Why Less Than 7 Hours Of Sleep Can Shorten Your Life

Photographed by Eylul Aslan.
So you think you get enough sleep, do you? Think you can exist on six, maybe seven hours a night? If, when your alarm goes off in the morning, you feel as though you could keep snoozing, then you’re likely not getting enough good quality sleep at night. If you can’t function without coffee before noon, you’re probably sleep-deprived. And if you’re sleep-deprived, you’re not alone: according to the World Health Organization, we are in the midst of a global sleep-deprivation epidemic.
Not getting enough shut-eye won’t just make you yawn on the Tube or wish for nap-time at your desk. According to one of the world’s leading sleep scientists, the less you sleep, the shorter your life will be. Matthew Walker is a professor of neuroscience and psychology at the University of California and he’s just published the definitive manifesto on sleep science, called Why We Sleep – out this week.
In this important, elegantly written and obsessively researched book, Walker lays out some astonishing facts about the importance of sleep. If you’ll excuse my decision to use this phrase, it’s a serious wake-up call that we need to take our sleep much more seriously – and fast. Sleep deprivation (that is, sleeping six hours or less a night or not getting the quality of sleep you require) is linked to Alzheimer’s disease, anxiety, depression, bipolar disorder, suicide, stroke, chronic pain, cancer, diabetes, heart attack, infertility, weight gain, obesity and immune deficiency. It can damage the brain, exacerbate mental illness, tempt serious physical illness, weaken the immune system, rile up the nervous system, erase concentration, deplete productivity, eradicate creativity, ravage the body and, in extreme cases, kill. The importance of sleep, quite seriously, cannot be overstated. It is, Walker says, more powerfully linked to our mortality than nutrition and exercise.
If you’d rather look at it in positive terms, sleep is the Swiss Army knife of medicine. It is a miraculous cure-all that, done properly, makes us live longer, enhances our memory, ignites our creativity, makes us more physically attractive, lowers our food cravings, regulates our emotions, protects us from cancer and dementia, staves off cold and flu, lowers our risk of stroke, diabetes and heart attack, and makes us happier, less depressed and less anxious.
So what, then, explains what Walker calls “society’s apathy towards sleep”? Why are we all so chronically under-slept, particularly when we know how important sleep is?
“Firstly, increased work hours, I think people are working longer to begin with,” says Walker. “Secondly, we know that actual commute times have also increased, so people are leaving their houses earlier, they’re coming home later, and they’re working longer in between too, all of which starts to squeeze sleep in this sort of vice grip and starts to pinch it down.”
Then there are our drugs of choice: “Caffeine consumption is obviously up. Caffeine is the second most traded commodity on the surface of the planet, would you believe, after oil, which tells you everything about the state of our sleep-deprived society. If there was a commercial metric of how sleep-deprived we are, it is probably that. Caffeine keeps us awake, it makes it harder to fall asleep, we all know that, but some people might not know caffeine also prevents you from getting good, deep sleep. So someone might say to me, 'I’m just one of those people who can have a coffee after dinner and I’m fine, I fall asleep and it’s no problem'. The problem is that even if you fall asleep, the depth of your sleep won’t be as deep as if you had abstained from coffee.”
So giving yourself a cut-off time of midday, or at the latest 2pm, for your last coffee of the day is sensible. As for our other most-beloved drug, alcohol, well, Walker says we shouldn’t be drinking at all at nighttime if we want to get the best possible snooze in.
“Alcohol is probably the most misunderstood of all chemicals we use for sleep,” he says. “People often say you can have a nightcap, you fall asleep more quickly – it’s actually incorrect because alcohol is a type of drug that we call a sedative and unfortunately sedation is not sleep, it’s very different and it doesn’t give you the benefits of sleep. So when people say they fall asleep more quickly when they’ve had a bit of whiskey, they’re losing consciousness but they’re not falling into a natural sleep. Alcohol also fragments your sleep throughout the night so you wake up many more times and wake the next morning feeling unrefreshed and unrestored. It blocks your dream sleep or your REM sleep, which is vital for many aspects of brain and body health, particularly emotional regulation and control.”
The other things keeping us awake are light, technology and heat. Since Thomas Edison invented the lightbulb, we have chased away the darkness that naturally tells us when to sleep. Computer and mobile phone screens also contribute to this diminishing of darkness, which we actually need to trigger the release of the hormone melatonin, which tells the body to sleep. That, and we are setting our air-conditioners too high. Most people tend to go for about 20 degrees Celsius on their radiators but that’s actually too hot to sleep properly. Sleep requires a little cool – something more like 18 degrees Celsius. It also requires regularity – we should be going to bed and waking up at the same time each day, no matter what – but we rebel against this rule flagrantly.
Underscoring all these logistical factors is a dangerous disrespect for the act of sleeping. We tend to associate sleep with slothfulness, dismissing people who sleep eight hours or more a night as lazy, rather than sensible, as they are. We shame teenagers for sleeping in, shun night owls for their natural sleep cycles, tease habitual nappers and roll our eyes at anyone who wants to get an early night. We simply do not appreciate how important sleep is – in fact, we seem to celebrate sleep deprivation like it’s noble or remarkable in some way. It is not. It is dangerous and life-threatening.
Reading Walker’s book has shocked me into prioritising my own sleep more. I, for one, will be trying to lock in regular bedtimes, regulating my coffee intake, working on making my office hours sensible, switching off my phone an hour before bed, and checking my room temperature and my attitude. I’d suggest you do the same. Good luck, and sweet dreams.
Why We Sleep by Matthew Walker is out now.

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