3 Takeaways - Three Science-Backed Changes That Will Help You Sleep Better - Starting Tonight (#278)

Episode Date: December 2, 2025

Sleep shapes your mood, memory, immune system, and long-term health, yet most of us aren’t getting enough. Harvard Medical School sleep scientist Dr. Elizabeth Klerman shares the three easiest science-backed changes proven to improve your sleep tonight, plus the myths that make things worse. If you’re struggling to fall asleep, waking at 3 a.m., or dragging through the day, this episode is for you. 

Sleep shapes our energy, our mood, our focus, and even how we age. And the science shows that small, simple changes can make a big difference. What does the science say will help us sleep better and feel better? Hi, everyone. I'm Lynn Toman, and this is three takeaways. On three takeaways, I talk with some of the world's best thinkers. business leaders, writers, politicians, newsmakers, and scientists. Each episode ends with three key takeaways to help us, understand the world, and maybe even ourselves, a little better.

Today, I'm excited to be with Dr. Elizabeth Clermann, one of the world's leading sleep scientists and a professor at Harvard Medical School and Massachusetts General Hospital. She spent her career studying how sleep affects our health, our mood, our memory, and even how we age. She also studies what we can do to improve our sleep. Welcome, Beth, and thanks so much for joining three takeaways today. Thank you, Lynn, for asking me to join you. I'm looking forward to our conversation. Me too, and thank you.

Beth, you're one of the world's leading sleep scientists. Let's start with the most basic question that people want to know. How much sleep do we really need? The answer depends on the individual. And even within that individual, it depends on whether or not they're sick or not. The usual advice I give is that if you need an alarm clock to wake up, you're not getting enough sleep. For some people, that might be five or six hours of sleep. But that's very, very, very rare.

and as a matter of fact, a group of scientists at the University of California, San Francisco are studying people who only need that much sleep. For most people, it's probably in bed time, approximately seven and a half to nine and a half hours in order to get seven to nine hours of sleep because most people don't climb into bed and immediately fall asleep and wake up and bound out of bed unless, of course, you have a child waking you up. what's happening in our brains and bodies when we chronically under sleep and why is it so harmful? We know from sleep deprivation experiments that basically every physiologic function is affected if you don't get enough sleep.

Cognition, mood, think about a cranky three-year-old, immune function, you know, you're more likely to get sick, you don't respond as well to a vaccine, cardiovascular function, blood pressure, shift workers and other people who get insufficient sleep may have high. blood pressure, lung function, you know, kidney function, everything, basically everything we know is affected by insufficient sleep. What's a common myth about sleep that simply isn't true? That you can get away with less sleep than you are right now. There's no evidence that you can train yourself to sleep on less than you body clock wants you to do and you don't do well if you don't get all to sleep your body needs. That's the myth I'd like to counter. Insomnia seems to be everywhere. What's actually happening biologically when someone either can't fall asleep or can't stay asleep? Asking about insomnia is a great question and the answer is complicated because actually there's many different kinds of insomnia all with the same symptom, which is you can't fall asleep, but there's multiple possibilities of why people can't fall asleep. Some of them can be changed by patterns. For example,

don't have coffee before you go to sleep, alcohol helps you fall asleep, but then disturbs your sleep in the middle of the night. So some insomnias are caused by behaviors. Some of the insomnias are probably caused by a mismatch between the person's internal biological time, their circadian rhythms, and the outside world. So if you are a teenager, your body clock is naturally later. You're a late type. You want to stay awake late. and if somebody put you in bed at 10 o'clock at night, you would have insomnia at the beginning of the night because your body clock doesn't think it's time for you to sleep, sort of like what happens if you flew across time zones and your body clock hasn't caught up with

the new time zone. So some insomniaers are related to whether your body clock thinks it's too early for you to go to sleep or thinks it's too late for you go to sleep. So there are also very early types who really want to go to sleep at like 8 or 9 o'clock at night. And those people tend to stay awake late because they feel like otherwise they're missing the party or they're being antisocial or their partner says, why aren't you joining us even though they're tired? But then their body clock tries to wake them up like at three or four o'clock in the morning. And so they now have not sleep onset insomnia, but they wake up too early type insomnia and they can't fall back asleep.

And so there are other insomnias that may also sort of be learned in insomnia's than cognitive behavioral therapy is great for insomnia. So once again, it's this one symptom with many different causes. We would encourage you to talk to a professional to figure out which exactly is the cause so that we can target the treatment to the actual cause. For people with insomnia, for those that either have trouble falling asleep or have trouble staying asleep, what are the most effective science-backed interventions? What genuinely works?

We usually tell people to start with what's called sleep hygiene, which I hate the word hygiene because it makes it sound like something's dirty. But anyway, let's talk about good sleep practices, which is sleep in a cool room, don't have caffeine or alcohol for hours before you go to bed. Don't pay bills or watch a horror movie before you go to bed. If you have kids and your kids had a bedtime routine, there was after dinner, and then there was a bath, and then you read them a story. and their body's learned to sort of associate this pattern to go to sleep, and you can teach your body to do the same thing. Those are the sleep hygiene type suggestions. No bright screens before you go to sleep.

Bright screens tell your body it's time to be alert and wake up. The body clock is especially attuned to blue wavelength lights. You may have heard that get blue blocking screens, but even so, the suggestion is not to use bright screens. if you're going to read a book, try and do it on paper instead of screens. So those are all behavioral things. There are things for which medication might be useful. So if you're trying to change the time of somebody's biological clock,

you might use melatonin to help somebody sleep and change the timing of light. For very late people, you might choose melatonin to try and have them fall asleep at night and give them light in the morning to shift their body clock earlier. we don't recommend melatonin for people who are trying to go to sleep at the time at which their biological clock thinks they should go to sleep. Melatonin is the hormone of darkness. It's when your body says it's time to go to sleep. So if your body already thinks it's time if you go to sleep, melatonin will probably not work. And then there's cognitive behavioral therapy, which is not a medication. There are some cognitive behavioral therapies available online if you cannot find a clinician to help you do it.

Once again, all of those depend on the reason why you're having insomnia. Talking about people who wake up in the middle of the night or wake up too early in the morning, what are some of the most effective science-backed interventions? Cognob behavioral therapy has techniques for people with insomnia. It's one big intervention that has multiple components to it that includes understanding people's perceptions and misperceptions about sleep and sleep duration. It includes behavioral changes that occur over time. And so it's a multi-week month process.

Let's zoom out. What is the brain actually doing while we sleep? And why isn't just resting enough? Different parts of the brain are doing different things when we're asleep. Lots of things are happening in the brain. The neurons are behaving differently. There's different firing patterns of different neurons and different parts the brain. For example, there are some evidence that in some areas of the brain, the brain is

sort of replaying what happened during the day as part of memory consolidation. Also, similar to what are called the lymphatics in the rest of the body, there's lymphatics that when people are asleep, they open up a little more and waste particles can go out. Some reprogramming is happening. Synaptic pruning. So synapses are sort of the connections between neurons. as you could say. And pruning of that happens. You don't remember everything that happened today. And you don't want your brain to sort of be cluttered with everything that's happened over all the years of your life. Some of those things are pruned and no longer remembered. So things you might remember at the end of the day, you're not going to remember in a few days. Lots and lots of things

are happening at multiple levels in the brain during sleep. You study circadium rhythms, our internal clocks. How powerful are these clocks? And what happens when we constantly fight them by staying up too late or getting up too early. Circadian rhythms are this internal clock that the central pacemaker is in your brain. It actually sits just above the optic chasm where light travels from the eye into the brain because it gets light input from the brain. It in turn affects just about every other known physiology that we have. It affects when you feel alert and when you feel tired.

It affects how well you perform on a test and when you go to sleep. It affects your heart rate, your mood, your gastrointestinal function. It affects just about everything. And in addition, we now know there are also peripheral circadian clocks. You have a clock in your liver. You have a clock in your heart. You have a clock in your kidney. The central clerk influences those.

They can't be influenced by light because they have no way of getting light information directly. they in turn are influenced by other things probably like eating and fasting. What happens when they're misaligned? Well, if you've ever had jet lag, you know what happens when your internal circadian clock is different than the outside world or for people who work shift work. You're tired when you want to be awake. You're awake when you want to be tired. You may have headaches.

You may be irritable. You may have stomach upset. All of these things are because you're trying to do something when your internal body clock doesn't think it's time to do it. And so the hormones aren't ramped up or the gastrointestinal is not ramped up or your brain thinks it should be asleep and it's not functioning very well. So circadian rhythms influence sleep. Sleep is the most obvious output of circadian rhythms and circadian rhythms also affect just

about every area of physiology. Can you walk us through sleep architecture? What are rapid eye movement, so-called REM sleep and deep sleep. and what do they actually do for us? Rapid eye movement sleep is when most people say that dreams occur. It's when if you look at somebody, they have rapid eye movements, even though the rest of their body is not moving. Deep sleep is from non-rapid eye movement sleep,

and it's when people sleep very deeply. You alternate between non-REM sleep and REM sleep across the night. Different things happen during REM sleep and non-REM sleep. So both are important. Is there anything we can do to increase our REM sleep and our deep sleep, or are those stages mostly beyond our control? The stages of deep sleep and REM sleep are mostly beyond your control. There is some evidence if you stay awake longer, you will have more deep sleep, but I don't

want you to stay awake longer. If you sleep at a different time of day, you may have more REM sleep, but then you're not sleeping at the time of day that we want you to sleep. So the answer is, please don't try and change the relative amounts of non-REM and REM sleep under boss conditions. We now live in a world where you can work, scroll, or stream at any hour. How is the 24-7 lifestyle changed our relationship with sleep? Unfortunately, the 24-7 lifestyle means that most people are not getting enough sleep. Whether they don't have a choice because they need to work at night for their work or because they're staying away.

because they want to stay awake. There was an interesting book written called At Days Close, where if you go back and look at Shakespeare and the Bible and a number of older books, people used to go to sleep when it was dark and wake up when it was light because they couldn't afford candles or other things, in which case people slept more than they do now. And actually sometimes they slept and then they were awake a little in the middle of the night and then they slept again.

But all the evidence is that as the world has become more industrial, we are sleeping less and less, but our body does not change as quickly. You need to spend more time sleeping. If listeners could change just three things tonight to dramatically improve their sleep, what should they do? They should not have caffeine or alcohol for a few hours before they go to bed. They should try and relax starting around a half hour to an hour before they go to sleep. and they should try and sleep in a cool, dark room.

And the fourth one is give yourself time to go to sleep. So I went up to four. You're going to have to forgive me. That is just fine. Before I ask you for the three takeaways you'd like to leave the audience with today, is there anything else that you wish people understood about sleep that we have not covered? I want to talk about what happens when you're awake when your body and your brain think you should be asleep. I realize that some people are awake at night when they want to be asleep because they're in pain or because they have insomnia or because they're a policeman walking a beat or doing their work.

But the brain at times at which the circadian clock and how long you've been awake wants your brain to be asleep does not function as well as it does during the day. You have delayed reaction time. You're more likely to make risky decisions. you're less likely to sort of change your mind, even if you're confronted with evidence that you're wrong. You're more likely to remember negative things rather than positive things. So it's not a good time of day to be awake in terms of functioning and making decisions. And so once again, if you can be asleep at the time of which your body clock wants you to be

asleep, it's good also in terms of your brain and your behaviors. Beth, what are the three takeaways you'd like to leave the audience with today? Number one, give yourself enough time for sleep if you can. I realize that some people can't because they have family or work obligations. However, many people do have time. Plan to try to be in bed at least eight hours of sleep and help yourself prepare for that sleep. And it will be good for your brain and for your rest of your body and for your performance. and people around you might also be happy.

Number two, insufficient or disturbed sleep is associated with health and safety problems, cardiovascular problems such as blood pressure, metabolic problems such as diabetes are being overweight, immune function getting sick or vaccines or mood is psychiatric problems. All of these problems are associated with insufficient or disturbed sleep. A third takeaway is that sleep disorders exist. I've already talked about having insomnia, which is when you can't sleep when you want to. There's also sleep disorder breathing or obstructive sleep apnea where people snore very loudly or stop breathing during sleep.

That should definitely be treated. There's restless legs when people kick a lot during sleep or if people act out their dreams or if they're really very tired still after being in bed for eight hours for multiple times. In all of those cases, please consult a clinician. Beth, thank you so much for joining three takeaways today. And thank you for your research on sleep to help all of us sleep better and feel better. Thank you very much for your interest in our work. If you're enjoying the podcast, and I really hope you are,

please review us on Apple Podcasts or Spotify or wherever you get your podcasts. It really helps get the word out. If you're interested, you can also sign up for the Three Takeaways, newsletter at three takeaways.com, where you can also listen to previous episodes. You can also follow us on LinkedIn, X, Instagram, and Facebook. I'm Lynn Toman, and this is Three Takeaways. Thanks for listening.