https://www.theguardian.com/lifeandstyle/2017/sep/24/why-lack-of-sleep-health-worst-enemy-matthew-walker-why-we-sleep
The shorter your sleep, the shorter your life: the new sleep science
Leading neuroscientist Matthew Walker on why sleep deprivation is
increasing our risk of cancer, heart attack and Alzheimer’s – and what
you can do about it
Rachel Cooke
Sunday 24 September 2017 08.00 BST
Matthew Walker has learned to dread the question “What do you do?” At
parties, it signals the end of his evening; thereafter, his new
acquaintance will inevitably cling to him like ivy. On an aeroplane, it
usually means that while everyone else watches movies or reads a
thriller, he will find himself running an hours-long salon for the
benefit of passengers and crew alike. “I’ve begun to lie,” he says.
“Seriously. I just tell people I’m a dolphin trainer. It’s better for
everyone.”
Walker is a sleep scientist. To be specific, he is the director of the
Center for Human Sleep Science at the University of California,
Berkeley, a research institute whose goal – possibly unachievable – is
to understand everything about sleep’s impact on us, from birth to
death, in sickness and health. No wonder, then, that people long for his
counsel. As the line between work and leisure grows ever more blurred,
rare is the person who doesn’t worry about their sleep. But even as we
contemplate the shadows beneath our eyes, most of us don’t know the half
of it – and perhaps this is the real reason he has stopped telling
strangers how he makes his living. When Walker talks about sleep he
can’t, in all conscience, limit himself to whispering comforting
nothings about camomile tea and warm baths. It’s his conviction that we
are in the midst of a “catastrophic sleep-loss epidemic”, the
consequences of which are far graver than any of us could imagine. This
situation, he believes, is only likely to change if government gets
involved.
Walker has spent the last four and a half years writing Why We Sleep, a
complex but urgent book that examines the effects of this epidemic close
up, the idea being that once people know of the powerful links between
sleep loss and, among other things, Alzheimer’s disease, cancer,
diabetes, obesity and poor mental health, they will try harder to get
the recommended eight hours a night (sleep deprivation, amazing as this
may sound to Donald Trump types, constitutes anything less than seven
hours). But, in the end, the individual can achieve only so much. Walker
wants major institutions and law-makers to take up his ideas, too. “No
aspect of our biology is left unscathed by sleep deprivation,” he says.
“It sinks down into every possible nook and cranny. And yet no one is
doing anything about it. Things have to change: in the workplace and our
communities, our homes and families. But when did you ever see an NHS
poster urging sleep on people? When did a doctor prescribe, not sleeping
pills, but sleep itself? It needs to be prioritised, even incentivised.
Sleep loss costs the UK economy over £30bn a year in lost revenue, or 2%
of GDP. I could double the NHS budget if only they would institute
policies to mandate or powerfully encourage sleep.”
I get on a flight at 10am when people should be at peak alert, and
half of the plane has immediately fallen asleep
Why, exactly, are we so sleep-deprived? What has happened over the
course of the last 75 years? In 1942, less than 8% of the population was
trying to survive on six hours or less sleep a night; in 2017, almost
one in two people is. The reasons are seemingly obvious. “First, we
electrified the night,” Walker says. “Light is a profound degrader of
our sleep. Second, there is the issue of work: not only the porous
borders between when you start and finish, but longer commuter times,
too. No one wants to give up time with their family or entertainment, so
they give up sleep instead. And anxiety plays a part. We’re a lonelier,
more depressed society. Alcohol and caffeine are more widely available.
All these are the enemies of sleep.”
But Walker believes, too, that in the developed world sleep is strongly
associated with weakness, even shame. “We have stigmatised sleep with
the label of laziness. We want to seem busy, and one way we express that
is by proclaiming how little sleep we’re getting. It’s a badge of
honour. When I give lectures, people will wait behind until there is no
one around and then tell me quietly: ‘I seem to be one of those people
who need eight or nine hours’ sleep.’ It’s embarrassing to say it in
public. They would rather wait 45 minutes for the confessional. They’re
convinced that they’re abnormal, and why wouldn’t they be? We chastise
people for sleeping what are, after all, only sufficient amounts. We
think of them as slothful. No one would look at an infant baby asleep,
and say ‘What a lazy baby!’ We know sleeping is non-negotiable for a
baby. But that notion is quickly abandoned [as we grow up]. Humans are
the only species that deliberately deprive themselves of sleep for no
apparent reason.” In case you’re wondering, the number of people who can
survive on five hours of sleep or less without any impairment, expressed
as a percent of the population and rounded to a whole number, is zero.
The world of sleep science is still relatively small. But it is growing
exponentially, thanks both to demand (the multifarious and growing
pressures caused by the epidemic) and to new technology (such as
electrical and magnetic brain stimulators), which enables researchers to
have what Walker describes as “VIP access” to the sleeping brain.
Walker, who is 44 and was born in Liverpool, has been in the field for
more than 20 years, having published his first research paper at the age
of just 21. “I would love to tell you that I was fascinated by conscious
states from childhood,” he says. “But in truth, it was accidental.” He
started out studying for a medical degree in Nottingham. But having
discovered that doctoring wasn’t for him – he was more enthralled by
questions than by answers – he switched to neuroscience, and after
graduation, began a PhD in neurophysiology supported by the Medical
Research Council. It was while working on this that he stumbled into the
realm of sleep.
“I was looking at the brainwave patterns of people with different forms
of dementia, but I was failing miserably at finding any difference
between them,” he recalls now. One night, however, he read a scientific
paper that changed everything. It described which parts of the brain
were being attacked by these different types of dementia: “Some were
attacking parts of the brain that had to do with controlled sleep, while
other types left those sleep centres unaffected. I realised my mistake.
I had been measuring the brainwave activity of my patients while they
were awake, when I should have been doing so while they were asleep.”
Over the next six months, Walker taught himself how to set up a sleep
laboratory and, sure enough, the recordings he made in it subsequently
spoke loudly of a clear difference between patients. Sleep, it seemed,
could be a new early diagnostic litmus test for different subtypes of
dementia.
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After this, sleep became his obsession. “Only then did I ask: what is
this thing called sleep, and what does it do? I was always curious,
annoyingly so, but when I started to read about sleep, I would look up
and hours would have gone by. No one could answer the simple question:
why do we sleep? That seemed to me to be the greatest scientific
mystery. I was going to attack it, and I was going to do that in two
years. But I was naive. I didn’t realise that some of the greatest
scientific minds had been trying to do the same thing for their entire
careers. That was two decades ago, and I’m still cracking away.” After
gaining his doctorate, he moved to the US. Formerly a professor of
psychiatry at Harvard Medical School, he is now professor of
neuroscience and psychology at the University of California.
Does his obsession extend to the bedroom? Does he take his own advice
when it comes to sleep? “Yes. I give myself a non-negotiable eight-hour
sleep opportunity every night, and I keep very regular hours: if there
is one thing I tell people, it’s to go to bed and to wake up at the same
time every day, no matter what. I take my sleep incredibly seriously
because I have seen the evidence. Once you know that after just one
night of only four or five hours’ sleep, your natural killer cells – the
ones that attack the cancer cells that appear in your body every day –
drop by 70%, or that a lack of sleep is linked to cancer of the bowel,
prostate and breast, or even just that the World Health Organisation has
classed any form of night-time shift work as a probable carcinogen, how
could you do anything else?”
There is, however, a sting in the tale. Should his eyelids fail to
close, Walker admits that he can be a touch “Woody Allen-neurotic”.
When, for instance, he came to London over the summer, he found himself
jet-lagged and wide awake in his hotel room at two o’clock in the
morning. His problem then, as always in these situations, was that he
knew too much. His brain began to race. “I thought: my orexin isn’t
being turned off, the sensory gate of my thalamus is wedged open, my
dorsolateral prefrontal cortex won’t shut down, and my melatonin surge
won’t happen for another seven hours.” What did he do? In the end, it
seems, even world experts in sleep act just like the rest of us when
struck by the curse of insomnia. He turned on a light and read for a while.
Will Why We Sleep have the impact its author hopes? I’m not sure: the
science bits, it must be said, require some concentration. But what I
can tell you is that it had a powerful effect on me. After reading it, I
was absolutely determined to go to bed earlier – a regime to which I am
sticking determinedly. In a way, I was prepared for this. I first
encountered Walker some months ago, when he spoke at an event at
Somerset House in London, and he struck me then as both passionate and
convincing (our later interview takes place via Skype from the basement
of his “sleep centre”, a spot which, with its bedrooms off a long
corridor, apparently resembles the ward of a private hospital). But in
another way, it was unexpected. I am mostly immune to health advice.
Inside my head, there is always a voice that says “just enjoy life while
it lasts”.
The evidence Walker presents, however, is enough to send anyone early to
bed. It’s no kind of choice at all. Without sleep, there is low energy
and disease. With sleep, there is vitality and health. More than 20
large scale epidemiological studies all report the same clear
relationship: the shorter your sleep, the shorter your life. To take
just one example, adults aged 45 years or older who sleep less than six
hours a night are 200% more likely to have a heart attack or stroke in
their lifetime, as compared with those sleeping seven or eight hours a
night (part of the reason for this has to do with blood pressure: even
just one night of modest sleep reduction will speed the rate of a
person’s heart, hour upon hour, and significantly increase their blood
pressure).
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A lack of sleep also appears to hijack the body’s effective control of
blood sugar, the cells of the sleep-deprived appearing, in experiments,
to become less responsive to insulin, and thus to cause a prediabetic
state of hyperglycaemia. When your sleep becomes short, moreover, you
are susceptible to weight gain. Among the reasons for this are the fact
that inadequate sleep decreases levels of the satiety-signalling
hormone, leptin, and increases levels of the hunger-signalling hormone,
ghrelin. “I’m not going to say that the obesity crisis is caused by the
sleep-loss epidemic alone,” says Walker. “It’s not. However, processed
food and sedentary lifestyles do not adequately explain its rise.
Something is missing. It’s now clear that sleep is that third
ingredient.” Tiredness, of course, also affects motivation.
Sleep has a powerful effect on the immune system, which is why, when we
have flu, our first instinct is to go to bed: our body is trying to
sleep itself well. Reduce sleep even for a single night, and your
resilience is drastically reduced. If you are tired, you are more likely
to catch a cold. The well-rested also respond better to the flu vaccine.
As Walker has already said, more gravely, studies show that short sleep
can affect our cancer-fighting immune cells. A number of epidemiological
studies have reported that night-time shift work and the disruption to
circadian sleep and rhythms that it causes increase the odds of
developing cancers including breast, prostate, endometrium and colon.
Getting too little sleep across the adult lifespan will significantly
raise your risk of developing Alzheimer’s disease. The reasons for this
are difficult to summarise, but in essence it has to do with the amyloid
deposits (a toxin protein) that accumulate in the brains of those
suffering from the disease, killing the surrounding cells. During deep
sleep, such deposits are effectively cleaned from the brain. What occurs
in an Alzheimer’s patient is a kind of vicious circle. Without
sufficient sleep, these plaques build up, especially in the brain’s
deep-sleep-generating regions, attacking and degrading them. The loss of
deep sleep caused by this assault therefore lessens our ability to
remove them from the brain at night. More amyloid, less deep sleep; less
deep sleep, more amyloid, and so on. (In his book, Walker notes
“unscientifically” that he has always found it curious that Margaret
Thatcher and Ronald Reagan, both of whom were vocal about how little
sleep they needed, both went on to develop the disease; it is, moreover,
a myth that older adults need less sleep.) Away from dementia, sleep
aids our ability to make new memories, and restores our capacity for
learning.
And then there is sleep’s effect on mental health. When your mother told
you that everything would look better in the morning, she was wise.
Walker’s book includes a long section on dreams (which, says Walker,
contrary to Dr Freud, cannot be analysed). Here he details the various
ways in which the dream state connects to creativity. He also suggests
that dreaming is a soothing balm. If we sleep to remember (see above),
then we also sleep to forget. Deep sleep – the part when we begin to
dream – is a therapeutic state during which we cast off the emotional
charge of our experiences, making them easier to bear. Sleep, or a lack
of it, also affects our mood more generally. Brain scans carried out by
Walker revealed a 60% amplification in the reactivity of the amygdala –
a key spot for triggering anger and rage – in those who were
sleep-deprived. In children, sleeplessness has been linked to aggression
and bullying; in adolescents, to suicidal thoughts. Insufficient sleep
is also associated with relapse in addiction disorders. A prevailing
view in psychiatry is that mental disorders cause sleep disruption. But
Walker believes it is, in fact, a two-way street. Regulated sleep can
improve the health of, for instance, those with bipolar disorder.
I’ve mentioned deep sleep in this (too brief) summary several times.
What is it, exactly? We sleep in 90-minute cycles, and it’s only towards
the end of each one of these that we go into deep sleep. Each cycle
comprises two kinds of sleep. First, there is NREM sleep (non-rapid eye
movement sleep); this is then followed by REM (rapid eye movement)
sleep. When Walker talks about these cycles, which still have their
mysteries, his voice changes. He sounds bewitched, almost dazed.
“During NREM sleep, your brain goes into this incredible synchronised
pattern of rhythmic chanting,” he says. “There’s a remarkable unity
across the surface of the brain, like a deep, slow mantra. Researchers
were once fooled that this state was similar to a coma. But nothing
could be further from the truth. Vast amounts of memory processing is
going on. To produce these brainwaves, hundreds of thousands of cells
all sing together, and then go silent, and on and on. Meanwhile, your
body settles into this lovely low state of energy, the best
blood-pressure medicine you could ever hope for. REM sleep, on the other
hand, is sometimes known as paradoxical sleep, because the brain
patterns are identical to when you’re awake. It’s an incredibly active
brain state. Your heart and nervous system go through spurts of
activity: we’re still not exactly sure why.”
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Does the 90-minute cycle mean that so-called power naps are worthless?
“They can take the edge off basic sleepiness. But you need 90 minutes to
get to deep sleep, and one cycle isn’t enough to do all the work. You
need four or five cycles to get all the benefit.” Is it possible to have
too much sleep? This is unclear. “There is no good evidence at the
moment. But I do think 14 hours is too much. Too much water can kill
you, and too much food, and I think ultimately the same will prove to be
true for sleep.” How is it possible to tell if a person is
sleep-deprived? Walker thinks we should trust our instincts. Those who
would sleep on if their alarm clock was turned off are simply not
getting enough. Ditto those who need caffeine in the afternoon to stay
awake. “I see it all the time,” he says. “I get on a flight at 10am when
people should be at peak alert, and I look around, and half of the plane
has immediately fallen asleep.”
So what can the individual do? First, they should avoid pulling
“all-nighters”, at their desks or on the dancefloor. After being awake
for 19 hours, you’re as cognitively impaired as someone who is drunk.
Second, they should start thinking about sleep as a kind of work, like
going to the gym (with the key difference that it is both free and, if
you’re me, enjoyable). “People use alarms to wake up,” Walker says. “So
why don’t we have a bedtime alarm to tell us we’ve got half an hour,
that we should start cycling down?” We should start thinking of midnight
more in terms of its original meaning: as the middle of the night.
Schools should consider later starts for students; such delays correlate
with improved IQs. Companies should think about rewarding sleep.
Productivity will rise, and motivation, creativity and even levels of
honesty will be improved. Sleep can be measured using tracking devices,
and some far-sighted companies in the US already give employees time off
if they clock enough of it. Sleeping pills, by the way, are to be
avoided. Among other things, they can have a deleterious effect on memory.
Those who are focused on so-called “clean” sleep are determined to
outlaw mobiles and computers from the bedroom – and quite right, too,
given the effect of LED-emitting devices on melatonin, the
sleep-inducing hormone. Ultimately, though, Walker believes that
technology will be sleep’s saviour. “There is going to be a revolution
in the quantified self in industrial nations,” he says. “We will know
everything about our bodies from one day to the next in high fidelity.
That will be a seismic shift, and we will then start to develop methods
by which we can amplify different components of human sleep, and do that
from the bedside. Sleep will come to be seen as a preventive medicine.”
What questions does Walker still most want to answer? For a while, he is
quiet. “It’s so difficult,” he says, with a sigh. “There are so many. I
would still like to know where we go, psychologically and
physiologically, when we dream. Dreaming is the second state of human
consciousness, and we have only scratched the surface so far. But I
would also like to find out when sleep emerged. I like to posit a
ridiculous theory, which is: perhaps sleep did not evolve. Perhaps it
was the thing from which wakefulness emerged.” He laughs. “If I could
have some kind of medical Tardis and go back in time to look at that,
well, I would sleep better at night.”
• Why We Sleep: The New Science of Sleep and Dreams by Matthew Walker is
published by Allen Lane (£20). To order a copy for £17 go to
guardianbookshop.com or call 0330 333 6846. Free UK p&p over £10, online
orders only. Phone orders min p&p of £1.99
Sleep in numbers
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■ Two-thirds of adults in developed nations fail to obtain the nightly
eight hours of sleep recommended by the World Health Organisation.
■ An adult sleeping only 6.75 hours a night would be predicted to live
only to their early 60s without medical intervention.
■ A 2013 study reported that men who slept too little had a sperm count
29% lower than those who regularly get a full and restful night’s sleep.
■ If you drive a car when you have had less than five hours’ sleep, you
are 4.3 times more likely to be involved in a crash. If you drive having
had four hours, you are 11.5 times more likely to be involved in an
accident.
■ A hot bath aids sleep not because it makes you warm, but because your
dilated blood vessels radiate inner heat, and your core body temperature
drops. To successfully initiate sleep, your core temperature needs to
drop about 1C.
■ The time taken to reach physical exhaustion by athletes who obtain
anything less than eight hours of sleep, and especially less than six
hours, drops by 10-30%.
■ There are now more than 100 diagnosed sleep disorders, of which
insomnia is the most common.
■ Morning types, who prefer to awake at or around dawn, make up about
40% of the population. Evening types, who prefer to go to bed late and
wake up late, account for about 30%. The remaining 30% lie somewhere in
between.