A GREAT deal of anxiety is being expressed over children not getting enough sleep, usually because of lax bedtimes, watching too much TV and playing video games. Teachers and parents worry sleep-deprived children will be too tired to perform at school and irritable at home. 快猫短视频s worry kids are becoming fat: according to recent research, sleep-deprived children are twice as likely to be obese.

As just one example of sleep anxiety, a recent British warned of an 鈥渆pidemic鈥� of sleeplessness among children aged 5 to 15. It claimed that two-thirds of them are being turned into 鈥渮ombies鈥� by late-night gaming, television, YouTube and cellphone use, and it warned of the consequences for their waistlines. The survey was carried out for the UK hotel chain Travelodge 鈥� self-styled 鈥渞etailer of sleep鈥� 鈥� and it was not published in a peer-reviewed journal. It still found its way into .

The story of an epidemic of sleep-deprived zombie children is neat and appealing, but it quickly falls apart. There is little evidence that children are sleeping less than before. And the link between sleep deprivation and obesity has been greatly exaggerated.

鈥淭he story of an epidemic of sleep-deprived zombie children is both neat and appealing鈥�

Sleepy children are not a new concern. A hundred or so years ago, things were just as bad or even worse, though the culprit back then was too much homework. In 1884, the British Medical Journal reported that the influential psychiatrist James Crichton-Browne had testified to the UK parliament: 鈥淚 have encountered many lamentable instances of derangement of health, diseases of the brain, and even death resulting from enforced evening study in the case of young children, with the nervous excitement and loss of sleep which it so often induces.鈥�

His words were ignored but he did not give up. In 1908, in his presidential address to the Child Study Society, Crichton-Browne (by then ennobled) bemoaned that 鈥渢he evil of insufficient sleep in children is widespread鈥�.

He was responding to a talk by educational pioneer Alice Ravenhill, who described her long investigation into the sleep of 6000 elementary school children. She found that children aged between 3 and 5 years slept for 10 hours, 45 minutes a night, on average, while for 13-year-olds it was 8 hours (both of which are pretty much the same today). This, she said, was not enough. Having 鈥渃onsulted the best authorities鈥�, she advocated 13 hours鈥� sleep for the younger group and 11 hours for the older.

Soon afterwards, in 1913, Lewis Terman and Adeline Hocking from Stanford University, California, reported similar sleep durations among US school children. They found an average of 11 hours for 6-year-olds and 9 hours for 13-year-olds.

Fast forward to today, and little has changed. A survey of 11,500 children by Peter Blair and colleagues at the University of Bristol, UK, found that 6-year-olds sleep 11.3 hours on average, while 10-year-olds sleep 10.5 hours (Sleep, vol 35, p 353).

Although there were wide variations among the children, they concluded that 鈥渃ompared with earlier studies, the younger children鈥� slept for a shorter period鈥�. Nevertheless, both these values are greater than those from 1908 and similar to Terman and Hocking鈥檚 results in 1913.

Yet another study, by a team at the University of South Australia in Adelaide, looked at records going back to 1897 and found that children鈥檚 average sleep time has been steadily declining for the past century 鈥� though only at a rate of 43 seconds per year, or 1 hour and 20 minutes in total.

Intriguingly, the team also found that children consistently slept for about 37 minutes less than health professionals thought best at the time, and that the blame was invariably put on children being 鈥渙vertaxed by the stimulation of modern living鈥�. This suggests that sleep recommendations start with the assumption that children don鈥檛 get enough sleep, rather than an empirical assessment of how much they actually need.

If children are no more sleep-deprived today than they ever were, then maybe claims that too little sleep leads to obesity are also exaggerated.

Several studies have reported that children who sleep less are fatter. One, for example, found that 7-year-olds sleeping less than 10 hours a night are twice as likely to be obese than longer sleepers (). That sounds alarming, but 鈥渢wice as likely鈥� obscures the fact that the absolute numbers are small. Only around 10 per cent of the shorter sleepers are obese, compared with 5 per cent for those sleeping over 10 hours. Put differently, the vast majority of short sleepers are not obese. What is more, there is only about 30 minutes鈥� difference in the sleep of obese children versus those of normal weight.

If short sleep does cause obesity, then the effect is moderate at best, amounting to the accumulation of less than half a kilogram of extra fat per year as a result of hundreds of hours of accumulated 鈥渓ost sleep鈥�. I estimate that rather than sleeping for an extra hour or more, obese children could obtain the same effect with only 10 minutes of extra exercise each day.

So how much should children sleep? It is difficult to say because of large individual variation in requirements. As a rule of thumb, a child who has had enough sleep can get up fairly easily in the morning, is happy, alert, able to concentrate for most of the day and not too grouchy.

Paradoxically, children with persistently poor sleep may not seem sleepy but instead irritable, overactive, in need of constant stimulation and unable to concentrate 鈥� a state rather like mild attention-deficit hyperactivity disorder. Inadequate sleep may be a small contributor to childhood obesity, but the case is far from made.

Plus 莽a change. Claims of widespread sleep deprivation in western society are nothing new 鈥� in 1894, the British Medical Journal ran an editorial warning that the 鈥渉urry and excitement鈥� of modern life was leading to an epidemic of insomnia.

Even then it probably wasn鈥檛 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鈥檚 not to say that sleep deprivation doesn鈥檛 exist. But in general we鈥檝e 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 7陆 hours a night.

The well-known 鈥渇act鈥� 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 9 hours 鈥� though this applied to children aged 8 to 17, not adults. Even today, children continue to average this amount.

More support for today鈥檚 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 鈥渞elax, close your eyes and try to go to sleep鈥�. 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 9 or 10 hours a night. It is 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 鈥� the Saturday morning lie-in, the Sunday afternoon snooze 鈥� it doesn鈥檛 necessarily follow that we really need the extra sleep. Why shouldn鈥檛 we be able to sleep to excess, for indulgence? After all, we enthusiastically eat and drink well beyond our biological needs. Why shouldn鈥檛 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 鈥� 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 6 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鈥檚 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鈥� 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 5 hours a day, which applies to only 5 per cent of the population, and even then the problem is minimal. Somebody sleeping 5 hours every night would only gain a kilogram 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.

In truth, few obese adults are short-sleepers, and few short-sleeping adults are obese. The Nurses鈥� Health Study also revealed that people sleeping more than 9 hours a night are just as likely as short-sleepers to be fat.

The link between sleep shortage and obesity has also been found in children, though again the findings have been overstated. In one classic study of 5-year-olds, children who slept under 10 hours a night were more than twice as likely to be obese as those who slept for more, which sounds worrying (International Journal of Obesity, vol 16, p 721). But the actual numbers are small 鈥� 7.7 per cent versus 3.6 per cent. Similarly, while obese children sleep less on average than children of normal weight, the difference is very small 鈥� around 14 minutes.

The link between short sleep and diabetes has also been overcooked. It鈥檚 true that lean, healthy young adults who are restricted to 4 hours鈥� sleep a night for several nights show the beginnings of glucose intolerance and metabolic syndrome, which can be a precursor to type 2 diabetes (). However, that doesn鈥檛 mean it happens in the real world.

For one thing, the effect quickly reverses after one night of recovery sleep. Moreover, 4 hours鈥� sleep is highly artificial and the vast majority of people cannot sustain it for more than a few days. Our very lowest natural limit seems to be 5 hours, yet the researchers did not test the effect of 5 hours鈥� sleep on metabolism, and many have just assumed that what is found with 4 hours鈥� sleep applies to short sleep in general.

Not only have chronic sleep deprivation and its consequences been overstated, I also believe that our apparent desire for more sleep isn鈥檛 all it seems. Do we really mean it when we say 鈥測es鈥� to the question, 鈥淲ould you like more sleep?鈥� It鈥檚 a leading question that invites a positive response, in the same way as asking whether you would like more money, a bigger house or more holiday. Who, in all honesty, would say no?

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.

My team recently investigated these questions by giving around 11,000 adults a questionnaire asking indirectly about perceived sleep shortfall. We did this by asking when they usually went to sleep and at what time they woke up, followed by, 鈥淗ow much sleep do you feel you need each night?鈥� The difference between the two gave an estimate of the shortfall. They also completed a standard questionnaire to assess daytime sleepiness ().

Half the respondents turned out to have a sleep shortfall, averaging 25 minutes a night, and around 20 per cent had excessive daytime sleepiness. However, the people with a sleep deficit were no more likely to experience daytime sleepiness than those without.

To gauge the respondents鈥� determination to make up their perceived sleep debt, we then asked, 鈥淚f you had an extra hour a day, how would you prefer to spend it?鈥� The alternatives were playing sport or exercising, socialising, reading or relaxing, watching TV or listening to the radio, working, sleeping, and 鈥渙ther鈥�.

Only a handful of people opted to use their extra hour for sleep. It seems that wanting more sleep is not necessarily synonymous with needing more sleep, and that given a choice, people will happily forego extra sleep in favour of other leisure activities.

聯Given a choice, people will happily forego extra sleep in favour of other leisure activities聰

Does any of this matter? I believe it does. Propagating the myth of a chronically sleep-deprived society is not only intellectually lazy, but further adds to the anxieties of people who believe they are not getting enough, creating unfounded health concerns and a greater demand for sleeping pills. Instead of worrying that we鈥檙e not getting enough sleep, we should acknowledge that we鈥檙e probably sleeping better than ever before 鈥� and rather than trying to increase our sleep, maybe spend those 鈥渆xtra鈥� hours of wakefulness doing something more productive.