Why do we sleep

Going to sleep relieves mental and emotional stress and relaxes tired muscles. To go to bed and sleep will make up for life's difficulties. Overall, we overslept around a third of our lives - a third that we don't remember, except that sometimes fragmentary fragments of dreams get stuck for a while. Rest and activity phases can already be found in bacteria and insects. Even body cells “sleep” and “wake up”, as certain genes are only switched on and off at certain times. Our sleep-wake behavior follows a rhythm that is subject to the whole of life.

Rhythmic consonance
The phenomenon of spontaneous synchronization is widespread in nature. Fireflies, for example, switch their lights on at the same time as dusk falls. If two firefly men fly close enough to each other, they synchronize their glow. They blink in unison, so to speak, in order to increase the success of mating with their female mates. The example of the spontaneous synchronization of two pendulum clocks, which the mathematician and physicist Christiaan Huygens was the first to discover in the 17th century, is also impressive: If two pendulum clocks are next to each other, the pendulums fall from a parallel movement pattern into a rhythm in which they become evenly - and move apart. One pendulum behaves like the mirror image of the other. It is similar with our sleep-wake rhythm: We believe that we control it consciously by going to sleep at night and waking up in the morning with the alarm clock. In fact, there is a spontaneous synchronization of the sleep-wake change with the light-dark or the day-night change. Instead of half an hour as is the case with pendulum clocks, humans need roughly the entire first year of their lives for this coordination to be balanced. Some make it earlier, some later. The synchronization of the sleep-wake with the day-night change does not happen passively, but is actively controlled by a pin-sized brain area. The clock sits in the head and, similar to a pacemaker, sets a clock - in this case a 24-hour clock, which in technical jargon is called a "circadian" clock (from Latin "circa diem", about a day). In addition to sleep, this clock controls practically all rhythmic day-night phenomena in our body. The liver is different during the day than at night (which is important for the breakdown of alcohol in the blood). Heartbeat, blood pressure and body temperature are dictated by the brain clock. Many hormones such as melatonin or cortisol show daily fluctuations. Our well-being, mental performance and mood also fluctuate every 24 hours. However, we only feel this influence when we lead a “modern” life, for example when we have to fly to distant countries (jet lag) or do shift work: lifestyles that are increasingly common in our society and whose consequences for human health are still increasing little attention is paid to them. Jet lag and shift work always result in a «desynchronization» between the day-night and sleep-wake changes - the rhythmic harmony is massively disturbed. Shift workers suffer from permanent jet lag, so they are travelers who never arrive in the new time zone. So with them sleep is the first thing that is disturbed. Surveys have shown that over 70% of shift workers have problems sleeping and these persist even after they retire. A persistent disruption of the synchronization of the circadian conductor with the day-night change leads in the long term to sleep disorders and numerous other complaints such as cardiovascular problems, daytime tiredness, obesity and even severe depression. For this reason, the WHO has classified shift work as hazardous to health and potentially carcinogenic. At least flight crews and shift workers are more likely to develop cancer than day workers. Animal experiments have shown that mice whose internal clock is out of step develop tumors more quickly and die earlier than their conspecifics who are not trained to work shifts. Just as there are tall and short, fat and thin, red-haired and blonde people, there are also short and late sleepers, early and late sleepers as well as deep and superficial sleepers. Everyone has their own individual sleep behavior, some of which is inherited over generations and also passed on culturally. Just as we can artificially change the innate hair color or turn gray with age, we adapt our sleep needs to everyday work or perhaps suffer from senile bed escape. In other words: we can or must coordinate our sleep-wake rhythm with the socially imposed working hours. Because of the early start of school in Switzerland, young people in particular are forced to do this, which most people find very difficult due to their mostly later chronotype in puberty. Instead of schools, the senior universities should start early, as the peak of intellectual performance in old age shifts more and more into the morning, while young people often reach their top form in the evening. There is great potential for employees and employers in optimizing school and working hours according to the individual circadian rhythm. The chronotype and sleep type factors can play a major role in the design of the shift schedule, in order to keep the employees' sleep as relaxing as possible and their error rate as low as possible. An impressive example is the use of so-called "chronotherapy", in which drugs are dosed and "timed" according to the individual circadian rhythm, which leads to significantly higher chances of survival for cancer patients.

Night symphony
Since the discovery of brain wave measurement by the neurologist Hans Berger in the 1920s, it has been clear that the brain is always active and vibrates in different rhythms. The most famous of these, named after Berger, is a synchronous oscillation pattern of the brain waves that repeats itself six to nine times per second and occurs while awake with eyes closed. This pattern changes continuously from being awake to falling asleep to deep sleep, from a rapidly paced, superficial waking rhythm to a slow and sweeping rhythm in deep sleep. In the deepest deep sleep, the brain waves are extremely synchronized, like in an orchestra, in which all instruments play precisely the same beat, without push-pull and with maximum strength. At this stage, good deep sleepers need the noise of a plane taking off to get them back out of Morpheus' arms. The conductor of this sleep orchestra sits in a certain area of ​​the brain that guides practically all players - that is, areas of the brain - through the nocturnal sleep symphony. The comparison with an orchestra is not so absurd, as many composers have already tried to transform the nocturnal vibration pattern of the brain waves into music. Anyone who deals with sleep for professional reasons is always fascinated by observing the brain wave pattern of a sleeping person: peaks, valleys and rapid peaks move in waves from the left to the right edge of the computer screen, like hieroglyphs from another world that is still not are deciphered. So we don't know why we sleep through four to six cycles per night, which always end with a phase in which our eyes move wildly under the closed lids, the so-called REM (rapid eye movement) phase. We also do not know why we dream and why our dreams, especially in the REM phase, can be emotionally and strongly bizarre colored. What we definitely know is that the different brain wave patterns during sleep are very beneficial for processing memory contents of previous days, consolidating what has been learned, strengthening the immune system, the growth of new cells and much more. Unless we are suddenly woken up by an alarm clock, the brain clock ensures that we do not sleep forever. About two to three hours before you actually wake up, the engine is started slowly: The melatonin production stops during sleep, the body temperature, the heart rate and the cortisol level rise continuously so that waking up is as easy as possible. It seems as if getting up is actively initiated hours before the expected sunrise. Incidentally, the Inuit avoid getting up suddenly in the morning, especially in the deepest polar winter when the nights seem eternal. According to the ethnologist Jean Malaurie, a good half an hour goes by in which everyone enjoys their indolence in their own way. You never get up suddenly, because the Inuit believe that the soul is removed during sleep and must return to the body when waking up. You should therefore never get up suddenly if you want to avoid disturbing this "swarm of souls". It remains to be seen whether this is related to the Inuit's very low risk of heart attack. In our part of the world, the risk of a heart attack is highest in the morning around the time you get up.

Basic need for recovery
Why do we have to sleep? The answer is simple and is called «relaxation». Whenever we get sick, have an injury, or want to recover from a stressful situation, we lie down and try to sleep. Brain injured people initially sleep a lot, and as they recover from the injury, so does their wakefulness. It seems like we sleep in order to be awake. There are people who can get by without food, but there is no one who can do without sleep. The world record is eleven days without sleep. Sleep is a basic need. The hunger for sleep is never lost, whereas the feeling of hunger when eating does not disappear after two to four days of fasting. Like the alternation of day and night, sleep is subject to a rhythmic sleep-wake sequence, which, interestingly, both tick in time; this is called "active spontaneous synchronization". Despite technical achievements such as the airplane and artificial light, which enable us to sleep and be awake at all times of the day, we find it difficult to work shifts or to cross multiple time zones. The dictates of the internal physiological clock are so strong that they cannot simply be reprogrammed using “modern” tools. Humans and other living beings are basically clocks that respond to different environmental influences with rhythmic sequences on different levels - from genes to behavior. One of the answers is sleep, which should definitely be respected and cared for so that we avoid overexploiting our own health. Incidentally, according to a study in the USA, the cost of accidents caused by lack of sleep was already $ 56 billion twenty years ago.