What a claim! Under pressure of time, after TV crime thrillers and professional emails until shortly before midnight, please let the blissful slumber begin immediately.
Seven hours of sleep should be enough, all the time of course, so that the fibre-deep tiredness gives way to a vital freshness in the morning, beautiful dreams included.
Interruptions are not intended, if you roll restlessly on the mattress for heavy side sleepers or even wake up several times, there must be something wrong with you, right?
Just this spring, a survey by a major health insurance company revealed that almost 80 percent of adults in Germany claim to suffer from sleep disorders, and around ten percent are even affected by chronic insomnia.
Perhaps the expectations are simply too high. After all, it is almost a miracle that the stressed cosmopolitan, despite marital quarrels and job crises, often finds himself falling asleep quite quickly, drifting off at a moment’s notice and setting everything to zero.
Moreover, from an evolutionary point of view, it may even make sense that sleep is interrupted again and again. This is the conclusion reached by anthropologists in the journal Proceedings of the Royal Society B.
The researchers around Charles Nunn of Duke University in Durham had studied the Hadza people in northern Tanzania and observed very different sleep times. The tribe traditionally lives in groups of 20 to 30 members, who still travel as hunter-gatherers.
In the Hadza people there is almost always someone awake. This serves the safety of all.
On average, the Hadza went to bed around 10 p.m. and woke up around seven. Their sleep patterns, however, were quite different and had not been synchronized within the group, as is sometimes suspected in peoples whose sleep is not influenced by technology and street lighting.
Some of the Hadza initially slept soundly for a few hours, others woke up soon after falling asleep and even left their camp for a short time. Some lay down early, others much later.
Throughout the night, there were only a few episodes of just one minute’s duration during which all the members of the group slept at the same time. Otherwise, about a third of the participants were active or sleeping only superficially at any time during the night.
“Older people in particular often complain that they wake up again and again during the night and can no longer fall asleep,” says Charles Nunn. “Perhaps we should not immediately consider this a sleep disorder, but rather a remnant from an earlier phase of our evolution where this behavior was beneficial.”
If all the members of a group sleep, the risk of falling victim to predators or predatory attacks is ultimately far greater. It is also known from some species living in groups that some have to stay awake at night in order to be able to report dangers early.
This type of night watchman has proven its worth in the wild. For the Hadza, it is not necessary to put someone on guard at night because someone is always awake anyway. In addition, the young stay up late and the old are back on their feet early.
If the grandparents have a shorter and interrupted sleep, this increases the security. Large differences in the sleep-wake rhythm therefore offer a survival advantage, but this only works in groups of twelve or more people.
The San people in southern Africa, for example, usually travel in groups of three, in which case they must alternate between nightly vigilance. For the inhabitants of the industrial nations living individually or in small families, however, the evolutionary advantage of the ancestors or African tribal groups is only a small consolation when they restlessly turn from one side to the other.
Instead of talking about the “advantage of poorly sleeping grandparents”, as the anthropologists around Charles Nunn do, the diagnosis is that of an “exhausted society” that calms down with tranquilizers and hardly wakes up at all, even during the day.
The impression of not having slept all night is usually deceptive. Those who think that they have hardly slept and that they have woken up again and again, in fact often end up with a net sleep duration of five and a half or six instead of the recommended seven hours.
Lying awake for “hours” then only extends over two or three times 20 minutes. By the way, looking at the clock again and again is not good advice on restless nights.
This increases the pressure to finally fall asleep. Whether you feel amazingly fit in the morning after a night with several interruptions or carry the leaden feeling with you until the afternoon depends on which phase you woke up in.
Being torn out of a deep sleep by baby cries or construction noise can paralyze the whole day.