Why We Sleep by Matthew Walker review – how more sleep can save your life

Awake at 4.30am the other morning, having been roused from sleep by my four-year-old son climbing into bed with my wife and me (a more or less nightly occurrence), I found myself sitting up and reading about the effects of insufficient sleep. It has been making me stupider, fatter, unhappier, poorer, sicker, worse at sex, as well as more likely to get cancer, Alzheimer’s and to die in a car crash. At the same time, my lack of sleep has been slowly but inexorably shrinking a) my chances of living into my mid 60s, b) my testicles.

Why We Sleep by the neuroscientist Matthew Walker – my ill-chosen small-hours reading material – is filled with startling information about the effects of suboptimal shut-eye levels. It’s not a book you should even be thinking about in bed, let alone reading. If it weren’t too unsettling to permit sleep in the first place, it would be the stuff of nightmares. The marginalia in my review copy, scrawled in the wavering hand of a man receiving dark intimations of his own terrible fate – “OMFG”; “This is extremely bad!” – might seem less appropriate to an affably written popular science book than to some kind of arcane Lovecraftian grimoire.

Walker’s title is misleading – as he himself states in the early pages, it suggests that there might be only one reason why we sleep. In fact, he presents sleep as a panacea for a bewildering array of conditions that would otherwise cause the slow deterioration of body and mind. In one playful passage, he describes it as though he were marketing a new pharmaceutical:

Scientists have discovered a revolutionary new treatment that makes you live longer. It enhances your memory, makes you more attractive. It keeps you slim and lowers food cravings. It protects you from cancer and dementia. It wards off colds and flu. It lowers your risk of heart attacks and stroke, not to mention diabetes. You’ll even feel happier, less depressed, and less anxious. Are you interested?

Well, yes, I for one am keenly interested in this wonder drug; the problem, though, is getting your hands on the stuff. Being kneed in the spine by a four-year-old in the dead of night turns out to be the least of it; by the time I’d finished Walker’s book, the whole of modernity lay revealed to me as a vast, many tentacled conspiracy against sleep. One of the book’s real strengths is how clearly it elucidates the extent of the damage wrought by our collective ignorance of the importance and complexity of sleep’s role in our lives, and the difficulty encountered by many of us in getting any.

In terms of our natural sleeping tendencies, people can be divided into two broad groups, or “chronotypes”: morning larks and night owls. Each group operates along different circadian lines, and there is pretty much nothing owls can do to become larks – which is tough luck, because work and school scheduling overwhelmingly favour early risers. Owls are often forced, he writes, “to burn the proverbial candle at both ends. Greater ill health caused by a lack of sleep therefore befalls owls, including higher rates of depression, anxiety, diabetes, cancer, heart attack and stroke.”

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“The importance of insomnia is so colossal that I am tempted to define man as the animal who cannot sleep,” wrote EM Cioran, the patron saint of night owls whose weary visage kept floating into my mind as I read Why We Sleep. Walker’s worldview may not be as bleak as that of the Romanian essayist, but he does paint an intolerably grim portrait of a society in which an increasingly large proportion of us are getting a decreasing amount of sleep. What he calls our “cultural sleep norms” are under assault on multiple fronts:

Midnight is no longer ‘mid night’. For many of us, midnight is usually the time when we consider checking our email one last time – and we know what often happens in the protracted thereafter. Compounding the problem, we do not then sleep any longer into the morning hours to accommodate these later sleep-onset times. We cannot. Our circadian biology, and the insatiable early-morning demands of a post-industrial way of life, denies us the sleep we vitally need.

Basically, if you’re regularly clocking in at under seven hours a night, you’re doing yourself a disservice as grave as that of regularly smoking or drinking to excess. And as someone who tends to chalk up six hours as a solid victory, and who feels – or at least felt before reading this book – that he can get by on five, I was especially disturbed by the revelation that sleep-deprived people often don’t recognise themselves as such.

That low level exhaustion becomes their accepted norm, or baseline. Individuals fail to recognise how their perennial state of sleep deficiency has come to compromise their mental aptitude and physical vitality, including the slow accumulation of ill health. A link between the former and the latter is rarely made in their mind.

The book bears a sobering and vital message, too, about the centrality of sleep to the proper development of young minds. Early school starting times – particularly in the US, where, barbarically, almost half of public high schools start before 7.20am – are disastrous for the mental health of teenagers. There is serious evidence, Walker suggests, for viewing lack of sleep as a factor in the onset of depression and schizophrenia.

Despite the direness of his warning, Walker’s tone is mostly chipper and likable in the standard pop-sci style, and he is excellent at explaining complex neurological phenomena for a general readership. He does occasionally get bogged down in ill-advised wordplay (here he is on marine mammals and REM sleep, for example: “Seals in the ocean will sample but a soupçon of the stuff”). There is also a deeply weird passage that attempts, via “The Sound of Silence”, to explain sleep’s benefits to memory, but which really only demonstrates how badly a paragraph can fall victim to what I assume are the reprint restrictions on Simon and Garfunkel lyrics. “Perhaps you know the song and lyrics,” beseeches Walker. “Simon and Garfunkel describe meeting their old friend, darkness (sleep). They speak of relaying the day’s events to the sleeping brain at night in the form of a vision, softly creeping – a gentle information upload, if you will.”

But I suppose it’s churlish to take issue with the prose of a person who is trying to save you from an existence of exhaustion and misery, terminating in early death – a bit like grumbling about insufficient legroom in a life raft. Because that’s what this book is. It’s probably a little too soon to tell you that Why We Sleep saved my life, but I can tell you that it’s been an eye-opener.