Every US citizen spends on average 8,22 hours every day in bed. The findings of the institute for statistics are almost the same as those of scientists. The usual time of sleep for an adult person is between 6 and 9,5 hours.
How much sleep do you need?
Some doctors specialized on sleep recommend 7 to 8 hours of sleep, not less, not more. They say that this amount of sleep has the best results on health and well-being, therefore making us live longer and healthier. But it is not possible to create a nominal amount of sleep for the individual from this, because also in sleep we encounter a lot of exceptions from the rules.
Naturally, some people sleep longer or shorter than average, people with good and bad sleeping habits, people who are more active in the morning or in the evening.
There is one question that everyone who suffers from sleeping problems asks himself every morning: how many hours did I sleep tonight or how many hours of actual sleep did I collect during this long night?
You won’t hear about any magic formula of 8 hours of sleep from any sleep expert. While actually most normal sleepers really spend 7 to 8 hours sleeping, some people already feel fresh and recovered after 4 to 5 hours and some others who need 9 to 10 hours to really feel satisfied.
In reality, people who usually sleep 4 to 5 hours spend about the same time in deep sleep as the average sleeper manages to spend during his 8 hours.
Albert Einstein is said to have had the habit of sleeping 14 hours and still revolutionized the modern world with his theory of relativity.
Napoleon, on the other hand, is said to have spent no more than 4 hours daily with sleeping, the rest of the time he preferred to spend conquering Europe.
Some people function better in the morning or in the evening and therefore should sleep at different times of the day, to really feel recovered. In the case of some specific sleeping problems, people might even sleep 10 to 12 hours and still feel tired and without energy on the next day. The amount of sleep and individual sleeping habits – often a result of education – show therefore quite a significant variation: it is not the number of hours that count, but the stability of the sleep profile and adaptation to the own biological rhythm.
A maybe weak consolation for people who have sleeping problems: if they are not the consequence of any organic issues, they don’t cause any physical illnesses (even though the person often feels like that). Also, sleep deprivation for several days (the world record is 11 days) does not cause irreversible physical damage. Obviously that
doesn’t change the fact that the person feels terrible, very sensible, unsatisfied, and without energy.
Changes in sleep with raising the age
Sleeping habits and needs can differ a lot from individual to individual. But the most significant changes can be observed when comparing different age groups. While a newborn child may spend about 20 hours of the day with sleeping, on average, that amount of time is reduced during childhood and adolescence to 8 hours. Past the fifties of human life, the amount of sleep can fall even more.
Not only the amount of sleep but also the sleeping architecture is changed with rising age: they spend less time in deep sleep and REM phases (some old people hardly reach deep sleep at all), and they wake up more frequently during the night.
Sleep becomes more fractured and superficial, the rhythm of sleep and being awake becomes less regular. The need for taking a nap during the day becomes more intense. The natural consequence is that older people start to regard sleep more and more as something problematic. But in reality, often these changes are typical processes, of biological origin, not any disease at all. Regarding this aspect, the investigation has proven that it is possible to interfere in such processes of change (similar to, i.e., in the case of physical fitness).
Older people, who are active with their body and mind, have a daily routine and plan their objectives, usually have a much better sleep than people of the same age, who are used to a passive, dull day, almost set into „standby.“
Sleeping and waking as a biological rhythm
„Sleep means for the whole man what means winding up for the
clock.“ (A. Schopenhauer)
You’ve probably taken notice after some nights with good sleep, that how you’re feeling during the day also depends on variations, which have nothing to do with the quality of sleep of the preceding night.
Even after a night that didn’t let you sleep at all, you can often observe yourself feeling less tired as the morning advanced, and than in the evening, you will return to feeling even more tired.
These variations are due to our so-called „inner clocks,“ which cause us directly to feel more or less tired, they even control other sensations, like hunger. Also, being able to wake up at the same time, to the point that some people don’t even need an alarm clock, is possible thanks to these „inner clocks“ in our brain. They control most of our biological rhythms. Body temperature, i.e., varies about +/–1 degree Celsius over the cycle of one day. During the day, it slowly rises and reaches the highest point in the afternoon. In the evening it lowers and reaches its lowest point in the early morning.
The inner clock that controls our rhythm of temperature also controls most of our sleep-wake-rhythm.
As the curve of temperature begins to fall in the evening, we start to feel tired. As it rises in the morning, the organism is activated, and we wake up.
That’s why someone who has been to a party, for example, and only goes to bed in the early morning wakes typically up again after only a few hours. Even though the time of sleep might have been insufficient, the raising body temperature doesn’t allow the person to continue to sleep and starts activating the body and its biological rhythm progresses. The inverse happens when someone tries to go to bed much earlier than usual. Usually, that attempt will fail, as the body is still much too active, its „operating temperature“ is still much too high.
The evening type
For some people, this very tight connection between body temperature and sleep-awake-rhythm can be problematic: In the case of the so-called „evening type,“ the temperature only reaches its maximum value about one or two hours later and then starts to fall only very slowly. They can work particularly well in the evening but have trouble sleeping because they take time to become tired. Following their natural rhythm, they’d probably only go to bed around midnight. But if they need to wake up the next morning at 7 o’clock, their body temperature has only just passed its minimum slightly. Therefore they don’t feel perfect, need a long time to wake up, have a bad temper during the morning, and only become interested in breakfast very late.
The morning type
On the other hand, the so-called „morning type“can work particularly well in the morning, as the body temperature has already reached its average values. Opposed to „evening types,“ the „morning type“ has to deal with the fact that body temperature will
reach its maximum in the afternoon and fall very fast in the evening. They become tired very early in the evening and can’t really do anything useful anymore.
The „evening type“ usually can have problems being able to fall asleep and the „morning type“often can have trouble being able to sleep for a whole night or wake up too early in the morning. The inner clock that controls our temperature rhythm, the sleep-wake- rhythm and other body functions (for example, hormone) follows more or less the 24-hour system.
During the day, we observe periods of 90 minutes according to which our performance keeps changing. Then there are other patterns of 4 hours, etc. If you suddenly feel tired in the morning, after lunch or in the late afternoon, it’s because of these patterns.
The harmonic interaction between different biological rhythms controls most of our biological and psychological functions.
An organized lifestyle can facilitate the process of falling asleep, as the body becomes used to falling asleep at the same time. Monotonous regularity is also important for the interaction of the different biological rhythms. Shift work and casual lifestyle (i.e.eating and going to sleep or waking up at irregular times) can upset these harmonic interactions. It’s like losing the beat. Sleeping problems and other biological problems (like digestive problems) can appear. A person having a normal sleep will also sometimes experience light sleep and can wake up several times. The quality of sleep is conditioned by various factors: age, lifestyle, activity during the day, individual sleep-awake-rhythm.