On average, we humans sleep between seven and eight hours every night – and thereby sleep about a third of our lives. Time that could be used well for other things, but without enough sleep we feel tired and battered. But why do we have to sleep at all? A question that has not yet been finally clarified – it is only clear that sleep has a vital function for us. But sleep is of great importance not only for us humans, but also for animals: even though it can be life-threatening for some animals, they go to sleep regularly.
Functions of sleep
Every evening we go to bed and sleep – but why do we sleep anyway? For a long time it was assumed that sleep did not have an important function – it was considered dead-like rest and therefore popularly referred to as the ‘little brother of death’. The exact function of sleep has not been researched yet. However, it is now established that enough sleep is essential for human development and health.
In the past, nocturnal sleep was often explained by the fact that the body consumes less energy during sleep. But actually, our body is more active at night than you think, so the calorie consumption during sleep is hardly less than during the day. Who sleeps eight hours, saves compared to the waking state only about as many calories as a glass of milk .
Today, there are various assumptions about what sleep does for us humans.
Experiences of the day are processed
Even though our body looks outwardly calm and relaxed during sleep, there is a lot going on in our brains: there, at night, the experiences of the day are analyzed: Important information is classified into already existing categories, but superfluous ones are disposed of. This sorting work can not take place while awake, otherwise the stimulus processing would be disturbed and hallucinations would occur. Only in sleep, when we are disconnected from the stimuli of the outside world, we can sort the data stream of the day in peace.
The fact that the brain processes overnight the information from the previous day also benefits us when learning. Because during sleep, something learned is anchored in memory over the course of a day. The new information is sorted and stored overnight and is easier to access the next day. Especially good you can keep content, which is memorized shortly before falling asleep .
The immune system is strengthened
While we sleep, our immune system is working at full speed: it spills out at night namely a lot of immuno-active substances. If you sleep a lot, it strengthens your body’s defenses, but those who sleep too little are often sick. In the long run, too little sleep can even cause illnesses such as high blood pressure or gastrointestinal discomfort . Since our body can regenerate very well during sleep, it is no wonder that we sleep so much when we are ill: Our body ensures that we are put into a state where the immune system can work especially well.
During sleep, the metabolites that have accumulated in the body over the day are broken down. If one sleeps too little, they can not be completely broken down and the metabolism gets out of step. This can increase the risk of developing lifestyle diseases such as diabetes or being overweight.
Growth hormones are released
During the night, our hormone balance works particularly hard: For example, we release the hormone leptin , which ensures that we do not feel hungry or thirsty in our sleep. Only when we wake up does his opponent, the ghrelin, regain control and we get hungry. In addition, especially at night, many growth hormones are released, so children actually grow in their sleep. The growth hormones also ensure that wound healing progresses very quickly during sleep. Because of this, damaged tissue regenerates faster overnight than during the day.
The psyche recovers in sleep
Not only the body comes to rest in sleep, but also the psyche can recover. Because of this, people who often struggle with sleep disorders are significantly more likely to suffer from depression than people who have a sound sleep.
Lack of sleep: symptoms and consequences
Those who sleep too little for a longer period expose their bodies to an increased health risk. Thus, hypertension, diabetes and obesity can be caused by lack of sleep. Likewise, anxiety and depression may be among the consequences of lack of sleep.
The typical symptoms of lack of sleep include, among others
- Tiredness and listlessness
- low concentration ability
- Freeze and
- general malaise
Those who do not sleep for 24 hours at a time have a very limited cognitive performance. It corresponds approximately to an alcohol level of 0.85 per thousand. With sleep deprivation of more than 48 hours, it can also lead to hallucinations and memory lapses. In addition, a connection between chronic sleep deprivation and early death is suspected