[MUSIC PLAYING] MATT BRITTIN: Hello, everybody. AUDIENCE: Good morning. MATT BRITTIN: Happy Monday. [CHEERS AND BOOS] Yeah, mm, kind of. Have you ever read a book
and been on a mission to get other people to read that
book, like "The Great Gatsby," or what books were you on a
mission to get people to read? AUDIENCE: This one. MATT BRITTIN: This one? Yeah, this one. AUDIENCE: No, seriously. MATT BRITTIN: Seriously. Me, too, actually. So a few years ago, I read
some research about sleep. And 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 on
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 it's author,
our legendary guest speaker and sleep diplomat,
Matt Walker, I just want to 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. OK. So how many people got between
five and six hours' sleep last night? Oh, that's about
20 people or so. What about six to
seven hours' sleep? Oh, about a third of
the people, maybe. Seven to eight? Eight to nine? [LAUGHTER] Anybody got more than
nine hours' sleep? Yes! Congratulations. Anybody have young children? You probably need to leave
the room at this point. OK. Time to get on 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
100 research studies. He's Liverpool-born. He's a Brit. Neuroscience at Nottingham
University, PhD at Newcastle. Then he went to
Harvard Medical School, and he's been at UC
Berkeley since 2007. And in 2017, as I say, he
published this book, which was four years in the writing. He also has a consulting
relationship with Google through our sister
company, Verily. So please welcome Matt Walker! [CHEERS AND APPLAUSE] MATTHEW WALKER: Thank you, Matt. MATT BRITTIN: Matt, welcome. MATTHEW WALKER: Thank you. MATT BRITTIN: I should say
welcome back to Google. Because you've done a
talk at Google before, so we're delighted
to have you back. MATTHEW WALKER: Yeah. So it's a delight to be back. And fascinating to see the
hands that are going up. For those of you who
answered that you were getting seven
hours or less, 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. [LAUGHTER] Good luck. MATT BRITTIN: OK. So hopefully, you'll give
some guidance and some case to change to all of us. MATTHEW WALKER: I will do. MATT BRITTIN: Don't despair. MATTHEW WALKER: There's
hope on the way. Trust me. MATT BRITTIN: Yeah, well,
I think what I'd like to do is start with just
the basic question. What is enough sleep? And what goes wrong when
we don't have enough sleep? MATTHEW WALKER: So
right now, we recommend somewhere between seven
to nine hours of sleep. The sweet spot is probably about
eight for most human adults. How do you know if you're
not getting enough sleep is one of those questions. Several things-- firstly, if
you are setting an alarm-- by the way, I'm
going to probably just look at you, Matt. Because I know there's
this strange thing that happens with an audience
where you're sort of I'm not [STUTTERING]. MATT BRITTIN: You
can try, but you may want to divert your attention. MATTHEW WALKER: 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. MATT BRITTIN: Right. MATTHEW WALKER:
And in fact, when we've studied 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. Why would you stop something
that hasn't yet completed? 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 10% to 15%. There, based on our estimates,
it's about 1% to 2%. They just don't
understand the concept of not being able to sleep. So there's something
about modernity that's desperately dislocated
us from this thing called a good night of sleep. MATT BRITTIN: Right. And so let's just
talk for a minute. So a lot of what you
cover in the book and that you've covered
in your research is the health issues that
arise from lack of sleep. So just tell us. Let's start with
the worst, right? So what happens to you
cognitively, fitness-wise, illness-wise,
attractiveness-wise. What are the things that happen? MATTHEW WALKER: Let me
start with attractiveness. So we've all heard of this
thing called beauty sleep. It's this 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. And 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. MATT BRITTIN: That's
after one night. MATTHEW WALKER: After one night. So there is objectively a
thing called beauty sleep. And people independently can
see it, which is no surprise. Because 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. How do you know that? Because it turns
out that there are-- MATT BRITTIN: You can
read people really well. MATTHEW WALKER:
--clear facial cues and bodily cues that
express this thing called insufficient sleep. And other human beings
can pick up on it. MATT BRITTIN: Right. So thing one-- you
get less attractive. 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? MATTHEW WALKER: So if
you're not sleeping, one of the first things
that you become deficient in is your capacity to learn. So we've done studies
where we'll, 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 its ability to lay
down new memory traces | it is underslept. And 40% is non-trivial. That's the difference
between acing an exam and failing it miserably. And I think that's
particularly concerning for sleep in our education
populations 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. 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 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, controlling decisions. And it keeps our
emotional brain in check. But when you're sleep
deprived, the first part of the brain to take a nosedive
like a dart into the ground is your prefrontal cortex, which
unleashes your emotional brain. And so we see that the amygdala
is about 60% more reactive under conditions of
sleep deprivation. And what's interesting is
that it's pendulum-like, that you are not only
more negative in terms of your responses,
you're also much more likely to be more reward-seeking
and more sensation-seeking. So the emotional
distance within which you travel when you are sleep
deprived is vastly larger. So you become more
emotionally irrational, as well upstairs in the brain. 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 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. 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 because it's made out of these
cells called glial cells. 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. Because wakefulness is
low-level brain damage. One of the sticky toxic proteins
that it washes away at night is a protein called
beta amyloid. 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. MATT BRITTIN: And this is
like taking the plaque out of the brain, effectively. MATTHEW WALKER: Exactly. So it's essentially good
night's sleep clean, in that sort of sense. MATT BRITTIN: And I read-- so
I was going to ask you about this-- I read that you got
into this whole area way back when you were actually
looking at Alzheimer's and trying to understand
why Alzheimer's seemed to lead people to sleep less. But actually, you realized that
it was the other way around, that it was sleeping less
that was contributing to the Alzheimer's. Is that how it worked out? MATTHEW WALKER: Yeah. So I think we're all accidental
sleep researchers in the field. No one, when they're a child
and you go around the classroom, and the say, what would you
like to be when you grow up, no one says, I'd love to
be a sleep researcher. And I fell into it by accident. During my PhD, I was trying
to use brainwave patterns to diagnose people with
different types of dementia very early on. And I was failing miserably
for the first couple of years. And I used to go home. And I have this little igloo
of journals in my room. And I'd read them
at the weekend. And then, one weekend, I
realized, reading an article, that, in some dementias,
like Alzheimer's, the centers that generate sleep
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, 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. 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? And now, 20 years later, that's
exactly what we're finding. MATT BRITTIN: And that's
what you're working on, or some of the things
you're working on, in your Center
for Sleep Science? MATTHEW WALKER: Yeah. So we do a huge amount
of work with aging and Alzheimer's disease. We know that a psychological
signature of aging is that our memory gets worse. But a physiological
signature of aging is that our sleep gets worse. And only recently we
published evidence that those two things are
not simply co-occurring. They are significantly
interrelated. And what's exciting-- or that
may sound very depressing, that it's in the mail. It's coming at you. 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 or even the vasculature
of the brain-- those are fiendishly
difficult to treat. 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. MATT BRITTIN: Right. Because am I right in
saying it gets harder to sleep as you get older? What changes, exactly? MATTHEW WALKER: Yeah. So one of the myths is that
older adults need less sleep. 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. MATT BRITTIN: Right. OK. Wow. So you've covered a lot there. But you haven't covered 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. MATTHEW WALKER: Yeah. So we've spoken a little
bit about the brain. Let me speak a little
bit about the body. I think the best place to
start there is testicles-- [LAUGHTER] --because why wouldn't you? MATT BRITTIN: That's
what I always say, yeah. Why not? MATTHEW WALKER:
So what we know is that men who sleep
five hours a night have significantly smaller
testicles than those who sleep seven hours or more. In addition, men-- MATT BRITTIN: That's
relevant because? MATTHEW WALKER: Well-- [LAUGHTER] --struggling to come up
with an answer to that one. MATT BRITTIN: Is it
to do with fertility? MATTHEW WALKER: Well,
what's also interesting is that if you look
at the sex hormones, 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. MATT BRITTIN: Wow. MATTHEW WALKER:
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. So if you end up
having a couple that's trying to start a family,
and they're both underslept, it's actually much
more difficult to try and develop a genetic
legacy in that regard. MATT BRITTIN: Wow. OK. So in terms of sleep effect on
the body, reproductive health. MATTHEW WALKER: Reproductive
health is the first one. I think the next one
I would speak about is sleep and
cardiovascular disease. The links there between a
lack of sleep and heart attack and stroke, hypertension,
are incredibly strong. I'll give you just one example. Here, you don't need a whole
night of sleep deprivation. All it takes is one hour. Because there is a
global experiment performed on 1.6 billion
people across 70 countries twice a year. And it's called
daylight savings time. MATT BRITTIN: Right MATTHEW WALKER:
Now, in the spring, when we lose an
hour of sleep, we see a subsequent 24%
increase in heart attacks the following day. MATT BRITTIN: Wow. That's astonishing. MATTHEW WALKER:
But in the autumn, when we gain an
hour of sleep, we see a 21% reduction
in heart attacks. MATT BRITTIN: It's incredible. MATTHEW WALKER: So
that's how, I think, fragile our bodies are
to even the smallest perturbation of sleep. And by the way, you see
exactly that same profile around daylight savings time
for road traffic accidents, for suicide rates. You can even see
this, by the way, in federal judges
and their sentencing that on that Monday after
losing one hour of sleep, the federal sentences
are far more harsh, whereas in the autumn, if
you get your sentencing, you actually get a
more lenient sentence. MATT BRITTIN: That's incredible. MATTHEW WALKER: You
can see it all over. And that's just one
hour of lost sleep. MATT BRITTIN: And I know you
talk about the time of day that education starts. And you also talk
about road accidents in the context of sleep, two
really big social issues. So road accidents--
you're claiming here that sleep's a bigger
killer than alcohol or drugs in road deaths. Tell us why that is. MATTHEW WALKER: So when
you are underslept-- if you're severely
sleep deprived, you can typically fall
asleep at the wheel. But that's usually
not what happens. Most people are
chronically underslept. They're trying to survive on
six hours of sleep or less. And what you typically
then have are what are called microsleeps
where your eyelid will just partially close, and the
brain essentially just goes to sleep for a second or two. MATT BRITTIN: Right. MATTHEW WALKER: Now, if you're
traveling at 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,
which means that you could be on incoming traffic. That's the first issue. The second reason that drowsy
driving is usually much more fatal in terms of it's damaging,
in terms of car crashes, is the following. When you're drunk
or you're high, you typically react too late. MATT BRITTIN: Right. So reactions are slowed down-- MATTHEW WALKER: Slowed down. MATT BRITTIN: But
you're reacting. MATTHEW WALKER: But
you're reacting. MATT BRITTIN: Right. MATTHEW WALKER: When
you are sleep deprived, you don't react at all
because you have a microsleep. 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
drink driving or drugs. MATT BRITTIN: That's
an amazing insight. And then on education,
as a father of teenagers, I know this, the hour at
which we start the school day and how that
changes, particularly if somebody's growing up
from childhood through teens, our sleep needs seem to change
in that period, as well. Tell us a little bit
about that and the impact that you've identified there. MATTHEW WALKER: I think
this is a real problem that we've consistently started
to roll back education times. It's better here in
the United Kingdom than it is in the United States. But I know that there was a
push recently in the government level to try and delay
school start times until 10 o'clock in the morning. 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, that
we move forward in time. We want to go to bed later,
and we want to wake up later. MATT BRITTIN: Why would that be? Do you know why that is? MATTHEW WALKER: So
we know the biology, and we know why it's
happening from a sort of a mechanistic standpoint. From an evolutionary standpoint,
that's an interesting question. I think one of the
things that I posit in the book is that that's
the moment in time when you need to cut the cord
from parental influence. You need to 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. What better way to do
that than actually, now, going to bed later
than your parents? But yet your cohort, your
brethren of that age, are also staying up later. 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. MATT BRITTIN: So my
teenagers aren't lazy. They're just natural. MATTHEW WALKER: They're
just doing simply what their biology does. And that's one of the
problems is that we have-- sleep has a terrible
image problem in society, that we label people who
get sufficient sleep as slothful or even lazy. And I noticed that
when you said, what about the people who get
nine hours of sleep or more? And I see this all the time. These hands, these
shamed hands go up. Yeah, yeah. 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. And they'll sidle up to
me, and they'll say, look, 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. MATT BRITTIN: We should
be cheering them on? MATTHEW WALKER: We should be
celebrating them and embracing sleep. And we don't do that. And what's strange
is none of us look at an infant sleeping
during the day and say, well, what a lazy baby. Because we know at
that time of life, sleep is absolutely essential. But if you look at the data
now, worryingly, somewhere between infancy
and even childhood, we abandon the notion
that sleep is important. And instead, we label it with
these negative connotations. And so I think one
of the problems is that school start
times are too early. Based on some data
that we've looked at, children of all ages,
from five to 18, are now sleeping two hours
less in this modern era than they were 100 years ago. To put that in context, if
I went to my ethics board and said, look, I'd love
to take a group of seven and eight-year-olds,
and I'd like to deprive them of sleep for
two hours every single night for the next month and
study them, is that OK? they'd probably put me
on academic probation, and rightly so. MATT BRITTIN: Yeah. That's what the world's done. MATTHEW WALKER: But yet that's
exactly what the world has done now across years of their life. MATT BRITTIN: That's amazing. So we could spend a long time
talking about bad effects of not enough sleep. Let's talk a little bit about
the causes and then what you can do to improve, if we can. So you alluded to it there. One of the causes
is, obviously, light, artificial light allowing us
to extend the waking hours. But what causes bad sleep? What are the kinds of things
that make us sleep badly today? MATTHEW WALKER: So I think
it's important to separate out two things. One is having problems
with sleeping. The other is having the
opportunity to sleep. 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, 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. Nobody wants to short-change
their TV time or their family time. So the one thing that gets
squeezed like Vise-Grips in the middle of the
night is this thing called a normal
eight-hour sleep period. Then we've also spoken
about the stigma, 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 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 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're much closer
to Russian time than you are UK time if
you're reading an iPad for one hour before bed. MATT BRITTIN: Wow. MATTHEW WALKER: 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,
particularly blue light is a harm. But that's not the only issue. I think technology is--
and I'm mindful, of course, of where I'm speaking-- but one of the things
that technology can cause is just anxiety 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
hit your pin code and the tsunami of the
world just invades you. And you train your brain to
expect that every morning. It's called
anticipatory anxiety. And it lightens your sleep. It prevents you from going
into the deeper sleep. So the advice there
would be try to see if you can abstain
from opening your phone until after you've
brushed your teeth. MATT BRITTIN: Yes. There's a great advice, which
is if the first thing you touch in the morning is your
phone and not your partner, you're in trouble. MATTHEW WALKER: That's right. Yeah. And that is not going
to be a partnership that will last for too long. MATT BRITTIN: Pay
attention, folks. MATTHEW WALKER: And
then just scale it back. Say could I not look at my
phone until I've had breakfast? And there's something
so sublime about just going into a state of
non-technologically invaded consciousness in the
first five or 10 minutes. If you can't do
that, you probably need 20 minutes of delay
time rather than 10 minutes. So I think that's another
problem, which is technology. We also know just general
stress and anxiety. That's the principal
cause of insomnia. So now we're
shifting from things that are shortening your
sleep duration to things that are preventing your sleep. So we are a
dark-deprived society. We need that darkness at night. So trying to stay away from
screens in the last hour before bed. Also dimming down the
lights in your home. Drop the lights by 50%. You'll be surprised at how
soporific that actually is. I think one of the other
aspects above and beyond stress, which is a key thing
triggering insomnia, is alcohol and caffeine use. MATT BRITTIN: Yeah. MATTHEW WALKER: So this usually
makes me deeply unpopular when I describe. I'm generally unpopular but this
makes me even more unpopular. Firstly, caffeine. Caffeine, everyone
knows, keeps you awake. It's an alerting substance. It's the only psychoactive
drug that we readily give to our children
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 that
caffeine is gone by 6:00 PM. But it means that
there's still a quarter of that caffeine swilling around
in your brain at midnight. MATT BRITTIN: That's amazing. MATTHEW WALKER:
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. MATT BRITTIN: So what's the
latest I can have my coffee? MATTHEW WALKER: I would scale
back 14 hours before bed. MATT BRITTIN: Wow. MATTHEW WALKER: Really? MATT BRITTIN: Can I have
a lot of coffee early? MATTHEW WALKER: So you can
strategically drink caffeine to help wake you up. But if that's the case,
if you're using caffeine before midday, you're probably
self-medicating your state of chronic sleep deprivation. MATT BRITTIN: OK. If you're using it early
then you're self-medicating. If you're using it
late, then you're causing yourself a problem. MATTHEW WALKER: That's right. MATT BRITTIN: Do
you drink coffee? MATTHEW WALKER: I'm
decaffeinated all the way, which is not really-- it's not that bad in terms of-- MATT BRITTIN: Let's
take this all at once. Come on. Bring on the alcohol. Bring on the alcohol. MATTHEW WALKER: So there's
only one other thing I'll say about caffeine. Even if you're someone
who says, well, I can drink a cup of coffee in the
evening and I fall asleep fine, and I stay asleep,
so I'm unaffected, that's not actually true. We've done some studies where
we give you one single dose of caffeine, which is
about 160 milligrams-- standard cup of coffee-- and then we measure
your sleep that night. And typically, what you have
is about a 20% reduction in the amount of deep sleep as
a consequence of that coffee. To put that in
context, I would have to age you by about
20 to 25 years to drop your deep sleep by 20%,
or you could do it every night with a cup of coffee. MATT BRITTIN: Wow. So alcohol, although it
helps us to go to sleep, has a similar effect on the
quality of sleep, doesn't it? Are you going to
tell us how bad? MATTHEW WALKER: So it actually
doesn't help you fall asleep. MATT BRITTIN: It doesn't? MATTHEW WALKER: So
alcohol is a sedative. And sedation is not sleep. But when you have a nightcap,
you mistake the former for the latter. So it helps you lose
consciousness more quickly. MATT BRITTIN: I'm feeling
this is personal now. MATTHEW WALKER:
Yeah, yeah, I know. Maybe I should start
looking at the audience rather than at Matt. So yes. You think that you're
falling into sleep. What you're doing is you're
just knocking out your cortex. The second problem with alcohol
is that it fragments your sleep so that you will
wake up many more times throughout the night. So you have broken sleep. And that leads to,
then, the next morning you'll feel unrefreshed
and unrestored by your sleep,
which, by the way, usually leads you to then
reaching for two cups of coffee rather than one. And it's a vicious cycle. And then you need
something to get you down at night, which is
typically a nightcap. And it's a vicious cycle. The third problem
with alcohol is that it's very good at
blocking your dream sleep, your rapid eye movement sleep. So on all of those grounds,
alcohol is best to be avoided. MATT BRITTIN: So I want to come
to questions from all of you in a couple of
moments, if I may. But before we do that, let's
just talk a little bit more. You've alluded to,
there, why we sleep, which is the whole
title of your book and the huge benefits to
our health and well-being from sleeping well. But what actually
happens during sleep? 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? MATTHEW WALKER: So let
me tell you a little bit about how sleep works
and then what it does. 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-- unimaginatively called
stages 1 through 4, increasing in the
depth of sleep. So stages 3 and 4 of
non-REM are the deep stages of dreamless sleep. MATT BRITTIN: Dreamless. MATTHEW WALKER: Dreamless. MATT BRITTIN: That's when
the body's mending itself? What's happening
in those states. MATTHEW WALKER: It is
one of the times, one of the stages,
where the body goes through a remarkable
restoration. We see protein synthesis. We see rebuilding of cells. 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. 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. Another demonstration of this
is if you get a flu shot, and we'll be four months
away 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 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. MATT BRITTIN: These
are massive numbers you're quoting here
in terms of the impact of these things-- huge. MATTHEW WALKER: Yeah. And why is that? Why can I quote
such large numbers? Is it just a lot of
hand waving and plucking of 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 to risk mitigate
this when it happens. Now, there is precedent
in biology for that. Why can't we, for example,
bank sleep and then use it when we're going
to be sleeping 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 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? MATT BRITTIN: Oh, you
should invent that. MATTHEW WALKER: I would love. I would make so much
money out of it. But the reason it doesn't
exist is because we've never had that challenge. Humans are the only
species that do that. MATT BRITTIN: It's amazing. So you were talking,
then, about non-REM sleep and the going deeper and deeper. MATTHEW WALKER: 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. MATT BRITTIN: Right. So the REM sleep you
haven't touched on. So tell us a bit about that. That's when we're
dreaming and [INAUDIBLE].. MATTHEW WALKER: 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. MATT BRITTIN: So some
parts of your brain are more awake than
when you're awake. MATTHEW WALKER: That's right. They're more active
when you're in REM sleep than when you're awake. Other parts of the brain,
however, switch off. MATT BRITTIN: Because we
parallelize ourselves, don't we? MATTHEW WALKER: We do. So when you go into dream sleep,
which is rapid eye movement sleep, the brain essentially
paralyzes the body so the mind can dream safely. It stops you acting
out your dreams. So every time you
go into dream sleep, you are locked down into an
incarceration of the body. You cannot move. You can't speak out. And that's a safety mechanism. As we get older, in some
people, particularly males, that part of that lockdown
of the body begins to fail, and you start to
act out your dreams. It's called REM sleep
behavioral disorder. But for the most part, most
of us are not doing that. MATT BRITTIN: I'm
worrying about that now. MATTHEW WALKER: It's
a 90-minute cycle. MATT BRITTIN: How old do
you have to be for that? MATTHEW WALKER: It usually
starts in people in their 50s. MATT BRITTIN: Oh, dear. OK. [LAUGHTER] MATTHEW WALKER: And one
of 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, your disease risk 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. What we need to have is a
model of truly health care. If you do that it's a
model of prevention, not a model of treatment. And if you can find things that
are foretelling your disease risk way ahead of time, you give
yourself the opportunity window to do something about it. 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
protective or predictive. MATT BRITTIN: When I was reading
about REM sleep in your book, you mentioned not just the fact
that some parts of our brain are more active but also
that we're replaying the days memories at 20X normal speed. And there's a theory that
we're defragmenting and filing in that sleep. But what really is
going on in REM sleep? MATTHEW WALKER: So in
the studies with rats, what they've done is they've
had them run around a maze, and they've put
electrodes in the brain. And you can pick up this
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 brain cell firing as its coding the maze. And it sort of goes up
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 [WHIRRING]. MATT BRITTIN: So it
literally is happening. That's incredible. MATTHEW WALKER:
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
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 learned 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. 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? But REM sleep is almost like
a Google search gone wrong. It's during REM sleep that
you input your search term, and it immediately takes
you to page 20, which is about some bizarre thing. You think, hang on a second. Is there a really-- but there's a strange,
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 previously impenetrable problems. That's what dream sleep
seems to be about, as well. MATT BRITTIN: Wow. It's incredible to understand
just the beginnings of that and how it works. And so I'd like to invite
people to come to the mic. We have our first
questioner here. Do you want to speak up
and find out about sleep? AUDIENCE: Just a quick
[INAUDIBLE] this is working. Yes. Do you have any tips on
dealing with jet lag? So anything we
can do to improve? MATT BRITTIN: So our
bodies were never designed to be fast forwarded
through time with this thing called a jet engine. 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. 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, most people on that
flight over from San Francisco are probably going to be
sleeping in 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 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 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 11:00. 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. And then, if you want
to, you can strategically use melatonin. It's not available
over here, but it's available in other countries. Usually take that about
an hour before bed. Most people dose too much. They usually do 5
to 10 milligrams. It should really be
0.5 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. AUDIENCE: Thank you. MATT BRITTIN: It's a mine field. Great tips. And actually, one other
thing while you're on the subject of travel,
because quite a few of us do, is sleeping somewhere
unfamiliar also has an impact on your sleep. Just tell us a
little bit about that because it's also
useful for this group. MATTHEW WALKER: It is. So you will sleep 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, wouldn't it be lovely
if we could do that? You could keep working, and one
half of your brain is sleeping, and then it switches over. But humans, actually, we didn't
think they could do that. But they have 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 trying to keep watch and maintain some
degree of vigilance. And that's probably the
reason why a lot of people will say that first
night in the hotel-- MATT BRITTIN: You never
feel as good, yeah. MATTHEW WALKER:
--never feels good. I never quite sleep. Or this phrase, I can't wait
to get back to my own bed. In some ways, it's familiarity. In other ways, it's the
depth of your sleep, as well. MATT BRITTIN: Truly fascinating. Next question. AUDIENCE: Hi, Matthew. 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. MATTHEW WALKER:
Well, it's actually the lack of sleep that's taking
the life out of you right now. [LAUGHTER] But let's not rush to judgment. Let's see what we can do before
we make that classification. AUDIENCE: And I
suppose my question is I try to sleep
when I can, and I try and catch up as
much as possible. But I'm not getting as much
as I need in this period. When I get through
this, how is my health going to be in, say, a year
or two, when I've caught up and they're sleeping
through the night and all that kind of stuff? Are there long-term effects. You mentioned the sleep bank. I recognize you
can't bank sleep. But can you catch up once you
start sleeping well again? MATTHEW WALKER: Great question. So I think parenting--
immensely difficult. You're doing the right
thing in the sense of being opportunistic about your sleep. Get it when you can. At that stage, you're going
to be chronically underslept. Also trying to help kids,
as well, one of the things is routine. That can really help them. Just find a routine
that works and then stick to it religiously. Also, for kids, taking
toys out of the bedroom is a recent finding
that that actually means that the bedroom is
this thing other than sleep, and toys become a
trigger, and they actually sleep worse when they've
got toys in the bedroom. So get those out, as well. Do something calming
and relaxing with them in the hour before bed--
typically, reading, doing a puzzle. Hot baths are a great thing--
great thing for all of us. And the reason is because you
need to drop your core body temperature by about 1 degree
Celsius to initiate sleep and then to stay asleep. It's the reason
that you will always fall asleep easier in a room
that's too cold than too hot. But what happens-- and you
think, well, hang on a second, you're telling me to take a
bath, doesn't that warm me up? It's actually the opposite. When you get into a bath or you
bathe a child, all of the blood rushes to the surface. And when you get out of
the bath, all of the heat is radiated out of the body. So your core body
temperature actually plummets, which means that you
fall asleep faster and stay asleep. So trying to help
kids sleep better will ultimately help
you sleep better. But to come to your question,
yes, sleep is not like the bank that the damage that is
happening is happening, and you can't necessarily
reverse that damage. However, it is never too late
to start sleeping better. And when you start
sleeping better, your health outcome
will stabilize. And I'm not just saying
that to be optimistic. We know the data. For example, there's
a study where we looked at people who had
untreated sleep apnea, which is snoring. And by the way, if anyone
listening is a snorer or they know of
someone who is snoring, go and get their doctor to
do a sleep test on them. Sleep apnea, which
is heavy snoring, is a killer in
terms of a disease. And 80% of people who
have it are undiagnosed. So these people had
sleep apnea, and they were given a treatment,
which is this face mask to help open up their airway. Turned out that about
half of the people adhered to the treatment. The other half didn't. And then you track them
for 10 or 15 years. What you find is that
those people who adhered to the treatment, whose
sleep improved-- now, these were people in their 50s-- once they started
sleeping better, they staved off the onslaught
of Alzheimer's disease by almost 10 years relative
to that other group, who didn't comply to the
treatment and, therefore, continued to sleep badly. It is a causal piece of evidence
that even in mid to later life, if you correct your sleep you
improve your long-term health outcome. AUDIENCE: Thank you. MATTHEW WALKER: You're welcome. MATT BRITTIN: Trouble
is, of course, when your kids are a year
older, you've still got all of the next 15 years to go. [LAUGHTER] MATTHEW WALKER: Good luck. Sleep well. MATT BRITTIN: How many people
currently got young children. So we've actually quite a lot
of very sleep-deprived people in the room. MATTHEW WALKER: Yeah. The nice thing is all of the
frightening and terrible and damaging things that
I'm telling you, you won't remember any
of these because you're so insufficiently
slept that you'll wake up tomorrow
morning, you'll think, ah, everything's just fine. You won't worry. Yes. MATT BRITTIN: Time for
a couple more questions. AUDIENCE: Hi, Matthew. First of all, thank you for
an absolutely fantastic book. You've got a fan for
about a year and a half. And I think everybody
should read it. The one question I've been
struggling to answer to myself is when do I know that
I've had enough sleep? And one thing that wasn't
clear to me from the book is I think there is this
proverbial waking up, opening the window, dancing in the
street, everything is great, I've had a good night's sleep. I haven't had that
in the past 10 years, and I doubt many
people here have. What I find is I
wake up on Saturday. I don't set the alarm. But then I roll in bed
for a couple of hours. There's this weird half-slumber. I kind of drift in
and out of sleep. When do you actually
know that it's time to get out of bed, without
setting your alarm, supposedly? When would you do that. MATTHEW WALKER: Yes,
it's a great question. It's very difficult to
figure that out just at the weekend because at the
weekend, what you're doing is you're trying to
sleep off the debt that you created
during the week. And this is why most people
will often say to me, well, when I sleep late
during the weekend, sometimes I feel worse. It's almost like I
go to sleep hangover. So there's this thing called
too much sleep, and it's bad, and I shouldn't be
sleeping as much. No, what you're doing
there is you're just having a hangover because
your brain is trying to get what we call recovery sleep. And it will still
feel heavy on you. So what you need to do
is an experiment where if you can structure your
work schedule, you just say, I am not going to set an alarm. And I am just going to let
my sleep unfold naturally. Now, to begin with,
the biggest fear is that you're
going to oversleep, and you're going to
turn up to work late. And that may happen for
the first couple of days. But gradually,
what will happen is that you will sleep
off some of that debt, even though you can't
make it all back, and you will throttle back,
and you will find a sweet spot. And then you will just
start waking up naturally. One of the issues you have
to ask yourself, though, is when am I designed to sleep? And it's called your chronotype. So everyone here
has a chronotype. Are you a morning type? Are you an evening type? Are you somewhere in between? It's what we call
owls and larks. Now, you don't get
to decide that. It is genetically hardwired. It's gifted to you at birth. There is no choice. How do you figure out
what type you are? Well, if you were
to be on a desert island with no commitments,
no one to wake up for, just ask yourself, what
time would I probably like to go to bed, and what
time would I probably like to wake up? That's probably your chronotype. When you sleep in sync, in
harmony, with your chronotype, that's when you get the
very best quality of sleep. If you sleep in a mismatched
fashion with your chronotype, you won't get good sleep, and
you will struggle with sleep. A good example of
this is night owls who would like to go to sleep,
let's say, at midnight or 1:00. They will often come
to me saying, look, I've got terrible insomnia. I lie in bed for
the first two hours, and I just can't fall asleep. And I'll say, well, what
time are you going to bed? And they say, I go
to bed at 10 o'clock because I have got
to be awake at 6:00. Well, there, you're
two hours early relative to your natural,
biological edict. And so no wonder
you're going to be lying in bed awake for
the first two hours. Because your body is not yet
ready to generate the sleep that it needs. And it masquerades as insomnia. You don't have insomnia. You just have a
mismatch between when your biology wants
you to sleep and when you're trying to sleep. So finding out what
your chronotype is and then finding how to
match that with your sleep is the best chance
for good sleep. MATT BRITTIN: You also
suggest, don't you, regular pattern, so trying to
go to sleep at the same time and get up at the same time. This whole idea of
weekend recovery doesn't really cut it for you. MATTHEW WALKER: No, it doesn't. And what people typically
do at the weekend, they will sleep in by, maybe,
two or even three hours, and they'll be staying up later. And then, come
Sunday night, you've got to drag your biological
clock all the way back by two or three hours. MATT BRITTIN: Makes
Monday even worse. MATTHEW WALKER: And
it makes Monday worse. And we actually see that
in terms of productivity, this sleepy Monday effect
is what we call it. But one of the problems
there is that that's torturing your biology. It's essentially like flying
back and forth from Moscow to London every single weekend. And your body does
not respond to that. And that's the
reason that when we see in people who do night shift
work that their disease risks are astronomically higher. In fact, the link between
a lack of sleep and cancer has now become so strong that
the World Health Organization has classified any form
of nighttime shift work as a probable carcinogen. MATT BRITTIN:
That's astonishing. So you don't want to do
shift work, basically. MATTHEW WALKER: No. And you don't want
to create what's called social jet lag,
which is artificial shift work, by sleeping in late, going
to bed late at the weekend. Just try and keep it
regular is the best advice. MATT BRITTIN: Party
early, people. OK. AUDIENCE: Amazing. Thank you so much, Matthew. I really enjoy your talk. I see that you are
wearing Oura ring. Do you have recommend this
device as to track sleep? And my second question-- sorry
about that-- is how do we take naps more effectively? Because we have so many
napping pods in office. MATTHEW WALKER: Yeah,
two great questions. So I am wearing an Oura ring. I don't have any affiliation
with the company. I've tried out just about
every sleep tracker out there. I love technology. What I would say
right now is most of these sleep
trackers are probably much of a muchness in terms
of the accuracy of separating non-REM sleep from REM sleep
from light sleep, deep sleep. So I wouldn't get too hung up
if these devices are telling you you're having very
little deep sleep. If I brought you
into my laboratory, the accuracy there would
be the truth-telling thing. I think one of the interesting
things about sleep trackers, though, is the form factor. When we go to bed,
we take things off. We don't put things on. So I'm actually very enamored
right now with this idea that I would term
unwearables for sleep rather than wearables for sleep. And so I think putting
things on your head, putting things on your wrist,
strapping things to your chest, I think those
things are probably not going to result in a
great deal of stickiness. I think the ring is probably the
second-least intrusive thing. I think the best device,
ultimately, is probably going to be the bed itself. You think about
your car nowadays. It's packed full of sensors. It's remarkably
technologically capable, whereas 60 years ago, your
car was very rudimentary. Well, think about your mattress. Your mattress now, 60 years
on, is pretty much the same as it was 60 years before. Why isn't it packed full
of just as many sensors and tracking the
health of you as much as your car is being
tracked in terms of its own mechanical health? So I think if you were to ask me
to rank order which devices are ultimately going to be the
best for tracking sleep, I think probably the mattress
is going to be the best one. There, you can fall
into bed drunk, and you'll still get your sleep
measured, where you don't have to worry about charging it. MATT BRITTIN: And just
one minute on napping. MATTHEW WALKER: Yes. So naps can be a benefit. We've done some
studies with naps. They can provide improvements
for both brain and the body. You can get your
eight hours of sleep by way of sleeping one long
bout at night and then a nap, like siesta-like behavior. In fact, when we've looked
at hunter-gatherer tribes whose way of life hasn't
changed for thousands of years, they have biphasic sleep. They sleep from about
9:00 to about 5:30, 6:00, and then they have this
siesta-like behavior. By the way, have you ever
wondered what the term midnight actually means? The middle of the night. And in those cultures, that's
exactly what it is for them. But for us now,
in modernity, it's the last time we check
email or we think about posting that last thing. But I think the point here is
that naps can be beneficial but with a big caveat, which
is that if you are struggling with your sleep at night,
do not nap during the day. Because it comes back to
that sleepiness signal. As you're awake
across the day, you're building up all of that
healthy sleepiness. And when you sleep,
you remove it so that you wake up
feeling refreshed. But if you take a
nap in the afternoon, you release some
of that sleepiness, and it can make it harder to
fall asleep or stay asleep at night. So if you are not
struggling with sleep and you can nap regularly,
naps are just fine. AUDIENCE: Awesome. Thank you so much. MATT BRITTIN: We are
pretty much out of time, so I'd like to just ask
a closing questions, so a quick answer
from you, if I may. So lots of advice on how we can
sleep better and look after our sleep better. So what are the top
things that we should all be doing and
thinking about if we want to have better
health through sleep? MATTHEW WALKER: So I think
we've touched on many of them. Regularity is king-- go
to bed at the same time, wake up at the same time. Get your darkness
in the evening. That's critical. Drop your bedroom temperature. Get it cold, so you
can initiate sleep. Probably about 18
degrees Celsius is optimal for the
sleep of most people. It sounds cold. MATT BRITTIN: It's quite cold. MATTHEW WALKER: But
put thick socks on. Have a hot water bottle
at the end of the bed. That's fine, but
cold it must be. And we've spoken about
alcohol and caffeine, so I'll dispense with those. The last thing I would say
is do not lie in bed awake for very long. So if you haven't fallen
asleep after 15 or 20 minutes, or if you haven't fallen back
asleep after that same period, don't stay in bed. Get out of bed. Go to a different room. And in dim light,
just read a book. An only return
when you're sleepy. And the reason is that your
brain is so associative that it will very quickly
learn that your bedroom is the place of being awake
rather than being asleep. And you need to break
that association. And so by coming back
only when you're sleepy, you will relearn the connection
that your bedroom is the place of sleep, not about wake. So you would never
sit at the dinner table waiting to get hungry. Why would you lie in bed
waiting to get sleepy? And the answer is you shouldn't. MATT BRITTIN: And so
since you were the person to mentioned
testicles, is it still OK to do other bedroom
activities in the bedroom? MATTHEW WALKER: That's the
one exception to the rule. MATT BRITTIN: Oh, great. MATTHEW WALKER: Yep. Intimacy and sleep, they're
both fine for the bed. MATT BRITTIN: Oh! Let's end on that note. Thank you very
much, Matt Walker. MATTHEW WALKER: Thank you. [APPLAUSE]
