[MUSIC PLAYING]
JOSH: Right.
And thank you all for coming.
This is a great crowd.
And I want to welcome
Dr. Matthew Walker.
He is professor of
neuroscience and psychology
at the University of
California, Berkeley.
And he's the
founder and director
of the Center for
Human Sleep Science,
and he's here today to
talk about his new book,
"Why We Sleep."
So without further ado.
MATTHEW WALKER: Thank
you very much, Josh.
[APPLAUSE]
Thank you.
Well, it's a delight and
privilege to be here.
And I would like to
start with testicles.
[LAUGHTER]
Men who sleep five
hours a night have
significantly smaller
testicles than those
who sleep eight hours or more.
In addition, men who routinely
sleep five to six hours a night
will have a level
of testosterone
which is that of someone
10 years their senior.
So a lack of sleep
ages you by a decade
in terms of that aspect, that
critical aspect of wellness
and virility.
And we see equivalent
impairments
in female reproductive health
caused by a lack of sleep.
This is the best news
that I have for you today.
[LAUGHTER]
From this point forward,
it's only going to get worse.
Rather than tell you about the
wonderfully good things that
happen when you get
sleep, I'm going
to tell you about the
alarmingly bad things that
happen when you don't get
enough both for the brain
and for the body.
Let me start with the brain
and the functions of learning
and memory.
What we've discovered over
the past 10 or so years
is that you need sleep after
learning to essentially hit
the Save button on
those new memories,
so that you don't forget.
So sleep essentially
future-proofs
those facts within the brain.
But recently, we've discovered
that you not only need sleep
after learning, you also need
sleep before learning, but now
to actually prepare your
brain, almost like a dry sponge
ready to initially soak
up new information.
And without sleep, the
memory circuits of the brain
effectively become
waterlogged, as it were,
and you can't absorb
new information.
So here in this
study, we decided
to test the hypothesis that
pulling the all-nighter
was a good idea.
How do you do that?
Well, we took a group
of healthy adults
and we assigned them to one of
two experimental conditions--
a sleep group and a
sleep deprivation group.
Now, the sleep
group, they're going
to get a full eight
hours of shuteye.
But the deprivation
group, we're going
to keep them awake
in the laboratory
under full supervision.
There's no naps,
there's no caffeine.
It's miserable for everyone
included, us as well.
And then the next
day, we're going
to place those participants
inside an MRI scanner,
and we're going to
have them try and learn
a whole list of new facts
as we're taking snapshots
of brain activity.
And then we're
going to test them
to see how effective
that learning has been.
And that's what you're looking
at here on the vertical axis,
the amount of learning.
So the higher up you are,
the more that you learn.
And when you put those
two groups head to head,
what you find is a quite
significant 40% deficit
in the ability of
the brain to make
new memories without sleep.
And I think this
should be frightening
considering what we
know is happening
to sleep in our education
populations right now.
Just to frame this
in context, it
would be the difference
between acing an exam
and failing it miserably.
And we've gone on
to discover what
goes wrong within your brain to
produce these types of learning
disabilities.
There is a structure on
the left and the right side
of your brain called
the hippocampus.
And you can see it here in these
sort of orange-yellow colors.
Think of the hippocampus
like the informational inbox
of your brain.
It's very good at
receiving new memory files
and holding on to them.
And when we looked
at this structure
in those people who'd had a full
night of sleep here in green,
we saw lots of healthy
learning-related activity.
Yet in those people who
were sleep deprived,
we actually couldn't find any
significant signal whatsoever.
It's almost as though
sleep deprivation had
shut down the memory inbox
and any new incoming files,
they were just being bounced.
You couldn't effectively commit
new experiences to memory.
And parenthetically,
I should note
if you would like
to know what life
is like without a
functioning hippocampus,
just watch the movie "Memento."
I suspect many of
you have seen this.
But this gentleman
suffers brain damage.
And from that point
forward, he can no longer
make any new memories.
He's what we call
densely amnesic.
The part of his brain that was
damaged was the hippocampus,
and it is the very
same structure
that sleep deprivation will
attack and block your brain's
capacity for new learning.
So that's the bad that happens
when you take sleep away.
Let me just come back to that
control group for a second.
Do you remember those
folks that got a full eight
hours of sleep?
Well, we can ask a very
different question here.
What is it about the
physiological quality of sleep,
when you do get it, that
actually enhances and restores
your learning and memory
ability each and every day?
And by recording sleep
with electrodes placed all
over their head, we've
discovered that there
are big, powerful brain waves
that happen during the very
deepest stages of sleep that
have, riding on top of them,
these spectacular bursts
of electrical activity
called sleep spindles.
And it's the combined
quality of these deep sleep
brainwaves at night that acts
like a file transfer mechanism.
It takes memories from
a short-term, vulnerable
reservoir and shifts
them to a more permanent,
long-term storage
site within the brain
called the cortex, this big,
wrinkled, massive tissue
that sits atop of your brain.
And it means that when you
wake up the next morning,
there are two benefits.
First, having shifted
memories of yesterday
to that long-term, safe
storage haven in the brain,
they are protected
so that you will
remember rather than forget.
The second benefit, however, is
that having shifted those files
from that short-term reservoir,
almost like moving files
from a USB stick,
you've cleared out
all of that
memory-encoding capacity,
so that when you
wake up the next day,
you can start acquiring
new files all over again.
You can start learning anew.
So it's this elegant, beautiful,
symbiotic system of memory that
happens each and every night.
And it's important
that we understand
what, during sleep, actually
transacts these memory
benefits, because there are
real medical and societal
implications.
And let me just tell
you about two areas
that we've moved
this work out into.
I'll begin clinically and
specifically the context
of aging and dementia.
Because I think many
of us have a sense
or even know that
as we get older,
our learning and memory
abilities start to fade.
They begin to decline.
But what we've also
known for many decades
is that a physiological
signature of aging
is that your sleep gets worse.
And not just any type of sleep--
especially that deep
quality of sleep
that I was just describing.
And only last year, we
finally published evidence
that these two factors are
not simply co-occurring.
They are significantly
interrelated.
And it suggests that the
disruption of deep sleep
is perhaps an underappreciated
factor that is contributing
to what we call cognitive
decline, or memory decline,
in aging, and most
recently, we've
discovered, in Alzheimer's
disease as well.
Now, I know this is
remarkably depressing news.
I understand.
It's in the mail.
It's coming at you.
But there is a potential
silver lining here,
because unlike many of the
other factors that we know
are associated with
aging and dementia--
for example, changes in
the physical structure
of the brain or even changes in
the vasculature of the brain--
those are fiendishly
difficult to treat right now.
And we don't have any
good wholesale approaches
in medicine.
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.
And one way that
we are approaching
this at my Sleep Center is
not by using sleeping pills,
by the way.
They are blunt
instruments that do not
produce naturalistic
sleep, and they've
been associated with a higher
risk of death and cancer.
And I'm happy to speak about
that evidence during the Q&A,
and it's discussed
in the book as well.
What we are actually doing
is developing a method
based on this technology.
It's called direct-current
brain stimulation.
It sounds like the stuff
of science fiction.
It's actually science fact.
You apply electro
pads to the head,
and you insert a small amount
of voltage into the brain,
so small that you
tend not to feel it.
But it has a measurable
impact on physiology.
Now, if you apply this
stimulation during sleep,
in young, healthy
adults, as if you're
sort of singing in time with
those deep sleep brain waves,
not only can you
actually amplify
the size of those deep sleep
brain waves, but in doing so,
you can almost double the
amount of memory benefit
that you get from sleep.
The question now is
whether we can translate
this same affordable,
potentially portable technology
into older adults and
those with dementia.
Can we restore back some
healthy quality of deep sleep?
And in doing so, can we salvage
aspects of learning and memory
function?
That is my real hope now.
That's one of our moonshot
goals, as it were.
I should note, by the
way, because I always
get asked this question--
people will say, where can I
buy one of those devices?
I want one yesterday and
I want five more tomorrow.
And they are not yet
FDA-approved for use in sleep.
You can buy them
on the internet.
I strongly advise against that.
Just read around,
some horror stories.
People have misaligned
the voltage, skin burns,
they've lost their
eyesight for several days.
Hang on.
We are desperately
trying to bring this
to fruition as soon as we can.
So that's sleep and memory
in a clinical context.
But let me speak
about sleep and memory
in society and specifically
here within education.
Because if sleep really is
so important for learning
and memory, then enhancing
sleep in a context where,
arguably, it matters most
should prove transformative.
And it has because there
are several counties
throughout the
United States that
have started to delay
their school start times
and then measure the
academic consequence.
Now, one of the earliest
test case examples
happened in Edina in Minnesota.
It's a township that sits
just outside of Minneapolis.
And they shifted their
school start times from 7:25
in the morning to
8:30 in the morning.
By the way, what
are we doing trying
to educate our next generation
at 7:25 in the morning?
[LAUGHTER]
To give you a sense of this,
buses for a 7:25 start time
will often begin leaving
at 5:30 in the morning.
That means that
some kids are having
to wake up at 5:15, 5
o'clock, maybe even earlier.
This is lunacy.
But in Edina, it was the
beginnings of a movement.
And the metric that they used to
assess the academic consequence
was this--
SAT scores.
And they focused their analysis
on the top 10% performing
students, arguably those
that have the least
to gain in terms of any further
improvement by way of sleep.
Now, in the year before
they made the time change,
that top 10% performing
students got an average score
of 1,288, which is a
very respectable score.
The following year
when students were now
going to school at
8:30 in the morning,
the average SAT score was--
AUDIENCE: Whoa.
AUDIENCE: [WHISTLES]
MATTHEW WALKER: --1,500.
That is a 212-point increase,
which is non-trivial.
That will change which tier of
university those school kids
end up going to and
perhaps, as a consequence,
their subsequent
life trajectories.
Now, some people have questioned
aspects of the Edina study,
and I think for
perhaps good reason.
But in all of the subsequent
carefully controlled studies,
the data is
unequivocal, I think.
Academic grades increase,
behavioral problems decrease,
truancy rates decrease, and
psychological and psychiatric
issues also decrease.
But something else actually
happened in this story
of later school start times.
And it was something that
we did not anticipate.
The life expectancy of
students actually increased.
And you think, I
don't understand.
How does that work?
Does anybody know
what the leading cause
of death in late-stage teenagers
is throughout most developed
nations?
AUDIENCE: Suicide.
MATTHEW WALKER: Suicide
is actually second.
It's car crashes.
And here sleep
matters enormously.
Another example comes from
Teton County in Wyoming.
They shifted their
school starts from 7:35
in the morning to
8:55 in the morning.
And then they measured the
reduction in car crashes
in this narrow age
of just 16 to 18.
The only thing perhaps more
remarkable than the extra hour
of sleep that those
students reported getting
was the drop in
vehicle accidents.
There was a 70% reduction.
Just to sort of frame
that in context,
the advent of ABS technology,
what we call anti-lock braking
systems that prevent your
wheels from locking up
into hard braking, so that
you can still safely maneuver
a vehicle, that dropped
accident rates by 20% to 25%.
And some deemed it
to be a revolution.
But here is a
biological factor--
sleep that will drop
accident rates by up to 70%.
I think it's time for us to
reconsider the importance
of sleep in education.
When sleep is abundant,
minds flourish.
And if our goal
as educators truly
is to educate and not
risk lives in the process,
then I fear that we may
be failing our children
in a significant manner
with this incessant model
of early school start times.
So that's sleep for learning,
memory, aging, Alzheimer's.
What else is sleep good for?
Let me tell you that sleep is
essential to help stabilize
your emotional
and mental health.
And without sleep, the
emotional circuits of your brain
become hyperactive
and irrational.
Allow me to demonstrate with
a sleep-deprived subject,
because it turns out
that we do video diaries
with our participants throughout
the deprivation night.
And you go to meet one
under the pseudonym of Jeff.
It's 11:30 at night.
Jeff has been awake
for about 16 hours.
And I'm actually just going
to plug in the audio here
to see if I can get you
some audio playing out.
Jeff's just entered the study.
He's been awake for
a normal 16 hours.
And perhaps let's
hear from Jeff what
his sort of hopes
and aspirations
are for the deprivation period.
[VIDEO PLAYBACK]
- Hey.
It's about 11:27 right now.
I've been here for about an--
I think about an hour now.
Yeah, about an hour.
So it's the first hour.
I'm writing my paper right
now, a 30-page paper.
Hopefully I can get some of it
done before I get too sleepy.
[PLAYBACK ENDS]
MATTHEW WALKER: So that's Jeff.
Perfectly likable,
affable chap who's
hoping to get his 30-page
report complete in a night
of sleep deprivation.
[LAUGHTER]
Classic delusional
under-graduate thinking,
I have to say.
I see it all of the
time in my students.
So now let's
fast-forward the clock.
It's now 5:30 the
following morning.
Jeff has now been awake
for 22 hours straight.
And instantly, you'll notice
one of the hallmark features
of sleep deprivation, which is
that you actually slide down
in your chair.
You can look around the room
right now, actually, and see.
Jeff's down about
six or seven inches.
It's about an inch
for every hour
that you've been awake
beyond the standard 16
based on our highly
sophisticated machine-learning
algorithms.
But in all seriousness, notice
how emotionally different Jeff
has become.
Some people have, I
think perhaps unkindly,
described him as becoming
a little bit emotionally
unhinged.
So let's hear how that
30-page report has been going.
And I do apologize ahead
of time for the profanity.
[LAUGHTER]
[VIDEO PLAYBACK]
- Hello.
I'm very angry
right now, because I
didn't get any fucking--
could I curse on this?
Are they going to, like--
whatever.
[LAUGHS]
They probably think I'm
crazy after all this.
I'm very lucid, actually.
[END PLAYBACK]
[LAUGHTER]
MATTHEW WALKER:
So did you notice
how Jeff went from
being remarkably
upset and annoyed
that he got none
of his 30-page report
complete to then finding
it almost hilarious?
He was nearly sort
of punch-drunk giddy
on sleep deprivation and
then came right back down
to baseline again.
That is a remarkably
abnormal emotional distance
to travel within such
a short time period.
And I think it emphasizes the
type of destabilizing influence
that a lack of sleep has
on our emotional integrity.
And we've since discovered
what actually changes
within your brain to produce
this type of pendulum,
emotional irrationality.
There's a structure very
deep within your brain called
the amygdala.
And you can see it here
in these red colors.
Again, you have one on the
left side and one on the right.
And the amygdala is one
of the centerpiece regions
for the generation of
strong, emotional reactions,
including negative reactions.
And when we looked
at this structure
in those people who'd had a full
night of sleep, here in green,
we saw a nice, controlled,
modest degree of reactivity.
Yet in those people who
were sleep deprived,
we saw this amplified,
almost aggravated degree
of reactivity.
The amygdala was actually
60% more responsive
under conditions
of a lack of sleep.
And it's almost as
though, without sleep, we
become all sort of
emotional gas pedal
and too little sort of
regulatory-control brake.
But what is perhaps
more concerning,
however, is that this represents
a neurological signature that
is not dissimilar to numerous
psychiatric conditions.
And we're now finding
significant links between sleep
disruption and conditions
such as depression;
anxiety, including PTSD;
schizophrenia; and tragically,
suicide as well.
In fact, we cannot find a single
psychiatric condition in which
sleep is normal.
I think sleep has
a profound story
to tell in our understanding,
in our treatment,
and perhaps even may contribute
to our ultimate prevention
of grave mental illness.
So that's sleep for the
brain, but sleep is just
as essential for your body.
And here I could have gone into
any one of the model systems
and spoken about it in detail.
We've already
spoken a little bit
about sleep loss and
the reproductive system.
I could tell you about sleep
loss and the metabolic system,
that after one week
of short sleep,
your blood sugar
levels are disrupted
so significantly that your
doctor would classify you
as being pre-diabetic.
Or I could tell you
about sleep loss
and the cardiovascular system,
that all it takes is one hour.
Because there is a
global experiment
that is performed on 1.6 billion
people across 70 countries
twice a year, and it's
called daylight savings time.
Now, in the spring, when
we lose one hour of sleep,
we see a subsequent 24%
increase in heart attacks.
In the fall, when we
gain an hour of sleep,
we see a 21% decrease
in heart attacks.
That is how fragile your body
is to even just the smallest
perturbations of sleep.
I think many of us perhaps
don't think anything
of losing an hour of sleep.
But as a deep dive,
I actually want
to focus on this-- sleep
and the immune system.
And here I'll introduce these
delightful blue elements
in the image.
They are called
natural killer cells.
Think of natural killer
cells like the Secret Service
agents of your immune system.
They are very good
at identifying
dangerous foreign elements
and eliminating them.
In fact, what they're
doing here in this image
is embedding themselves into
a malignant, a cancerous tumor
mass, and destroying it.
And many of you may not
know, but today your body
produced cancer cells.
And it's always doing this.
What stops those cancer cells
from becoming the disease
that we call cancer is, in part,
these natural killer cells.
So what you want is a virile
set of these immune assassins
at all times.
And sadly, that's exactly
what you don't have
if you're not sleeping enough.
So here in this study from my
wonderful colleague Mike Irwin,
you're not going to
have your sleep deprived
for an entire night.
You're simply going to have
your sleep restricted to four
hours for one single night.
And then we're
going to look to see
what is the percent reduction
in immune cell activity
that you suffer.
And it's not small.
It's not 10%, it's not 30%.
There was a 70% drop in
natural killer cell activity.
That's quite a concerning
state of immune deficiency.
And it happens quickly,
essentially after just one
bad night.
Imagine the state of
your immune system
after weeks, if not months,
of insufficient sleep.
And it perhaps should
then come as no surprise
to learn that we now
have significant links
between short sleep and
numerous forms of cancer.
Currently that list includes
cancer of the bowel,
cancer of the prostate,
and cancer of the breast.
In fact, the link between
a lack of sleep and cancer
is now so strong that recently
the World Health Organization
decided to classify any
form of nighttime shift work
as a probable carcinogen.
In other words,
jobs that may induce
cancer because of a disruption
of your sleep-wake rhythms.
So you may have heard
of that old maxim--
oh, you can sleep
when you're dead.
Well, I'm being
absolutely serious.
It is mortally unwise advice.
Because if you adopt that
mindset, we know from the data
that you will now
live a shorter life
and the quality of
that shorter life
will be significantly worse.
Epidemiological
studies teaches this.
Short sleep predicts
a shorter life.
It predicts all-cause mortality.
And the bad news, I'm
sorry, keeps coming.
Because if you are fighting
a battle against cancer
and not getting
sufficient sleep,
that cancer may grow more
quickly and aggressively.
So here I actually
want to feature work
not from my own sleep center,
but by a scientist called
David Gozal who works at
the University of Chicago.
And he examines the relationship
between sleep loss and cancer
in mice.
Now, I know this
isn't for everyone,
so I will tell you when
to look away if you'd
prefer not to see this.
But in one of the
studies that he did,
he inoculated some mice with
cancer cells on their back.
And then he gave that cancer
a one-month period to grow.
And at the end of that one
month, he resected the skin
and measured the size
of that tumor mass.
Half of the mice were
allowed to sleep normally
during that one-month period.
The other half had
their sleep disrupted.
Not total deprivation.
They just sort of played
with them a little bit more
during the day and during the
night to restrict their sleep.
So in a second, I'm going
to play a video with David
illustrating the results.
Now would be the
time to look away
if you would prefer to do so.
And here you can
see him pointing
to a mouse on a monitor
with the skin resected,
and you can clearly see
that tumor mass there.
This is in one of the mice that
was allowed to sleep normally
during that one month.
I'll play the video, and he will
reveal behind it another mouse.
That mouse was in the
sleep restriction group,
and you will see the
difference in the tumor mass.
This is the difference.
There was a 200%
increase in the speed
and the size of that
cancerous growth linked
to insufficient sleep.
Worse still, the cancer
in those under-slept mice
had actually metastasized.
That's just a
medical description
meaning that it had
breached the original origin
and started to
invade other areas--
bone, other organs,
as well as brain.
When cancer becomes
metastatic, that's
when we see mortality
rates escalate.
So if you are fighting
a battle against cancer
and not getting
sufficient sleep,
it may be the equivalent
of placing gasoline
on an already aggressive fire.
Sleep loss is an accelerant.
And we now know that it produces
a harmful biological fertilizer
for the more rapid and
rampant growth of cancer.
Now, if increasing your risk
of developing Alzheimer's
or cancer by way
of a lack of sleep
were not sufficiently
disquieting,
we have since discovered
that a lack of sleep
will even erode the very
fabric of biological life
itself, your DNA genetic code.
So here in this study, they
took a group of healthy adults
and limited them to six
hours of sleep for one week.
And then they
measured the change
in the gene activity
profile compared
to when those same
individuals were getting eight
hours of sleep for a week.
And there were two
critical results here.
First, a sizable and
significant 711 genes
were distorted in terms
of their activity,
caused by six hours of sleep.
And that's relevant, by the way.
We know that almost one out
of every two American adults
are trying to survive on
six hours of sleep or less
during the week.
The second result was that
about half of those genes
were actually increased
in their activity.
The other half were actually
decreased in their activity.
Those genes that were
decreased by a lack of sleep
were genes related to numerous
aspects of the immune system,
which fits very well with
the evidence I was just
discussing regarding cancer.
Those genes that were actually
increased in their activity
or what we call up-regulated
in their expression
were genes related to
the promotion of tumors,
genes that were related
to chronic inflammation
within the body,
and also genes that
were related to stress
and, as a consequence,
cardiovascular disease.
Now, I think many
individuals in society
feel uncomfortable about
the idea of genetically
modified embryos or even
genetically modified food.
But by choosing to get
insufficient sleep,
we may be forced
to accept that we
are performing a similar
genetic modifying
experiment on ourselves.
And if we don't let our
children get the sleep that they
so desperately
need, then we may be
inflicting a similar genetic
engineering experiment on them
as well.
There is simply no
aspect of your physiology
that seems to be able to
retreat at the sign of sleep
deprivation and
get away unscathed.
It's almost like a broken
water pipe in your home.
Sleep loss will leak down
into every nook and cranny
of your biology, even
tampering with the very
DNA nucleic alphabet that
spells out your daily health
narrative.
So where does this leave us?
What is the piece of
sort of mental furniture
I would like to gift to
you as we finish the talk?
Well, it would be this.
Sleep is not an optional
lifestyle luxury.
Sleep is a non-negotiable
biological necessity.
It's a life support system.
And it is mother nature's best
effort yet at contra-death.
And the decimation of sleep
throughout industrialized
nations is having a
catastrophic impact
on our health, our
wellness, and the safety
and the education
of our children.
It's a silent sleep
loss epidemic,
and it is fast becoming one
of the greatest public health
challenges that we now
face in the 21st century.
I believe it is now time
for us to reclaim our right
to a full night of sleep,
and without embarrassment
and without that terrible
stigma of laziness.
And in doing so, we
may finally remember
what it feels like to
be awake during the day.
And with that soapbox rant over,
I will simply say good night,
good luck, and above all,
I do hope you sleep well.
Thank you very much indeed.
[APPLAUSE]
I think we've got lots of
times for questions, I think.
AUDIENCE: I don't know
if you can hear me,
but thank you so
much for the talk.
It was actually
very informative.
I have two questions for you.
Number one, I have
a five-year-old
and then there's myself, right?
So how much sleep
should we be getting?
And number two, is there any
disadvantage of oversleeping?
So let's say if I sleep 10
hour, 15 hours in a day--
MATTHEW WALKER: Yeah.
AUDIENCE: Is there any
disadvantage to that?
MATTHEW WALKER:
So great question.
So firstly, recommendations
for sleep, you
can find them on the
National Sleep Foundation
website for all ages.
For the average adult,
the recommendation,
World Health
Organization-- eight hours;
range, seven to nine.
Once the average
human being gets
below seven hours
of sleep, we can
measure objective impairments.
So people who say, I can survive
on six hours of sleep, there's
a problem with
that, which is this.
Your subjective
sense of how well
you think you're doing
without sufficient sleep
is a miserable
predictor of objectively
how you're doing without
sufficient sleep.
So it's probably a little bit
like a drunk driver at a bar.
They've had seven shots,
they pick up their car keys,
and they say, I'm fine to drive.
And your response is,
no, I know that you
think you're fine to drive, but
trust me, objectively, you're
not.
The same is true
for a lack of sleep.
Your second question
is fascinating.
Can I sleep too much?
Well, there are anecdotes
of something called a sleep
hangover, where you
sort of oversleep
and then you feel worse almost.
When you oversleep,
it usually means
that you're trying to sleep
off a debt that you've
lumbered yourself with.
So if you could sleep past your
alarm, if it didn't go off,
then you're under-slept, because
it's physiologically impossible
to sleep too much
if you're healthy.
Now, there is one
piece of evidence
that suggests something called
hyper-somnia, excessive sleep.
That principally expresses
itself in depression.
But if you look at that data,
it's actually very difficult
to tell.
Is it people just reporting
being in bed for longer
rather than sleeping longer?
So I think it's
unclear right now.
But let me just take it
to a theoretical realm.
Could there be such a
thing as too much sleep?
I think yes.
But don't forget.
The same is true for the
other three essential factors
of life-- oxygen,
food, and water.
Can you eat too much?
Yes.
Can you overhydrate?
Yes.
Can you increase blood pressure,
cause stroke and heart attack
by excessive water intake?
It happened in the 1990s
with the ecstasy craze,
where people were dehydrating.
Governments told
them, drink lots.
They drank too much.
Cardiac events.
Can you actually become
hyper-oxygenated?
So you get free radical
species, dangerous for cells.
Yes, you can.
Is there such a thing
as too much sleep?
We haven't found it yet,
but I suspect probably so.
It's a bell-shaped curve.
It's a U-shaped function in
terms of benefit, not linear.
But on most people in danger
of getting too much sleep,
au contraire.
AUDIENCE: Thank you
for the great talk.
MATTHEW WALKER: Thank you.
AUDIENCE: Do you also
have any information
on how quickly people
recover after they switch
from kind of short sleep periods
to kind of more normal sleep
periods?
Because you only mentioned
kind of as a-- one evidence was
the DST change, or when we sleep
one hour more, kind of things
get better in terms
of cardiac problems.
But is it quick, the
recovery as well?
As quick as the downhill
movement [INAUDIBLE]??
MATTHEW WALKER: Yeah.
It's a great question.
So different aspects of
your brain and your body
seem to come back online
to a status of health
with recovery sleep.
And those temporal
profiles are different
based on-- even within the
immune system, for example,
some components take longer to
come back online than others.
What I would note, however,
is that you can never
get back all that you've lost.
This is another one of
those myths with sleep.
So sleep is not like the bank.
You cannot accumulate a debt
and then pay it off at a later
point in time, which is what
most of modern society does.
Chronic short sleep
during the week,
then you binge at the weekend.
It's what I call sleep bulimia.
It's what is otherwise
known as social jet lag.
Now, if I were to take you and
deprive you of sleep for one
single night, eight
hours of lost sleep,
and then I give you
all of the sleep
that you want for
however many nights
and we keep recording
you, your brain
never recovers all of
that lost eight hours.
It will try to get
back some of it.
It will never get
back all of it.
Why is that the
case, we can ask?
Why doesn't your brain have
a credit system for sleep?
Because there's precedent
for this in biology.
You have one for energy.
It's called a fat cell.
You can actually store
up credit calorically
and spend it when
you go into famine.
Now, most of us aren't
in that danger anymore.
But during evolution,
we faced that challenge,
so we came up with a solution
called the adipose cell.
Where is the fat cell for sleep?
Why isn't it there?
The reason is this.
Human beings are
the only species
that deliberately deprive
themselves of sleep
for no apparent reason.
[LAUGHTER]
What that means is that
mother nature has never
had to face the challenge
through evolution
of coming up with a safety net
because of insufficient sleep.
So there is no
mechanism of safety.
There is no credit system.
AUDIENCE: So similar to how
you can take supplements
after exercising, have you done
any research about supplements
that can help sleeping--
well, without the device yet?
And as a side note,
what about melatonin?
MATTHEW WALKER: So no
drugs or supplements
that we have currently
produce naturalistic sleep.
Chemically, it's an
incredibly complex job.
Now, I don't want to dismiss
people at drug companies.
I'm not against medication.
I'm not anti all medication.
If medications work,
I'm all for them.
It's just that all
of the sleeping
medications that we
have right now don't
produce naturalistic sleep.
Most of them are a
class of drugs that we
call the sedative hypnotics.
Sedation is not sleep.
All you're doing is
knocking the cortex out.
You're not producing
naturalistic sleep.
And as I said and I
mentioned in the book,
they are also linked to
a higher risk of death--
and it's considerably higher--
as well as cancer.
What about melatonin?
Well, melatonin turns out not
to be an effective sleep aid.
And it shouldn't surprise us
based on how melatonin works.
Melatonin helps time
the onset of sleep,
but it doesn't help in the
creation of sleep itself.
So the analogy would
be melatonin is
like the starting official
in the 100-meter race
at the Olympics.
Melatonin gathers all of the
racers to the starting line
and begins the race, but
that official themselves
does not participate in the
great sleep race itself.
That's a whole different set of
brain mechanisms and chemicals.
That's why melatonin
is not efficacious
once you're stable
in a new time zone.
Now, I will say this, however.
If you're taking melatonin
and you feel it's beneficial,
keep taking it, because
the placebo effect
is one of the most reliable
effects in all of pharmacology.
I mean, that tells you
something, by the way,
something profound.
There is such a thing
as mind over matter.
And there is now a wonderful
science of the placebo effect.
It's very real.
And we dismissed
it for a long time.
I hope that answers
both your questions.
AUDIENCE: Thank you.
MATTHEW WALKER: Sure.
AUDIENCE: I was wondering--
again, thank you for the talk.
MATTHEW WALKER: Sure.
AUDIENCE: Does the time period
between when you wake up
to when you start using
your brain for learning
or whatever, also
play a difference?
If a person had a full
eight hours of sleep
but they don't go to
school until evening
when they have evening school,
do they learn worse than
if they could have went
to a morning school
and started learning
in the morning?
MATTHEW WALKER: So it's a
very interesting question.
When on the clock face
is learning, let's
say, most sort of beneficial?
Well, once you're waking
at a reasonable time,
it seems as though there
is some degree of stability
of learning across the day.
However, there does seem to
be a gradual deterioration.
And we've done some
of these studies
to basically map the
time course, sort
of the Great Depression of
learning across the day.
And we've inserted naps, and we
can actually restore learning.
But I would like
to come on to naps.
Someone should
ask me about that,
because they're a double-edged
sword with danger.
But what we do know from
those school studies
where they delayed the
school start times, where
you get the greatest
grade-point increases is not
in all classes across the
day, but it's especially
in those first morning classes.
But I think that that's
less about your brain
being better at
learning in the morning
than it was about when you
were starting so early,
it was just so detrimental
to try and learn.
So sort of you'd
lowered the floor
rather than raise the ceiling.
So yep.
But to me, it makes
sense that learning
is somewhat stable
across 16 hours,
because if you were to design
a system of memory that
could only learn in the last
couple of hours of wakefulness,
then why are we awake
for the other 14?
And we seem to have a system
of memory that gives us
a capacity for about 16
hours of recording in humans
before sleep is required.
AUDIENCE: A quick
followup question.
Do you do any study on
other brain activities
like coding-- well, not coding,
but more advanced [INAUDIBLE]..
I try not to schedule
morning meetings,
because everybody is asleep
and nobody's making decisions.
MATTHEW WALKER: Yes.
So we've done lots of studies on
all aspects of brain cognition.
We've done decision-making,
judgment making.
We've done creativity,
emotional regulation.
We've done visual
attention aspects.
We've done motor skill learning.
And it follows the same
profile, which is essentially
when sleep is in high
volumes, all of those things
are supported.
Different operations
within the brain
rely on different
stages of sleep
at different times
of night, however.
It's not just one
stage of sleep that
does it all for all of your
brain sort of mechanisms
and apparatus features.
And this is why there is no
single one stage of sleep
that's important.
People will say, oh, how
can I get more REM sleep?
And I would say, why do
you want more REM sleep?
Or how can I get
more deep sleep?
Mother nature took
about 3.6 million years
to figure that out.
Just let her do her job.
She'll see you well.
AUDIENCE: Quick
question, basically.
How do drugs, any kind of
drugs-- medicine, alcohol,
marijuana-- how
would it basically
affect the brain activity during
the night, during the sleep?
MATTHEW WALKER: So how do
drugs, perhaps some legal,
some non-legal, impact sleep?
I'll focus on
marijuana and alcohol
since you mentioned them.
Alcohol is perhaps the
most misunderstood drug
when it comes to sleep.
People say, you have a nightcap,
and I fall asleep better.
Untrue.
Alcohol is also a class of drugs
that we call the sedatives.
And once again, that's
not natural sleep.
What you're doing is simply
removing consciousness
by way of alcohol.
You're not putting yourself
into natural sleep.
Two more problems with alcohol.
First, it will
fragment your sleep
with awakenings
throughout the night.
The problem is that they
are so brief that you
tend not to remember them
and commit them to memory.
So you wake up the next
morning feeling unrefreshed,
but you don't understand why--
that it was the alcohol
fragmenting your sleep.
Finally, alcohol is very
effective at blocking your REM
sleep, at blocking
your dream sleep.
So alcohol-- misunderstood,
should be avoided.
Marijuana-- people
use it to try and help
them get to sleep or relax.
The problem is marijuana
also seems to fragment sleep.
It also seems to block
rapid-eye movement sleep.
Probably the other chemical
that deserves mention
here is caffeine.
Caffeine, most people
know, is an alerting drug.
It's actually a class
of drugs that we call
the psychoactive stimulants.
It's the only legal stimulant
that we readily give
to our children, by the way.
Caffeine can obviously
keep you awake at night.
But some people
will say, I'm one
of those who can have a cup of
coffee, and I fall asleep fine.
The problem there is that
even if you fall asleep,
the depth of the deep
sleep that you have
is not as deep as
if you were to have
sleep that didn't have
caffeine swilling around
within the brain.
So again, you wake up the next
morning feeling unrefreshed.
You don't remember waking up
or struggling to fall asleep,
so you don't think
it's the caffeine.
But now you need
two cups of coffee
rather than one
the next morning.
You build up this vicious
cycle, and it's probably
the reason that caffeine is the
second most traded commodity
on the surface of
the planet after oil.
I don't think there's probably
any other statistic that
bares out how sleep
deprived we are
throughout
industrialized nations.
AUDIENCE: Cool.
Thank you.
One more quick question.
How much of the sleep every
night is basically enough?
It's eight hours maybe?
MATTHEW WALKER: As
I said, once you
get below seven hours
of sleep, that's
when we can measure
objective impairments.
Yup.
AUDIENCE: Thank you.
MATTHEW WALKER: But
that's once we can
measure objective impairments.
It doesn't mean that if we
had more sensitive tools,
we would measure it at
seven hours and 15 minutes.
AUDIENCE: I wondered
about blue light exposure,
especially from devices.
And back a couple
years ago, I got
the blue light-blocking glasses.
And it does seem to actually
give better sleep at night.
I was curious what the
research is behind that.
MATTHEW WALKER: Yeah, that
one is actually not a placebo
effect, it turns out.
So the studies are
very clear right now.
As an industrialized
set of nations,
we are a dark, deprived society.
And we need darkness
because the way
that darkness works
is that it actually
removes the breaks from
the hormone melatonin
that I described
that needs to rise
to help time the normal
onset of healthy sleep.
So if you're bathed in
electrical light at night,
even though it's not as
powerful as daylight,
it can keep the brake
pedal on melatonin.
Now, they did some
fascinating studies
where you read on
an iPad for one
hour versus just reading a
normal book with dim light.
And firstly, relative to
that one hour of dim light,
normal book reading, the
one hour of iPad reading
firstly delayed that
spike in melatonin
by two to three hours.
So here, if you're reading
the iPad in Seattle,
we're almost all
the way to Hawaii
in terms of our biological
melatonin rhythms.
That's how shifted
and delayed we are.
Second, the sleep
was not as good.
REM sleep was disrupted,
and people subjectively felt
worse and less refreshed
the next morning.
And it took a few
days before it washed
itself away after they ceased.
So I think the
recommendation right now
is try to limit screen
time in the last hour.
I know where I'm speaking
right now, which is at Google,
and what that means.
You can install software
that helps desaturate
the most harmful wavelength of
light, which is the blue light.
You can also put
those spectacles on.
They seem to work as well.
But overall, try to
decrease stimulation.
Blackout curtains also great at
night during the night in bed.
AUDIENCE: Yeah, a followup
on the blackout curtains.
One of the things
I've found is it's
really hard to get
up in the morning
if the room is all blacked out.
Having that natural light
come in is important.
And I wondered too--
which is worse, to have
any of this light coming
in during the
nighttime versus having
to deal with an
unnatural alarm clock
waking you up in the morning?
MATTHEW WALKER: Yeah.
I mean, it sounds as though
what you're experiencing
is sort of what we call
a sleep inertia, which
is when you wake up.
It usually means
that you're sort
of waking up at a
time that's slightly
offset from your natural
biological tendency.
With that, you can use daylight
to perhaps try and help you.
Some people actually
use eye masks
in the first part of the night.
And at some point, they
will take the eye mask off
and then help with the
exposure to the daylight,
because they've
kept their curtains
non-blackout in that regard.
But that's a tricky
one to balance.
Yeah.
JOSH: I know there are
a lot more questions.
It's coming up on 2 o'clock,
so we're going to cut it off.
But Dr. Walker will stay,
and he's going to sign books.
We're selling a
few of the copies.
And so just everybody, let's
give Dr. Walker our hands.
MATTHEW WALKER: Thank
you very much indeed.
[APPLAUSE]
Thank you.
Thank you so much.
Thank you.
