Sleep deprivation claims often overblown
Ask people whether they’d like more sleep, and most will say yes. Does that mean they’re not sleeping enough? The apparent desire for more shut-eye, together with oft-repeated assertions that our grandparents slept longer, all too easily leads to the conclusion that we in the United States are chronically sleep-deprived. Adding to these concerns are recent claims that inadequate sleep causes obesity and related disorders, such as diabetes.
Claims of widespread sleep deprivation in Western society are nothing new — in 1894, the British Medical Journal ran an editorial warning that the “hurry and excitement” of modern life was leading to an epidemic of insomnia.
Even then it probably wasn’t true. The fact is that most adults get enough sleep, and our collective sleep debt, if it exists at all, has not worsened in recent times. Moreover, claims that sleep deprivation is contributing to obesity and diabetes have been overblown.
My assertion is that the vast majority of people sleep perfectly adequately. That’s not to say that sleep deprivation doesn’t exist. But in general we’ve never had it so good.
Over the past 40 years, there have been several large studies of how much sleep people actually get, and the findings have consistently shown that healthy adults sleep 7 to 7z hours a night.
The well-known “fact” that people used to sleep around 9 hours a night is a myth.
The figure originates from a 1913 study by researchers at Stanford University in California, which did find that average daily sleep was nine hours — though this applied to children ages 8 to 17, not adults. Even today, children continue to average this amount.
More support for today’s epidemic of sleep debt supposedly comes from laboratory studies using very sensitive tests of sleepiness, such as the multiple sleep latency test, in which participants are sent to a quiet, dimly lit bedroom and instructed to “relax, close your eyes and try to go to sleep.” These tests claim to reveal high levels of sleepiness in the general population, but as they are performed under relaxing conditions they are able to eke out the very last quantum of sleepiness, which, under everyday conditions, is largely unnoticeable.
Another line of evidence trotted out for chronic sleep deprivation is that we typically sleep longer on vacation and at weekends, often up to 10 hours a night. It’s often assumed that we do this to pay off a sleep debt built up during the week.
However, just because we can easily sleep beyond our usual daily norm — the Saturday morning lie-in, the Sunday afternoon snooze — it doesn’t necessarily follow that we really need the extra sleep. Why shouldn’t we be able to sleep to excess, for indulgence?
After all, we enthusiastically eat and drink well beyond our biological needs. Why shouldn’t it be the same with sleep?
Most mammals will sleep for longer than normal if overfed, caged or bored. The three-toed sloth is a good example. Sloths kept in zoos sleep around 16 hours a day — yet in their natural, wild state they sleep less than 10. Niels Rattenborg and colleagues at the Max Planck Institute for Ornithology in Starnberg, Germany, recently found this out by using miniature EEG recorders attached to the heads of sloths in Panama, the first such experiment on a free-ranging wild animal.
Why this difference in its sleep? The most likely explanation is that sloths simply sleep to excess when caged. This is seen in domestic animals, too. Sheep in pens, horses in stables and cows in barns sleep much more than when in open fields, and pet cats sleep extensively compared with feral cats.
Until recently, people living above the Arctic Circle slept much longer in winter than in summer. There are reports from the 1950s of Inuit sleeping up to 14 hours a day during the darkest months compared with only six in the summertime. Given the opportunity, we can all learn to significantly increase daily sleep on a more or less permanent basis. When it is cut back to normal we are sleepy for a few days, and then the sleepiness disappears.
Far from our being chronically sleep-deprived, things have never been better. Compare today’s sleeping conditions with those of a typical worker of 150 years ago, who toiled for 14 hours a day, six days a week, then went home to an impoverished, cold, damp, noisy house and shared a bed not only with the rest of the family but with bedbugs and fleas.
What of the risk of a sleep shortage causing obesity? Several studies have found a link, including the Nurses’ Health Study, which tracked 68,000 women for 16 years.
The hazard, though real, is hardly anything to worry about. It only becomes apparent when habitual sleep is below five hours a day, which applies to only 5 percent of the population, and even then the problem is minimal. Somebody sleeping five hours every night would only gain about two pounds or so of fat per year. To put it in perspective, you could lose weight at the same rate by reducing your food intake by about 30 calories per day, equivalent to about one bite of a muffin, or by exercising gently for 30 minutes a week.
The acid test of inadequate sleep is excessive daytime sleepiness. Another way to expose the truth is to gauge to what extent those who say they want more sleep would actually sacrifice other desirable activities.
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