How sleep could save your life

Matthew Walker has spent two decades studying how sleep affects the human mind and body. His conclusion? The modern reluctance to go to bed is making us fat, ill and miserable. Rachel Cooke reports on a hidden epidemic

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. “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. Indeed, it is Walker’s 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.

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, cancer, diabetes, obesity and anxiety, they will try harder to get the recommended eight hours a night. But the individual can only achieve 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. “And yet no one is doing anything about it. When have you ever seen an NHS poster urging sleep? When did a doctor prescribe not sleeping pills, but sleep itself? Sleep loss costs the UK economy more than £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.”

Why, exactly, are we so sleep-deprived? In 1942, less than 8% of the population was trying to survive on six hours or less of sleep a night; in 2017, almost one in two people is. “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 of these are the enemies of sleep.” Walker believes, too, that in the developed world sleep is 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. 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 of sleep.’ 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 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. He started out studying for a medical degree, but switched to neuroscience and, after graduation, began a PHD in neurophysiology. 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 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 following six months, Walker taught himself how to set up a sleep laboratory and, sure enough, he found a clear difference between patients. Sleep, it seemed, could be a new early diagnostic litmus test for different subtypes of dementia.

After this, sleep became his obsession. “Only then did I ask: what is this thing called sleep, and what does it do?” 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

“More than 20 large-scale studies report the same clear finding: the shorter your sleep, the shorter your life”

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%, how could you not?”

Should his eyelids fail to close, Walker admits that he can be a touch 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. “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.

More than 20 large-scale epidemiological studies all report the same clear finding: 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. 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, thus causing 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. But processed food and sedentary lifestyles do not adequately explain its rise. Something is missing. It’s now clear that sleep is that third ingredient.”

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. As Walker has already said, studies show that short sleep can affect our cancerfighting immune cells. And getting too little sleep across the adult lifespan will also 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 lessens our ability to remove them. 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.)

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). He suggests that dreaming is a soothing balm. 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.

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. 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 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.”

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. Second, they should start thinking about sleep as a kind of work, like going to the gym. “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. Sleeping pills, by the way, are to be avoided. Among other things, they can have a deleterious effect on memory.

What questions does Walker still most want to answer? “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.”

A longer version of this article first appeared in The Observer © Guardian News and Media Limited 2017. Why We Sleep: The New Science of Sleep and Dreams by Matthew Walker is published by Allen Lane at £20.

“During NREM sleep, your brain goes into this incredible synchronised pattern of chanting, the cells all singing together”