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Why Sleep Matters | Matthew Walker | Talks at Google

Sleep is one of the most important aspects of our life, health and longevity and yet it is increasingly neglected in twenty-first-century society, with devastating consequences: every major disease in the developed world - Alzheimer's…

Matt BrittinhostMatthew Walkerguest
Jul 12, 201956mWatch on YouTube

Summaries, chapters, transcripts, and FAQs on this page are made by uListen, not YouTube.

Transcript

  1. 0:00 – 0:06

    Intro

    1. MB

      [upbeat jingle]

  2. 0:06 – 3:10

    Sleep reality check: seven hours or less is impairment for everyone

    1. MB

      Hello, everybody. [cheering] Happy Monday. [cheering] Yeah, hmm, kind of. [laughing] Have you ever read a book and been, like, on a mission to get other people to read that book? Like The Great Gatsby or what books were you, you on a mission to get people to read? This one. This one? [laughing] Yeah, this one. No, seriously. Seriously. Me too, actually. So a few years ago, I read some research about sleep and, um, it changed how I thought about sleeping, particularly for somebody who does lots of travel, sleeping in hotel rooms, and has jet lag. It really changed my life for the better. And then I read this book, uh, as-- w- and the point it came out last year, and I've been giving it to people, recommending it to people, et cetera, so I couldn't be more excited about today. Before we get up, its author, our legendary guest speaker and sleep diplomat, Matt Walker, I just wanna ask you a couple of questions. So have a think, how much sleep did you get last night? How many hours sleep did you get last night? Just have a think, figure it out. Okay, so how many people got between five and six hours sleep last night? Ooh, that's about twenty people or so. What about six to seven hours sleep? Oh, about a third of the people maybe. Seven to eight? Yeah [laughing] Maybe, yeah. Eight to nine? [laughing] Anybody got more than, more than nine hours sleep? Yes! [laughing] Congratulations. Anybody have young children? You probably need to leave the room at this point. Okay. [laughing] Time to get on with, with the show. So Matt Walker is the professor of neuroscience and psychology at UC Berkeley on the West Coast. He founded the Center for Human Sleep Science. His work has focused through his life on understanding the role of sleep in health and in diseases, and he's published over a hundred research studies. He's Liverpool-born, he's a Brit. Uh, neuroscience at Nottingham University, PhD at Newcastle, then he went to Harvard, uh, Medical School, and he's been at, uh, UC Berkeley since two thousand and seven. And in twenty seventeen, as I say, he published, uh, this book, which was four years in the writing. He also has, uh, a consulting relationship with Google through our sister company, Verily. So please welcome Matt Walker. [cheering] [applauding]

    2. MW

      Thank you, Matt.

    3. MB

      Matt, welcome.

    4. MW

      Thank you.

    5. MB

      I should say welcome back to Google 'cause you've, you've been, uh, you've done a t- a talk at Google before, so we're delighted to have you back.

    6. MW

      I have, yeah, so it's a delight to be back and fascinating to see the hands that are sort of going up. For those of you who answered that you were getting seven hours or less, um, I'll just start with a quick fact. The number of people who can survive on seven hours of sleep without showing any impairment, rounded to a whole number and expressed as a percent of the population, is zero.

    7. MB

      [laughing]

    8. MW

      Good luck. [laughing]

    9. MB

      Okay, so hopefully you'll give some guidance and some case to change to all of us.

    10. MW

      I will do.

    11. MB

      [laughing] Don't despair.

    12. MW

      [laughing] There's hope on the way, trust me.

  3. 3:10 – 4:58

    How much sleep is enough—and a simple self-test with your alarm

    1. MB

      Yeah. W- w- well, I think what I'd like to do is, is start with just the basic, uh, question, like what is enough sleep, and what goes wrong when we don't have enough sleep?

    2. MW

      So right now we recommend somewhere between seven to nine hours of sleep. Um, the sweet spot is probably about eight for most, uh, human adults. Uh, how do you know if you're not getting enough sleep is sort of one of those questions. Several things. Firstly, if you were setting an alarm-- By the way, I'm going to probably just look at you, Matt, 'cause I know there's this strange thing that happens with an audience where you sort of-- I'm not t- to you t-

    3. MB

      You can try, but you may want to divert, you may want to divert your eyes

    4. MW

      I will, I will just speak to you. But one of the things is if you set an alarm and the alarm didn't go off, would you sleep past your alarm? And if the answer is yes, then you're not done with sleep yet.

    5. MB

      Right.

    6. MW

      And in fact, when we've studied sort of hunter-gatherer tribes whose way of life hasn't changed in thousands of years, and you speak about this sort of artificial termination of sleep, they're utterly puzzled. You know-

    7. MB

      Wow

    8. MW

      ... why would you stop something that hasn't yet completed?

    9. MB

      Mm.

    10. MW

      Um, what's also fascinating, by the way, is that if you ask them about sleep difficulties, here in most developed nations, the insomnia rate is about ten to fifteen percent. There, based on our estimates, it's about one to two percent. They just don't understand the concept of not being able to sleep. So there's something about modernity that's desperately dislocated-

    11. MB

      Right

    12. MW

      ... us from this thing called a good night of sleep.

    13. MB

      Right. And so, and le- let's just talk for a minute. So a lot of what you cover in the book and you've covered in your research is, is the health issues that arise from lack of sleep. So just, just tell us, let's start with the worst, right? So w- w- what-

    14. MW

      Yeah

    15. MB

      ... what happens to you? Cognitively, fitness-wise, illness-wise, attractiveness-wise. What are the things that happen? [laughing]

  4. 4:58 – 8:39

    Sleep loss shows up fast: appearance, learning, and emotional control

    1. MW

      Let me start with attractiveness.

    2. MB

      Yeah.

    3. MW

      So we've all heard of this thing called beauty sleep. You know-

    4. MB

      Mm

    5. MW

      ... sort of this, um, old tale that you would get. Well, it's actually true, and there was a wonderful study done in Sweden, and they took a group of healthy young individuals, and they gave them a full night of sleep, and then they deprived them a night of sleep. So they went through the experiment twice, and at the end of each one of those, after a good night of sleep or being sleep-deprived, they took a portrait shot. And then came the second part of the experiment, which was essentially a beauty contest, where they took independent judges who knew nothing about the two experimental conditions, and they just said, "Rate these pictures on the basis of how attractive, how healthy people look, how sickly they look, how tired or sleepy they look."

    6. MB

      Right.

    7. MW

      And cons- even though these judges knew nothing about the experimental conditions, they routinely rated you when you were shot under conditions of being sleep-deprived as being less attractive, looking more sickly, and looking a lot more tired. So-

    8. MB

      That's after one night

    9. MW

      ... after one night. So there is objectively a thing called beauty sleep-

    10. MB

      Wow

    11. MW

      ... and people independently can, can see it. Now, which is no surprise-

    12. MB

      Yeah

    13. MW

      ... you know, 'cause people will come in all of the time, and they'll sometimes say to you, if they're honest, they'll say, "Wow, you know, you look tired."

    14. MB

      Yep.

    15. MW

      How, how do you know that? Because it turns out that there are-

    16. MB

      Can read people really well

    17. MW

      ... clear facial cues and-

    18. MB

      Right

    19. MW

      ... bodily cues that express this thing called insufficient sleep, and other human beings can pick up on it.

    20. MB

      Right, so thing one, you get less attractive.

    21. MW

      Yeah.

    22. MB

      Uh, there are other things, though, too. What happens to you cognitively? What happens to your capability to make decisions, to learn, to do all the stuff we have to do in a working environment?

    23. MW

      So if you're not sleeping, the, one of the first things that you become deficient in is your capacity to learn. So we've done studies where we will, again, deprive people of sleep or give them a full night, and then we'll try and have them learn a whole list of new facts. So essentially, is pulling the all-nighter a good idea? And the answer seems to be no, because the brain is about 40% deficient in-

    24. MB

      Yeah

    25. MW

      ... its ability to lay down new memory traces when it is underslept. And 40% is non-trivial. I mean, that's-

    26. MB

      Yeah, it's huge

    27. MW

      ... the difference between acing an exam and failing it miserably. Um, and I think that's particularly concerning for sleep in our education populations-

    28. MB

      Yeah

    29. MW

      ... right now. We also know that you need sleep after learning, however, not just before learning, to essentially hit the save button on those new memories so that you don't forget. Um, one of the other things that starts to go awry is your emotional stability. What we found is that there's a deep structure in the brain called the amygdala, and it's the centerpiece region for the sort of generation of strong emotional reactions, impulsive reactions. The reason that you typically are not impulsive and you're emotionally rational is because another part of your brain called the prefrontal cortex, which sits above your eyes, that's like the CEO of the brain. It's very good at making high-level, top-down kind of controlling decisions.

    30. MB

      Mm-hmm.

  5. 8:39 – 11:37

    Chronic sleep loss and Alzheimer’s: the brain’s nighttime cleaning system

    1. MW

      more emotionally irrational as well upstairs in the brain. Um, the other thing I would note, by the way, that's increasingly now interesting within the brain is not an acute effect but a chronic, chronic effect. That chronic effect concerns Alzheimer's disease, and we now know that insufficient sleep is probably one of the most significant lifestyle factors determining whether you will develop Alzheimer's. Why is that? The reason is because at night, there is a cleansing system that kicks into high gear within your brain.

    2. MB

      Mm-hmm.

    3. MW

      So in your body, you have a cleaning system called the lymphatic system. Well, in your brain, we recently discovered that you have something called the glymphatic system, 'cause it's made out of these cells called glial cells.

    4. MB

      Right.

    5. MW

      And at night, it's during deep sleep when that cleansing system kicks into high gear, and it washes away all of the toxic metabolic byproducts that build up during the day.

    6. MB

      Mm-hmm.

    7. MW

      Because wakefulness is low-level brain damage.

    8. MB

      Right.

    9. MW

      One of the sticky toxic proteins that it washes away at night is a protein called beta amyloid.

    10. MB

      Mm-hmm.

    11. MW

      And if you deprive rats of sleep, they immediately start to escalate the amount of this Alzheimer's protein in their brain after just one night. We've now done the same experiments in humans, and you can see that causal trigger after just one night.

    12. MB

      And this is like taking the plaque out of the brain, effectively.

    13. MW

      Exactly, so it's essentially good night sleep clean in that sort of sense.

    14. MB

      And I, I, I read, so I was gonna ask you about this. I read that, um, you sort of got into this whole area way back when you were actually looking at Alzheimer's and trying to understand sort of why Alzheimer's seemed to lead people to sleep less, but actually realized that it was the other way around, that it was sleeping less that was contributing to the Alzheimer's. Is that, is that how it worked out?

    15. MW

      Yeah, so I think we're all accidental sleep researchers in the field.

    16. MB

      Right. [laughs]

    17. MW

      You know, no one, sort of when they're a child and they go around the classroom and they say, "What would you like to be when you grow up?" No one says, "I'd love to be a sleep researcher." [laughs]

    18. MB

      [laughs]

    19. MW

      Um, and I fell into it by accident. You know, during my PhD, I was trying to use brainwave patterns to diagnose people with different types of dementia very early on.

    20. MB

      Mm-hmm.

    21. MW

      And I was failing miserably for the-

    22. MB

      Mm

    23. MW

      ... first couple of years. And then I used to go home, and I had this sort of little igloo of journals in my room, and I'd read them at the weekend. And then one weekend, I realized, uh, reading an article, that in some dementias, like Alzheimer's, the centers that generate sleep-

    24. MB

      Yeah

    25. MW

      ... are those that are attacked by the disease, whereas in other types of dementia, like vascular dementia, you typically don't have that. So I thought, "Well-

    26. MB

      Right

    27. MW

      ... maybe I'm measuring my patients at the wrong point in time when they're awake. I should be measuring them whilst they're asleep."

    28. MB

      Right.

    29. MW

      Started measuring their sleep, got some great results, and at that point I then said, "If sleep is so disrupted in these Alzheimer's patients, is it not just simply a symptom of the disease? Could it actually be a causal trigger of the disorder?"

    30. MB

      Right.

  6. 11:37 – 13:00

    Aging, deep sleep decline, and why older adults still need the same sleep

    1. MW

      Yeah, so we do a huge amount of work, um, with aging and Alzheimer's disease. We know that, you know, a, a psychological signature of aging is that our memory gets worse, but a physiological signature of aging is that our sleep gets worse.

    2. MB

      Right.

    3. MW

      And only recently, we published evidence that those two things are not simply co-occurring, they are significantly interrelated. And what's exciting, or, you know, that may sound very depressing that it's in the mail, it's coming at you, it's-

    4. MB

      Mm-hmm

    5. MW

      ... it's non-negotiable, but- Unlike many of the other factors that are associated with brain aging, for example, changes in the physical structure of the brain, um, or even the vasculature of the brain, those are fiendishly difficult to treat.

    6. MB

      Mm-hmm.

    7. MW

      But that sleep is a missing piece in the explanatory puzzle of aging and Alzheimer's is exciting because we may be able to do something about it.

    8. MB

      Right. 'Cause it does, it does get harder... Am I right in saying it gets harder to sleep as you get older?

    9. MW

      Yeah.

    10. MB

      What changes exactly?

    11. MW

      So one of, one of the myths is that older adults need less sleep.

    12. MB

      Right.

    13. MW

      And that's nonsense. Older adults need just as much sleep as they did when they were in their 40s or their 50s. The difference is that their brain cannot generate the sleep that it still necessarily needs. The reason is because parts of the brain that deteriorate most quickly and early during the course of aging are unfortunately the same centers that generate our deep sleep.

  7. 13:00 – 15:50

    Sleep and the body: reproductive health and cardiovascular risk

    1. MB

      Right. Okay. Wow. Um, so you've, you've covered a, a lot there, but you haven't covered, like, the role of sleep in road deaths. You touched on education, but tell us a bit more about some of the downsides that you're increasingly clear on in terms of sleep-deprived populations.

    2. MW

      Yeah, so in terms of, we've sort of spoken a little bit about the brain. I, um-

    3. MB

      Mm

    4. MW

      ... let me speak a little bit about the body. I think the best place to start there is testicles. Um- [laughs]

    5. MB

      [laughs]

    6. SP

      [laughs]

    7. MW

      'Cause why wouldn't you?

    8. MB

      So I would say, yeah. Why not?

    9. MW

      [laughs] Uh, so we, what we know is that men who sleep five hours a night have significantly smaller testicles than those who sleep seven hours or more. Um, in addition, men who-

    10. MB

      Is that, i- that's relevant because?

    11. SP

      [laughs]

    12. MW

      Well, [clears throat]

    13. SP

      [laughs]

    14. MW

      Struggling to come up with an answer to that one, but, um-

    15. MB

      Is, is it to do with fertility or?

    16. MW

      Well, it- what's also interesting is that if you look at the sex hormones-

    17. MB

      Yeah

    18. MW

      ... men who are sleeping four to five hours a night will have a level of testosterone which is that of someone 10 years their senior.

    19. MB

      Wow.

    20. MW

      So a lack of sleep will age a man by a decade in terms of that critical aspect of wellness. We see equivalent impairments in female reproductive health caused by a lack of sleep.

    21. MB

      Okay.

    22. MW

      So if you end up having a couple that's trying to, you know, start a family-

    23. MB

      Yeah

    24. MW

      ... and they're both underslept, it's actually much more difficult-

    25. MB

      Yeah

    26. MW

      ... to try and, you know, develop a genetic legacy in that regard.

    27. MB

      Wow, okay. So, so in terms of sleep effect on the body, reproductive health-

    28. MW

      Reproductive health is the first one.

    29. MB

      Right.

    30. MW

      I think the next one I would speak about is sleep and cardiovascular disease. The links there between a lack of sleep and, you know, heart attack and stroke-

  8. 15:50 – 17:28

    Why drowsy driving can be deadlier than drunk driving: microsleeps

    1. MB

      And, and I, I know you, you talk about, um, the, the time of day that education starts, and you also talk about road accidents in the context of sleep, two, two really big social issues. So, so road accidents, you, you, you're claiming here, um, that sleep's a bigger killer than alcohol or drugs in, in road deaths. So te- tell us why that is.

    2. MW

      So when you are underslept, you, if you're cr- if you're severely sleep-deprived, you can typically fall asleep at the wheel.

    3. MB

      Mm.

    4. MW

      But that's usually not what happens. Most people are chronically underslept.

    5. MB

      Right.

    6. MW

      They're trying to survive on six hours of sleep or less or... Um, and what you typically then have are what are called microsleeps-

    7. MB

      Right

    8. MW

      ... where your eyelid will just partially close and the brain essentially just goes to sleep for a second or two.

    9. MB

      Right.

    10. MW

      Now, if you're traveling at, you know, 70 miles an hour on a motorway and you have one of these microsleeps for two seconds, at a moderate drift angle, you're in the next lane-

    11. MB

      Mm

    12. MW

      ... which means that you could be on, you know, incoming traffic. That's the first issue. The second reason that, um, drowsy driving is usually much more fatal in terms of its damaging, in terms of car crashes, is the following. When you're drunk or you're high, you typically react too late.

    13. MB

      Right. So reactions are slowed down-

    14. MW

      Slowed down

    15. MB

      ... but you're reacting.

    16. MW

      But you're reacting.

    17. MB

      Right.

    18. MW

      When you are sleep-deprived, you don't react at all-

    19. MB

      Right

    20. MW

      ... because you have a microsleep.

    21. MB

      Right.

    22. MW

      So at that point, there is a two-ton missile traveling at 70 miles an hour on the motorway, and no one is in charge. That's why sleep-related accidents are usually much more deathly than drowsy dri- than, sorry, drink driving or drugs.

  9. 17:28 – 21:02

    Teen sleep biology and early school start times—and sleep’s image problem

    1. MB

      Some amazing insight. And, and then on education, as a father of teenagers, I know this, um, the hour at which we start the school day and how that changes, particularly as somebody's growing up from sort of childhood through teens, you know, our sleep needs seem to change in that period as well. Tell us a little bit about that and, and the impact that you've sort of identified there.

    2. MW

      I think this is a real problem that we've consistently started to roll back education times. It's, it's better here in the United Kingdom than it is in the United States, but I know that there was a push recently, uh, in the government level to try and delay school start times until 10 o'clock in the morning.

    3. MB

      Mm.

    4. MW

      That's the bare minimum for a teenage brain. The reason is because as we go through adolescence, our biological preference for going to bed and waking up changes-

    5. MB

      Mm

    6. MW

      ... that we've moved forward in time. We want to go to bed later, and we want to wake up later.

    7. MB

      Why, why would that be? Do you know why that is?

    8. MW

      So we know the biology, and we know why it's happening from a sort of a mechanistic standpoint from- At evolutionary standpoint, that's an interesting question. I think one of the things that I posit in the book-

    9. MB

      Mm

    10. MW

      ... is that that's the moment in time when you need to cut the cord from parental influence. You need to kind of flee the nest, and you need to start testing the waters out by yourself in your own social community as you become a young adult.

    11. MB

      Mm.

    12. MW

      What better way to do that than actually now going to bed later than your parents, but yet your cohort, your sort of brethren of that age, are also staying up later-

    13. MB

      Right

    14. MW

      ... and then you wake up later. So it may be a time when you can actually start to develop yourself as an adult independent of parental influence [drowned by speaker]

    15. MB

      So my teenagers aren't lazy, they're just natural.

    16. SP

      [laughs]

    17. MW

      They're, they're just doing simply what their biology does.

    18. MB

      Right.

    19. MW

      And that's one of the problems, is that we have- sleep has a terrible image problem in society.

    20. MB

      Mm.

    21. MW

      That we label people who get sufficient sleep as, you know, slothful or even lazy.

    22. MB

      Right.

    23. MW

      You know, and I noticed that when you said, you know, what about the people who get, uh, nine hours of sleep or more, and I see this all the time, these sort of hands-

    24. MB

      [laughs]

    25. MW

      ... these shamed hands sort of go up, um, you know, sort of

    26. MB

      [laughs]

    27. MW

      You know. And I have this at talks where there will be people who wait all the way to the end, and they don't want to come to the mic and ask the question.

    28. MB

      Yeah.

    29. MW

      And they'll sidle up to me and they'll say, "Look, I'm, I'm one of those people who probably needs about eight or nine hours of sleep a night," as if it's this horrific thing to admit.

    30. MB

      We should be, we should be cheering them on.

  10. 21:02 – 24:49

    Why modern life erodes sleep: time pressure, screens, and anticipatory anxiety

    1. MB

      That's amazing. So, um, we could spend a long time talking about bad effects of not enough sleep, but let- let's talk a little bit about the causes, and then what you can do to improve if we can. So, um, you alluded to it there, like, one of the causes is obviously light, natural light, or, sorry, artificial light allowing us to extend the waking hours. But what, what causes bad sleep? What are the kinds of things that, that make us sleep badly today?

    2. MW

      So I think it's important to separate out two things. One is having problems with sleeping-

    3. MB

      Right

    4. MW

      ... the other is having the opportunity to sleep.

    5. MB

      Yeah.

    6. MW

      So, and both of those things will constrain your sleep. One of the problems with opportunity, the reason that most people don't get the chance to sleep even if they could sleep that amount, um, are, there are a number of reasons. Firstly, we are typically working longer hours and we're commuting for longer periods of time, which means that most people are leaving the house earlier and coming home later.

    7. MB

      Right.

    8. MW

      Nobody wants to sho- sort of shortchange their TV time or their family time, so the one thing that gets squeezed like vice grips in the middle of the night is this thing called a normal eight-hour sleep period. Um, then we've also spoken about the stigma-

    9. MB

      Yeah

    10. MW

      ... that, the, the shame of getting sufficient sleep. Then you can start to come into the home and ask what else is compromising your sleep. We certainly know that blue light emitted from devices can compromise your sleep. There's a fascinating study where they had people reading on an iPad for one hour before bed versus just reading a normal book-

    11. MB

      Yeah

    12. MW

      ... in dim light. And what they found was that the iPad reading, firstly, it delayed the release of a hormone called melatonin, and that hormone needs to be, um, in high amounts to time the healthy onset of your sleep. But the iPad reading before bed decreased the amount of melatonin that was released by 50%, so it slashed it in half, and furthermore, it delayed the onset of that melatonin by about three hours. So, you know, you're much closer to Russian time than you are UK time if you're reading an iPad for one hour before bed.

    13. MB

      Wow.

    14. MW

      The third thing is that it disrupted their REM sleep. They had actually a reduction in their dream sleep, which is critical for things like mental health. So the invasion of, I think, technology into our environment-

    15. MB

      Mm

    16. MW

      ... particularly blue light, is a harm. But that's not the only issue. Um, I think technology is, and I'm mindful of course of where I'm speaking, but-

    17. SP

      [laughs]

    18. MW

      You know, one of the things that technology can cause is just anxiety-

    19. MB

      Mm

    20. MW

      ... and stress, and a lot of people keep their phones in their rooms, and the first thing that they do when they wake up in the morning is, you know, hit your PIN code and-

    21. MB

      Yeah

    22. MW

      ... this tsunami of the world just invades you, and you train your brain to expect that every morning. It's called anticipatory anxiety.

    23. MB

      Right.

    24. MW

      And it lightens your sleep, it prevents you from going into the deeper sleep. So the advice there would be, you know, try to see if you can abstain from opening your phone until after you've brushed your teeth.

    25. MB

      Yes. There's a great advice-

    26. MW

      It's just the first-

    27. MB

      ... which is, um, if the first thing you touch in the morning is your phone and not your partner, you're in trouble.

    28. MW

      That's right. Yeah. And w- that is not going to be a, a partnership that will last for too long. Um, so-

    29. MB

      Pay attention, folks

    30. MW

      ... um, but and then just scale it back, say, you know, could I do it until, you know, not look at my phone until I've had breakfast?

  11. 24:49 – 28:44

    Darkness, dim lights, stress, caffeine, and alcohol: common sleep disruptors

    1. MB

      Right

    2. MW

      ... to things that are preventing your sleep. So we are a dark-deprived society. We need that darkness at night.

    3. MB

      Mm-hmm

    4. MW

      So trying to stay away from screens in the last hour before bed.

    5. MB

      Yeah.

    6. MW

      Also dimming down the lights in your home.

    7. MB

      Mm-hmm.

    8. MW

      Sort of drop the lights by 50%.

    9. MB

      Yeah.

    10. MW

      You'll be surprised at how soporific that actually is. Um, I think one of the other aspects above and beyond stress, which is a key thing, uh, triggering insomnia, is alcohol and caffeine use.

    11. MB

      Yeah.

    12. MW

      So, um, this usually makes me deeply un- unpopular, [laughs] uh, when I describe... I'm, I'm generally unpopular, but this makes me even more unpopular.

    13. SP

      [laughs]

    14. MW

      Um, firstly, caffeine.

    15. MB

      Yeah.

    16. MW

      Caffeine, everyone knows, keeps you awake. It's an alerting substance. It's the only psychoactive drug that we readily give to our children with- without too much concern. But caffeine also is misunderstood in terms of its duration of action. So caffeine has a half-life of about six hours and a quarter life of 12 hours. What that means is that if you have a cup of coffee at noon, half of, uh, that caffeine is gone by, you know-

    17. MB

      6 PM

    18. MW

      ... 6 PM.

    19. MB

      Yeah.

    20. MW

      But it means that there's still a quarter of that caffeine swilling around in your brain at midnight.

    21. MB

      That's amazing.

    22. MW

      So in other words, if you were to take a cup of coffee at noon, it's the equivalent of getting into bed at midnight and before you turn the light out, you swig a quarter of a cup of coffee and you hope for a good night of sleep, and it's probably not going to happen.

    23. MB

      So what's the latest I can have my coffee?

    24. SP

      [laughs]

    25. MW

      I would scale back 14 hours before bed.

    26. MB

      Wow.

    27. SP

      [laughs]

    28. MW

      And then [laughs] ... Really [laughs]

    29. MB

      Can I have a lot of coffee early?

    30. MW

      So you can drink, you can strategically drink caffeine to help-

  12. 28:44 – 33:45

    How sleep is structured: non-REM stages, deep sleep restoration, and REM dreaming

    1. MB

      So I wanna come to questions, uh, from all of you in a, in a couple of moments if I may. But, but before we do that, let's just sort of talk a little bit more. You, you alluded to there sort of why we sleep, which is the whole title of your book, and, um, you know, the huge benefits to our health and wellbeing from sleeping well. Um, but, but what actually happens during sleep? Um, what is the process? You mentioned REM sleep, dreaming. Just tell us a little bit about what's going on and why it's so important. What have you discovered?

    2. MW

      So let me tell you a little bit about how sleep works and then, um, what it does. Um, we all have two basic types of sleep. One is called non-rapid eye movement sleep, or non-REM sleep for short. The other is rapid eye movement sleep. And non-REM sleep is further subdivided into four separate stages, um, unimaginatively called stages one through four-

    3. MB

      Right

    4. MW

      ... uh, increasing in the depth of sleep. So stages three and four of non-REM are the deep stages of dreamless sleep.

    5. MB

      Dreamless. Um, and-

    6. MW

      Dreamless

    7. MB

      ... that's the, when the body's mending itself? What's happening in those stages?

    8. MW

      Um, it is one of the times, one of the stages where the body goes through a remarkable restoration. We see sort of protein synthesis. We see rebuilding of cells. Um, deep sleep is probably one of the very best blood pressure medications that you could ever wish for. It's during deep sleep that we get cardiac deceleration. Your heart rate plummets. Your blood pressure drops. It's essentially a reset for your cardiovascular system. It's also during deep sleep, but also REM sleep, when you restock the armory of your immune system.

    9. MB

      Mm-hmm.

    10. MW

      And that's why when you start to sleep less, you're far more vulnerable to infection. In fact, if you're sleeping five hours a night, you're four times, 400% more likely to catch a cold than if you're sleeping eight hours or more.

    11. MB

      Wow.

    12. MW

      Another demonstration of this is if you get a flu shot, um, and, you know, we'll sort of be, uh, you know, four months away from, from that time period, but you're not getting enough sleep, if you've only been sleeping, let's say, five or six hours in the week before you get your f- your flu shot, you only produce half of the normal antibody response, rendering that flu shot largely useless because your immune system is so impoverished that it can't respond to the antigen.

    13. MB

      These are massive numbers you're quoting here in terms of the impact of these things. Huge.

    14. MW

      Yeah, and, you know, why, why is that? Why- Why can I quote such large numbers? You know, is it just sort of a lot of hand-waving and, and plucking of the, the cherries in terms of the data? And the answer is no, and the reason is this: human beings are the only species that deliberately deprive themselves of sleep for no apparent reason. And the reason I make that point is Mother Nature has therefore never had to face the challenge of sleep deprivation throughout the course of evolution, so she's never had to come up with safety nets-

    15. MB

      Right

    16. MW

      ... to risk mitigate this when it happens. Now, there is precedent in biology for that. You know, why can't we, for example, bank sleep-

    17. MB

      Yeah

    18. MW

      ... and then use it when we're going to be sleep-deprived? That would be lovely. And there is a method like this in biology. It's called the fat cell. Because there were times during our evolutionary past when we faced a feast, and then we had famine. So Mother Nature, facing that challenge, created this thing called the adipose cell, the fat cell, so you could store caloric credit and then spend it when you had a debt, when you had a famine. Where is the fat cell for sleep?

    19. MB

      Oh, you should invent that.

    20. MW

      I would love to. I would make so much money out of it. But the, the reason it doesn't exist is because we've never had that challenge.

    21. MB

      Right.

    22. MW

      Humans are the only species that do that.

    23. MB

      That's amazing. So you, you were talking then about NREMs, uh, non-REM sleep, and they're going deeper and deeper.

    24. MW

      Yeah, so those two types of sleep will play out in a battle for brain domination throughout the night, and you'll start to gradually, as you fall asleep, go into the light stages of non-REM, then down into the deep stages of non-REM, and then after about 60 or 70 minutes, you'll start to rise back up and you'll have a short REM sleep period. And then you go back down again, down into non-REM, up into REM.

    25. MB

      Um, right, and so the REM sleep you haven't touched on, so tell us a bit about that. That's when we're dreaming and moving.

    26. MW

      That's ... Yeah, and in fact, when you look at the brainwave activity in dreaming, it's indistinguishable from that when we're awake. In fact, some parts of your brain are up to 30% more active when you're in REM sleep than when you're awake.

    27. MB

      So you ... Some parts of your brain are, are more awake than when you're awake?

    28. MW

      That's right.

    29. MB

      That's in-

    30. MW

      They're more active when you're in REM sleep than when you're awake. Other parts of the brain, however, switch off.

  13. 33:45 – 35:03

    Sleep as a biomarker: REM behavior disorder, disease forecasting, and prevention vs treatment

    1. MW

      It's a, it's a 90-minute cycle.

    2. MB

      How old do you have to be for that?

    3. MW

      Uh, it usually starts in people in their 50s.

    4. MB

      Oh, dear. Okay.

    5. SP

      [laughs]

    6. MW

      And, and one of the, the, the difficult things is that if you have REM sleep behavioral disorder, it markedly increases your risk probability of Parkinson's disease, we've been finding. So there are things in your sleep that can foretell, that can forecast-

    7. MB

      Mm

    8. MW

      ... your disease risk-

    9. MB

      Mm

    10. MW

      ... 10 or 20 years ahead of time, and this is a lot of work that we're doing right now at the sleep center. How can we use sleep as a new biomarker that is predicting your disease risk decades ahead of time? And the reason that that's important is because right now in health care, we actually don't have a model of health care. We have a model of sick care, which is that we are principally interested in treatment.

    11. MB

      Mm.

    12. MW

      What we need to have is a model of truly health care.

    13. MB

      Yeah.

    14. MW

      If you do that, it's a model of-

    15. MB

      It'll be health care

    16. MW

      ... prevention-

    17. MB

      Yeah

    18. MW

      ... not a model of treatment.

    19. MB

      Right.

    20. MW

      And if you can find things that are sort of f- foretelling your disease risk way ahead of time, you give yourself the opportunity window to do something about it.

    21. MB

      To fix that.

    22. MW

      And sleep seems to carry within it, nested in its static of electrical brainwaves at night, it seems to have lots of these health biomarkers that are disease-risk-

    23. MB

      Mm

    24. MW

      ... uh, protective or predictive.

  14. 35:03 – 37:35

    What dreams may be doing: replay, memory saving, and creative association

    1. MB

      Now, when I was reading about REM sleep in your book, you, you mentioned not just the fact that some parts of our brain are more active, but also that we're replaying the day's memories at 20x normal speed. And there's a sort of theory that we're kind of defragmenting and sort of filing in that sleep, but what really is going on in REM sleep?

    2. MW

      So in the studies with rats, what they've done is they've had them run around a maze, and they've got electrodes in the brain, and you can pick up this kind of electrical signature of learning as it's running around the maze. And let's say that you just make each one of those brain cells have a tone to it, and so the rat is running around the maze and you just hear this sort of brain cell firing as it's coding the maze, and it sort of goes ba ba ba bum, ba ba ba bum, ba ba ba bum. And then what was fascinating in those studies is that they then let the rats sleep, and what you heard was this replay, ba ba ba bum, ba ba ba bum, but it wasn't at that speed. It was 20x, so it was like ru ru ru ru ru.

    3. MB

      So it literally is happening. That's incredible.

    4. MW

      And so what we see is that the brain is actually essentially replaying those memories almost as though what it's doing firstly is scoring the memory trace or etching the memory trace more powerfully into the brain so that when you wake up the next day, you can better remember the things that you learned before, and we know that sleep is-

    5. MB

      Mm

    6. MW

      ... wonderful for doing that. That actually happens during deep non-rapid eye movement sleep. What happens during REM sleep is something more interesting. There the brain almost becomes chaotic and random, and what we think is happening during REM sleep is that during deep sleep you take the information you've learned and you save it. You hold onto it. Then it's during REM sleep that we say, based on the information that we've learnt today, how does it interrelate with everything that we've previously learned? How do we figure out which connections we should build and which we should let go of? And it seems as though dream sleep is a form of informational alchemy that you start- it's almost like memory pinball. You start bouncing it around the attic of all of your memories and saying, "Should this be a connection? Should this be a connection?"

    7. MB

      Wow.

    8. MW

      But REM sleep is almost like a Google search gone wrong, that it's during REM sleep that you input your search term, and it immediately takes you to page 20-

    9. MB

      Right

    10. MW

      ... which is about some bizarre thing. And you think, "Hang on a second. Is there a really?" And but there is a strange-

    11. MB

      There's some sort of-

    12. MW

      ... tangential link. It's during dream sleep that we test out the most bizarre, strange, associative connections, and that's the reason that you wake up the next morning often having divine solutions to-

    13. MB

      Right

    14. MW

      ... previously impenetrable problems. That's what dream sleep seems to be about as well.

  15. 37:35 – 56:40

    Audience Q&A: jet lag, ‘first-night effect,’ parenting sleep loss, tracking, naps, and best practices

    1. MB

      Oh, that's incredible to, to sort of understand just the beginnings o- of, of that and how it works. And so, um, I'd like to invite people to come to the mic. We have our first questioner here. Do you wanna speak up and find out about sleep?

    2. SP

      I, uh, just a quick question if it's working.

    3. MB

      Yep.

    4. SP

      Yes. Um, do you have any tips on dealing with jet lag? So anything we can do to improve?

    5. MW

      So our bodies were never designed to be fast-forwarded through time with this thing called the jet engine. [laughs]

    6. SP

      [laughs]

    7. MW

      And it causes a biological lag, a mismatch between your internal clock and the place that you arrive, and that's what we call jet lag. There are some treatments, quote, unquote, but there is no cure. Um, the treatments are probably the following. The first is most people sleep at the wrong time on the flight. So let's say I'm traveling from San Francisco back to London. The first thing you need to do as soon as you get on the plane is change all clocks to the new time zone, so you're now immediately reminded what you're working with in terms of a time structure. The second, if I'm- most people on that flight over from San Francisco are probably going to be sleeping in the, the second half of the flight. Now, I will touch down at around about 11 o'clock in the morning. That means that most people are sleeping on London time from about, you know, 7 o'clock in the morning through until 11 o'clock in the morning. Why is that a problem? The longer that you're awake throughout the day, the more sleepiness that you build up in the brain. It's a chemical called adenosine. The sleepier that you are, the more likely you are to fall asleep and stay asleep. But o- one of the problems is that if you sleep too late on the flight, essentially it's like waking up at 11 o'clock in the morning, and then when it comes to go to bed at the normal time in London, you're not going to be tired because you were sleeping until 11. So sleep in the first half of the flight, then brute force yourself awake, stay awake, and then stay awake for the entirety of that following day. Don't be tempted to nap because if you nap, again, you release some of that sleepiness. It's almost like a pressure valve on a cooker, and it will make it that much harder to fall asleep that following evening. That first night, if you nail that first night with a good night of sleep, it's a great way to reset your biological clock. Once you're in the new time zone, two more recommendations. The first is, in the morning, go out and get daylight, at least 20 to 30 minutes outdoors. When you do that in the morning, even if it's sunny, don't wear sunglasses. I know it's cool, but you need to get that light into the brain. The other one is eat at the regular times when everyone else is eating, not when you're hungry because food, we've discovered, is just as powerful a resetting trigger on your internal clock as light is.

    8. SP

      Oh.

    9. MW

      And then if you want to, you can strategically use melatonin. It's not available over here, but it's available in other countries.

    10. SP

      [laughs]

    11. MW

      Usually take that, uh, about an hour before bed. Most people dose too much. They usually do 5 to 10 milligrams. It should really be .5 to 3 milligrams. Just be mindful, however, that if you get it in America, it's not regulated by the government. One study found that if you looked at 20 brands based on what it said on the label, what was actually in those pills were either 80% less than what it said on the label up to 160% more than what it said on the label. So it's a bit of a Wild West. You've got to be careful. But those would be the tips for jet lag.

    12. SP

      Thank you.

    13. MB

      It's a minefield. Great tips. And actually, one other thing while you're on the subject of travel, 'cause quite a few of us do, is, um, sleeping somewhere unfamiliar also has-

    14. MW

      Mm

    15. MB

      ... an impact on your sleep. Just tell us a little bit about that 'cause it's also useful for, for this group.

    16. MW

      It is. So you will sleep, um, almost with one half of your brain differently than the other when you travel. So there are some species like dolphins, for example, who can sleep entirely with one half of their brain. Otters do this. Most aquatic mammals have what we call unihemispheric sleep, which is that one half of their brain is awake, the other half is asleep, and when that half has had its fill, it switches over. Now, it would- wouldn't it be lovely if we could do that? [laughs] You could sort of keep working, and one half of your brain is sleeping, and then it switches over. Um, but humans, actually we didn't think they could do that, but they have a, a sort of a diet version of that, a lite, L-I-T-E version of that. Whenever you sleep in an unfamiliar location, what we found is that one half of the brain does not sleep as deeply as the other half of the brain, almost as though it's sort of trying to keep watch and maintain some degree of vigilance.

    17. MB

      Right.

    18. MW

      And that's probably the reason why a lot of people will say, you know, that first night in the hotel-

    19. MB

      Never feels-

    20. MW

      ... I typically-

    21. MB

      Yeah

    22. MW

      ... you know, never feels good. I never quite sleep when... Or this phrase, you know, "I can't wait to get back to my own bed."

    23. MB

      Yes.

    24. MW

      You know, it's, in some ways, it's familiarity. In other ways, it's the depth of your sleep as well.

    25. MB

      Really fascinating. Next question.

    26. SP

      Uh, hi, Matthew.

    27. MW

      Hi.

    28. SP

      Um, my name is Alice. I have a 10-month-old boy and a four-year-old boy. I don't get a lot of sleep. You're scaring the life out of me right now. Um, [laughs]

    29. MW

      Well, it's actually the lack of sleep that's taking the life out of you right now, but let's-

    30. SP

      [laughs]

Episode duration: 56:55

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