Sleep Debt - An urban myth or a social problem?Many sleep researchers believe today’s society is one of chronic sleeplessness. Others aren’t so sure. There’s a folk understanding of “sleep debt”, when people haven’t had enough sleep. The unarticulated idea is that this is somewhat like a financial account, and that a built-up debt must be repayed. Indeed, people do sleep longer on weekends than on weekdays. But the popular understanding of sleep debt is not wholly accurate. For starters, it is not a straight balance. Even after serious sleep deprivation, most people usually need only two or three good nights’ sleep to get back to normal. If you run short one hour per night for 5 nights in a row (say Sunday through Thursday), you don’t necessarily need 5 extra hours on the weekend. Another exaggeration or misconception, according to some dissident sleep experts, is that we as a society get a lot less sleep than we used to. Jim Horne of Loughborough University points out that intelligent animals such as bears and tigers sleep much more in captivity than in the wild. Since it is unlikely that they are sleep-deprived in the wild, other factor(s) must account for their sleepiness when penned up, such as boredom. Horne, who is one of the foremost sleep researchers in the world, compares the situation to hunger. Asked if they are hungry, people may say no - but the same people in the same situation in a restaurant with the smell of food and other people eating – those same people will feel hungry. Context matters a lot Similarly, people may not feel particularly sleepy near their regular bedtime, but once they lie down may fall asleep within a normal period of time. Similarly, the Inuit (Eskimos) traditionally spent the long Arctic winter nights by sleeping for 14 hours a day, compared with around six hours daily during the continuous summer light. Despite the eight-hour seasonal difference, the Inuit did not suffer from sleep deprivation in the summer, as the key sign of insufficient sleep - excessive daytime drowsiness - was absent. Now that they have adopted a modern lifestyle, Inuit people tend to sleep about the same length of time as other people. In a recent article in the Journal Sleep, Horne argues that sleep debt is largely a myth and that the average healthy adult needs only 7 to 7.5 hours of sleep per day. He suggests that most people would get more out of a 15-minute afternoon nap than an extra hour of sleep at night. Horne told the BBC: "The test of insufficient sleep is whether you are sleepy in the day or if you remain alert through most of the day." Article. David Dinges of the University of Pennsylvania raises objections to Horne’s arguments, although he concedes that there is little hard scientific evidence on sleep debt in the general population. Indeed, sleep debt experiments have really been sleep deprivation experiments and with a limited number of participants. Also, they measure the effects of sleep deprivation through cognitive tests designed to measure mental performance. It is not clear that everyone needs to be at peak mental conditions all the time. It is fairly clear that there can be such a thing as “REM debt”. When people are selectively woken at the start of their REM periods a repeated number of times, they spend a lot more time in REM when they are finally allowed to sleep uninterruptedly.
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"O Sleep, rest of all things, mildest of the gods, balm of the soul..." (Iris to Hypnos. Ovid, Metamorphoses) |