffe Institute that it also is not causing benefits in these other areas.
Ivelisse Estrada:
I learned that we can thank Benjamin Franklin for this concept. He posed it in a satirical piece that he wrote, suggesting that it would save money on candles. [Laughs.]
Elizabeth B. Klerman:
So one of the issues about saving of energy—and once again, I am not an energy specialist, I’ve just also done some research—is that life has changed a lot since Benjamin Franklin’s time. And it’s my understanding that the energy costs related to heating and cooling overwhelm any other difference. At the congressional hearing a year and a half ago, a representative from Arizona said, “Please don’t make us change our clocks.” And indeed, Arizona does not change between standard time and daylight saving time. They said, “It’s hot enough during the clock hours when people have to be out. If we switch the clock hours so they have to be outside, our energy and health outcomes will be even worse.”
Heather Min:
Where the heck did daylight savings time come... Because I’m assuming this is a more recent phenomenon than us having synchronized watches and clocks.
Ivelisse Estrada:
I actually know the answer to this.
Elizabeth B. Klerman:
Okay, please.
Ivelisse Estrada:
It was first instituted in 1918 as a wartime measure during World War I. It lasted for seven months then. Then it was brought back during World War II, where it was permanent daylight saving time during the war. Daylight saving time was then instituted in the early ’70s, I think: ’74.
Elizabeth B. Klerman:
So the switch between standard and daylight?
Ivelisse Estrada:
Yes. Yes, the switch. Yes.
Heather Min:
Fairly recently.
Elizabeth B. Klerman:
But daylight saving time has been tried before, and they always—it’s also been tried in Great Britain and in Russia, and it’s always ended because of unpopularity.
Ivelisse Estrada:
Yes.
Elizabeth B. Klerman:
That’s when it happened. Once again, I don’t know all the politics behind why it’s been done. Some reasons have been given, have been related to energy. The Sunshine Protection Act, which was published a few years ago, the arguments were given that, “I like more sunshine in the afternoon. I want to be able to come home from work and play ball with my kid outside, or I want to play golf or something like that, that I want ‘more sunlight.’”
Well, you don’t get more sunlight. The number of hours of sunlight remain the same. The question is just whether they’re in the morning or in the afternoon. Some of the arguments against it are that means it’s dark in the morning when kids are going to school. During the ’70s, when it was instituted, there was an increase in accidents in Florida of kids waiting for the school bus.
So you have to think about who’s now going to school in the dark, because you’ve changed the clocks, versus how much light you have in the evening. So that’s the Sunshine Protection Act argument, “I want more light in the evening, because after I get home from work, I want to be outside.” That’s one of the arguments. That’s a different argument than why it was originally done.
Ivelisse Estrada:
So let’s talk about the health implications.
Elizabeth B. Klerman:
So there’s two parts about the switch between daylight saving time and standard time. One is the time of the switch, and the other is what happens when you’re on daylight saving time for a couple months a year. So let’s start with the time of the switch. In the spring, when you switch, you, quote, unquote, “lose an hour of sleep,” because you’ve sprung ahead, and the combination of the change in the clocks and the reduced amount of sleep is associated with more car accidents, more heart attacks, many negative physical findings.
In the fall, when you get an extra hour, there’s once again a switch. And there are not as many changes, and it could be because you’re doing a switch and people are getting an extra hour of sleep—which, hopefully, I’ve convinced you, most people don’t get enough sleep—and the extra hour of sleep will make a difference. So in terms of the immediate switch, it’s dangerous for people on physiological and safety reasons.
Heather Min:
Even though it’s just one hour.
Elizabeth B. Klerman:
Even though it’s just one hour. There are many studies that show, in those first few days, there’s increased heart attacks, increased cardiovascular outcomes.
Heather Min:
Can’t we all just drink more coffee?
Ivelisse Estrada:
[Laughs]
Elizabeth B. Klerman:
Well, coffee makes you feel alert. It doesn’t necessarily help your heart function or all sorts of other things like that. The second point is what happens in the long term. So, two things. First of all, since, hopefully, I’ve convinced you that light exposure through the eye is what your body clock knows what time of day it is, there’s fairly good evidence that your body does not totally adjust to daylight saving time.
So your body does not fully switch to the new, quote, unquote, “time zone,” because it’s still getting light. And you are also getting more light at night because you’re up at the night, both outside and with light, because you’ve turned on the lights at night to do whatever you’re going to do. Okay. Light at night makes your body think you should stay up later.
Just think about jet lag, flying from here in Boston to California. Your body gets light later, because if you’ve done an evening flight, your body goes, “Oh, it’s light out. I need to shift to go later.” Now you’re doing that every night that daylight saving time is on. It will help shift your body a bit later, but the alarm clock still goes off the same time. So people are getting less sleep.
Ivelisse Estrada:
One thing that I thought was interesting from the report that I read from the seminar is that there were higher incidences of cancer as a result of daylight saving time. What is that about? How does that work?
Elizabeth B. Klerman:
So that’s not exactly as a result of daylight saving time. It’s your question about, “Does one hour make a difference?”
Ivelisse Estrada:
Okay.
Elizabeth B. Klerman:
So we can’t really do a test about daylight saving time versus not daylight saving time most of the time. For energy, there were such tests. Australia, I believe it was, when they hosted the Olympics, they delayed switching clocks. And so, you could compare energy before and after, and it was shown there was no energy savings.
Another way of doing it is, since we can’t usually do a trial with and without, is to look at within a time zone, because if you think about a time zone, it’s one hour from the eastern edge to the western edge, or it should be. If you actually look at the United States, it jiggles a little because of where state boundaries are, but it should be one hour. And so, we can look and say, “Well, does one hour make a difference in terms of something that happens on the eastern side versus the western side of a time zone?” Because that’s a one-hour difference, even though it’s only one hour. It’s an excellent question, and people ask it.
And so, the answer is, yes, it makes a difference. The people on the western edge of a time zone have more of certain types of cancers, have more diabetes. And when we talk about car accidents during the daylight saving time change in the spring, there’s more car accidents on the western side than the eastern side of the time zone. So we know from great studies done by economists, if you look at the western versus the eastern part of the time zone—and because for some states, it’s even more than an hour because of the state boundary, it just gets worse. So we do know that sometimes just one hour makes a difference.
Heather Min:
And as to why people are still trying to figure that out?
Elizabeth B. Klerman:
So one of the things that I learned at the Radcliffe seminar is the importance of messaging, and scientists are not necessarily good at messaging. We had somebody from the legislative branch who said, “Well, I can always find somebody who tells me daylight saving time is good. But you scientists say, ‘Well, we don’t know. We need some more evidence. There’s this, there’s that.’”
Scientists need to learn to broadcast a single message better than we’re used to doing. The example that was given me was that there was never a randomized control trial of the effects of cigarette smoking. There was just so much evidence that cigarette smoking was bad that laws were changed, and public opinion was changed. Though it’s very interesting, public opinion apparently didn’t change until secondhand smoke was discovered.
Ivelisse Estrada:
Right. You’re making a choice versus—
Elizabeth B. Klerman:
You’re affecting somebody else.
Ivelisse Estrada:
Yeah.
Elizabeth B. Klerman:
So scientists need to learn to have a message, even if we don’t have all the answers. And that was one of the things that we worked on with Dr. Robbins, who is a phenomenal person in health messaging, and tried to work on how scientists could unify our message, at least to the public—without lying to the public, but making it clearer.
So one of the examples I also give is the polling about daylight saving time versus standard time. Polling is frequently asking people about summertime versus wintertime. I think if you asked a question the way my colleague in Seattle asked about, “How many days do you want your child going to school in the dark?” you might get a different answer. Right?
If you ask most people, “Do you want summertime versus wintertime?” they’re going to say summertime. So some of it is also learning how to ask a question to get a result that is consistent or helps us educate the public, because we do need to educate the public better about daylight saving time.
Ivelisse Estrada:
And we should say where the Sunshine Protection Act stands now, which is that it passed the Senate, but then it was stopped by the House pending more research.
Elizabeth B. Klerman:
So it’s actually interesting. The time was actually the reverse.
Ivelisse Estrada:
Oh!
Elizabeth B. Klerman:
So the House had hearings and said, “We don’t have enough information.”
Ivelisse Estrada:
Okay.
Elizabeth B. Klerman:
And then the Senate passed it on a voice vote without discussion.
Ivelisse Estrada:
Oh.
Heather Min:
And the Sunshine Protection Act, it’s to institute daylight savings time as a permanent—
Elizabeth B. Klerman:
Yes. Year-round.
Heather Min:
…clock shift.
Elizabeth B. Klerman:
Boston would now be on Atlantic time. Chicago would now be on what’s called the East Coast time.
Heather Min:
Everybody is just—
Elizabeth B. Klerman:
Colorado would—
Heather Min:
…one hour ahead.
Elizabeth B. Klerman:
One hour ahead, but the sun wouldn’t have changed.
Heather Min:
And yet, you have obviously persuaded me, anyway, that one hour does make a difference.
Elizabeth B. Klerman:
Yes. And the other part that we haven’t even brought up is disparities. So this would mostly affect people who don’t get enough sleep already. And you can think about people who have to work two or more shifts, or those people who are up to get you your 4 AM coffee at a particular coffee place or at the airport. Those tend to be people of lower socioeconomic status and different race and ethnic backgrounds, and this would contribute to their potentially getting even less sleep.
Ivelisse Estrada:
And these are people who already have health disparities as a result of their—
Elizabeth B. Klerman:
Already have health disparities.
Ivelisse Estrada:
Yup.
Elizabeth B. Klerman:
Yes. And I want to thank Karin Johnson of UMass Worcester for bringing that to my attention. She’s done a lot of work on that.
Heather Min:
Can we jump to what you do as a sleep researcher? What are the tools of your trade?
Elizabeth B. Klerman:
I spent the first 25 years of my career at the Brigham and Women’s Hospital, where Dr. Czeisler, who coled the first Radcliffe symposium, he has established a facility there that is basically unequaled in the world, where we can do these kinds of sleep and circadian rhythms experiments with highly skilled nurses and support staff, with support of NIH and other funders. And the rooms have no windows so that we can manipulate somebody’s schedule and put them on a non-24-hour day or put them on Japan time or do something like that.
And there, Dr. Czeisler—and many people he has trained and with whom he has worked—has done a huge amount of work to identify the importance of both sleep and circadian rhythms and their interaction on human physiology in terms of alertness or sleep or hormone levels, on the effects of caffeine when you take caffeine in the morning or something like that.
And then I moved to Mass General to bring sleep and circadian rhythms to the rest of medicine. So rather than concentrating mostly on healthy older or younger people, what is the effect of sleep and circadian rhythms on people with a neurologic disease like Alzheimer’s or Parkinson’s disease? What happens in children with Down syndrome? What happens in people with neurofibromatosis, people with sleep disorders?
Well, I’ve also worked with the Gun Violence Prevention group. I’m working with somebody at UMass on smoking cessation, susceptibility to smoking in adolescents. I’m having so much fun, because I’m learning about what so many people do, and I’m just saying, “Have you thought about how much sleep somebody got the night before? Does that affect their pain? Does that affect their response to a drug?”
I don’t do just one thing anymore. I view myself more as trying to increase education about including sleep and circadian rhythms as part of studies of normal physiology, as part of studies of disease processes in terms of, “Does it affect the disease process going into it if you have not enough sleep or if you work shift work? What does that do to the actual disease process itself?” to “Does it make a difference what time of day you intervene?” And it’s part of the greater move in the field towards what’s called circadian medicine or chronomedicine, where we want to think about it.
Heather Min:
So why don’t you educate us on, are there better kinds of brain activity?
Elizabeth B. Klerman:
So there are different kinds of brain activity.
Heather Min:
Are some better than others?
Elizabeth B. Klerman:
When we measure sleep using, what I said, that polysomnogram, where we look at people’s brain waves and eye movements and chin movements, sleep is usually divided into rapid eye movement sleep, which is what it sounds like. Your eyes are moving rapidly, and sometimes you see muscle twitches. Overall, during rapid eye movement sleep, you’re actually paralyzed. You don’t move a lot, but you can have muscle twitches, the proverbial, “Oh, my dog must be chasing a rabbit or something.”
And when you wake up somebody from rapid eye movement sleep, or REM sleep, they’re more likely to report they’re having a dream. The other stages of sleep are called non–rapid eye movement sleep, or non-REM sleep. And there’s currently three stages of non-REM sleep. One is, if you wake somebody out of non-REM sleep, they’ll tell you they weren’t asleep, but they have decreased reactivity to stimuli. It’s why, I think, there are rumble strips on the road, because you can drive in stage 1 sleep.
Heather Min:
Wow.
Elizabeth B. Klerman:
So you wake somebody out of non-REM stage 1, and they go, “I wasn’t asleep.” Stage 2 sleep is a slightly deeper stage of sleep, and where it’s harder to wake up somebody. And it has certain specific things in the EEG called spindles and K-waves, because they look like Ks. And stage 3 is the really deep sleep. You tend to have more of it at night. You’re much more difficult to wake up. Different things happen during different stages of sleep. Bob Stickgold, who’s a phenomenal researcher in learning and memory, has shown that different parts of learning and memory occur preferentially if you have certain amounts of different stages of sleep.
Ivelisse Estrada:
It’s my understanding that you need all those stages of sleep, and they work holistically to help you function—
Elizabeth B. Klerman:
Function during the day. Right. Because during the day, you’re doing—
Ivelisse Estrada:
…at your highest level.
Elizabeth B. Klerman:
Right. And that’s the first step we say, is give yourself enough time to sleep, and you shouldn’t need an alarm clock. Till Roenneberg compares it to a washing machine: Would you stop a washing machine early? No. “The clothes look clean. I’m going to stop the washing machine.” So why should you stop sleep early because you think you’ve had enough? For many people, they just don’t give themselves enough time to sleep. I realize that for some people, they don’t have enough time because they have family or work or other obligations.
Now, if you’ve been in bed for eight-plus hours, and you’re still tired for many days, from at least three or four days, and you’re still tired, or your bed partner complains about snoring, or even is no longer a bed partner because you snore so much or you wake up gasping, or if your bed partner complains that you kick a lot, you may have a sleep disorder, and you should go see a sleep clinician, because sleep disorders can be treated. And you want to treat sleep disorders. There are also the sleep disorders you’ve heard about, mostly in kids called parasomnias, like sleepwalking and sleep talking. And some of those can be also taken care of.
Ivelisse Estrada:
Let’s talk about sleep hygiene.
Elizabeth B. Klerman:
Let’s call it sleep education instead of sleep hygiene.
Ivelisse Estrada:
Yes. Okay. [Laughs]
Elizabeth B. Klerman:
When I put my kids to bed, and other people I know, you told them, “It’s time to get ready for bed.” You put them in their pajamas, you read them a story, and then they went to bed. They didn’t watch a horror movie and then climb into bed. They didn’t pay bills and then climb into bed. Their body sort of had a time to think, “Oh, it’s time to go to bed.” And there was a fairly consistent bedtime.
So if people are having problems with sleep, the recommendations are usually: Don’t do something really stimulating just before you go to sleep. Don’t watch a horror movie. Don’t do something… Tell your body, give your body a little time to relax and figure out it’s time to start going to sleep, and trying to have a fairly regular bedtime and wake time. Those are the things that we usually suggest.
If you’re having problems sleeping, no coffee with dinner. Maybe not even coffee after 2 o’clock in the afternoon. Alcohol helps you fall asleep but then disrupts your sleep once you’re asleep. I know that lots of people use it to fall asleep. Some of this also depends on whether or not you complain that you’re having problems sleeping.
So insomnia is a real problem for many people, and it’s become interesting that for some people, insomnia may indeed be related to the timing at which they go to sleep. So if you’re a night owl, and you climb into bed at 11, because you have to wake up at 7, you might have problems falling asleep, because your body clock really wants you to be awake later and sleep in later.
And if you’re really an early-ish person, and you really want to go to bed at 9 o’clock, but you want to be social, and you go to bed at 11, but your body wakes you up at 4 o’clock, 5 o’clock in the morning, some of that insomnia may be related to a body clock issue, timing of sleeping, and some of it may be a different kind of insomnia. So there are many kinds of insomnia. From the circadian perspective, some of them may be related to when you’re trying to sleep versus when your body clock wants to be asleep, almost as if you have jet lag in the time zone you’re in.
Ivelisse Estrada:
So that’s my problem, perpetual jet lag. No. [Laughs.]
Heather Min:
Well, can I ask a random question? I’m wondering about white noise and why that’s effective.
Elizabeth B. Klerman:
That’s a great question. I don’t know, and I’m actually asked that a lot. And the studies that I usually know are about the detrimental effects of noise on sleep. So what if you live near a highway, or you live near an airport? And which, once again, has disparities issues? I don’t know of studies, and there indeed may be studies about white noise. I just don’t know it. We usually suggest that people not have a TV in the background or whatever, but there are clearly people who say that it helps them. I just don’t know the answer to that.
Ivelisse Estrada:
What is melatonin?
Elizabeth B. Klerman:
So melatonin is a hormone secreted by the pineal gland in mammals. Its nickname is the Dracula hormone, because its levels are low during the day, high at night, and can be suppressed. Their levels go down by light exposure at night. Indeed, melatonin is how we showed in those blind people that some of the blind people still had light input to their biological clock, because the pathway from the outside world, through the eyes, to the pineal gland goes through the biological clock.
And when we found some blind people in whom we could suppress melatonin, it meant that light was still reaching the biological clock. It is a great marker that we use for experiments of the internal biological clock, because there is a pathway from the biological clock to the pineal gland, and it is relatively not affected by eating or sleeping or posture changes. You just need to do this study in dim light, because it’s affected by light.
It’s a hormone. It’s part of your natural biology. Now, not all of natural biology is healthy. There are poisonous mushrooms. And why some European countries ban it? I don’t know. I know certainly within the United States, there is worry that what you get in a bottle in a health food store is not necessarily what you’re expecting in terms of two things. The first question is, how pure is it? In other words, is what’s in the bottle only melatonin and nothing else?
And the second question is, is the dose that’s on the outside of the bottle the dose of what’s inside the bottle? And the New York Times, a couple months ago, had an article where somebody looked at gummy bears and found a huge percentage of the gummy bears that had melatonin did not have the amount of melatonin that they said they did. There was less, or there was more.
So when people ask me about taking melatonin, the first thing I say is, “I don’t know where you can get it, where it is pure and the potency that you think it is.” So that’s the first thing I say. And so, I can’t necessarily recommend it. The second issue is, why are you taking melatonin? And some people take it because they want to go to sleep. They think it kind of helps to go to sleep. And it is indeed true that melatonin rising in the evening is associated with your getting tired. Correlation, not necessarily causation, that the body clock says, “It’s about time to start going to sleep,” and melatonin is the biological marker.”
Multiple studies have shown that if you give melatonin when somebody is usually going to sleep, it does not necessarily help their sleep. Melatonin appears to act by quieting the wake-up signal from the body clock. And so, it works if you’re trying to sleep when you wouldn’t sleep, like jet lag, but it doesn’t necessarily work if you’re trying to sleep at your usual time.
Now, I don’t want to get people upset that’s saying, “I take melatonin, and it works for me.” I don’t know when it works for some people and when it doesn’t. All I know are the studies that I’ve read, that that’s how melatonin works. We’re currently doing a study at the Brigham and Women’s Hospital looking at melatonin in pregnant women, where we showed this in association between the amount of melatonin in women’s blood or saliva and the number of contractions they have in late-term pregnancy.
And this was brought to our attention by somebody who’d done a study that showed that melatonin receptors appear on women’s uteri, uteruses, late in pregnancy. If you look at uterine tissue in a test tube, and you drip melatonin on it, the uterine tissue will contract. So now we have a mechanism. Melatonin’s high at night. Melatonin causes contractions. The melatonin receptors don’t appear until late in pregnancy, when maybe the uterus is ready and then babies would be born.
So we did a first round of study, supported actually by the Harvard Milton Fund, where we looked at red light, which doesn’t suppress melatonin, and blue light, which suppresses melatonin, and looked at the number of contractions that late-term pregnant women had, like 38 weeks. And we showed that the amount of melatonin was correlated with the number of contractions. The more melatonin, the more contractions. Right now, we’re doing a study funded by NIH, where we’re giving melatonin to see if we can change the number of contractions.
To me, as a biological circadian rhythms person is, what if nurse-midwives were right, and you should give birth in a dark room? Right? What if we should change the lighting levels in hospital areas? And that’s one of our goals. Once we can show on a more mechanistic level about melatonin levels, placebo versus not, in daytime and nighttime, we will probably go back and see if we can do a study about changing lighting levels and see if labor is even a little bit shorter, which would be nice in terms of women’s comfort, in terms of medications given, in terms of babies, and in terms of the hospital resources.
Ivelisse Estrada:
This is really fascinating. How do you feel about sleep?
Elizabeth B. Klerman:
I love sleep.
Ivelisse Estrada:
Me, too.
Elizabeth B. Klerman:
It’s an important part of my day, I guess you could say.
Ivelisse Estrada:
In many ways.
Elizabeth B. Klerman:
In many ways. Yes.
Heather Min:
Well, I always knew I loved sleep like the both of you—but, wow, so much more to think about. One hour makes all the difference.
Ivelisse Estrada:
Thank you so much.
Elizabeth B. Klerman:
Thank you both for your interest in the work of myself and many, many other scientists and clinicians and researchers.
Heather Min:
That concludes today’s program. Thank you for joining us.
Ivelisse Estrada:
BornCurious is brought to you by Harvard Radcliffe Institute. Our producer is Alan Grazioso. Jeff Hayash is the man behind the microphone. Anna Soong provided editing and production support.
Heather Min:
Many thanks to Jane Huber for editorial support, and we are your cohosts. I’m Heather Min.
Ivelisse Estrada:
And I’m Ivelisse Estrada. Our website, where you can listen to all our episodes, is radcliffe.harvard.edu/borncurious. If you have feedback, you can email us at info@radcliffe.harvard.edu. You can follow Harvard Radcliffe Institute on Facebook, Instagram, LinkedIn, and X. And as always, you can find BornCurious wherever you listen to podcasts.
Heather Min:
Thanks for joining us. We’ll see you next time.
