On average, we humans sleep between seven and eight hours every night – oversleeping about a third of our lives. Time that could be well used for other things, but without enough sleep we feel tired and battered. But why do we need to sleep at all? This is a question that has not yet been definitively answered – the only thing that is certain is that sleep has a vital function for us. But not only for us humans, but also for animals sleep is of high importance: because although it can become life-threatening for some animals, they lay down regularly to sleep.
Functions of sleep
Night after night, we humans go to bed and sleep – but why do we actually sleep? For a long time, it was assumed that sleep had no important function – it was seen as a dead-like rest and therefore popularly known as the ‘little brother of death’. Even today, the exact function of sleep has not been researched with certainty. However, it is now certain that sufficient sleep is indispensable for human development and health. In the past, sleeping at night was often explained by the fact that the body uses less energy during sleep. But in fact our body is more active at night than we think, which is why calorie consumption during sleep is hardly less than during the day. If you sleep for eight hours, you only save about as many calories as a glass of milk compared to when you are awake. Today, there are various assumptions about what function sleep has for us humans.
Experiences of the day are processed
Even if our body looks calm and relaxed on the outside when we sleep, there is a lot going on in our brain: the experiences of the day are evaluated there at night: Important information is sorted into already existing categories, while superfluous information is disposed of. This sorting work cannot take place while we are awake, because otherwise stimulus processing would be disturbed and hallucinations would occur. Only during sleep, when we are disconnected from the stimuli of the outside world, can we sort the data stream of the day in peace. The fact that the brain processes the previous day’s information overnight also benefits us in learning. During sleep, what we have learned during the day is anchored in our memory. The new information is sorted and stored overnight and is easier to recall the next day. We are particularly good at retaining content that we memorize shortly before falling asleep.
The immune system is strengthened
While we sleep, our immune system works at full speed: It releases at night namely particularly many immune-active substances. Who sleeps a lot strengthens his defenses, who sleeps too little is sick more often. In the long run, too little sleep can even lead to illnesses such as high blood pressure or gastrointestinal problems. Since our body can regenerate particularly well during sleep, it is no wonder that we sleep so much when we are sick: Our body ensures that we are put into a state in which the immune system can work particularly well.
Metabolism regulates itself during sleep
During sleep, metabolic products that have accumulated in the body during the day are broken down. If one sleeps too little, these cannot be completely broken down and the metabolism gets out of sync. This can increase the risk of developing lifestyle diseases such as diabetes or becoming overweight.
Growth hormones are released
During the night, our hormonal balance also works particularly hard: for example, we secrete the hormone leptin, which ensures that we do not feel hungry or thirsty during sleep. Only when we wake up does its counterpart, ghrelin, take control again and we get hungry. In addition, a particularly large amount of growth hormones are released at night, so children actually grow while they sleep. The growth hormones also ensure that wound healing proceeds particularly quickly during sleep. That is why damaged tissue regenerates faster overnight than during the day.
The psyche recovers during sleep
Not only the body comes to rest during sleep, but also the psyche can recover. That’s why people who frequently struggle with sleep disorders suffer from depression significantly more often than people who have a healthy sleep.
Lack of sleep: symptoms and consequences
People who sleep too little over a long period of time put their bodies at increased health risk.Thus, high blood pressure, diabetes and obesity can be caused by lack of sleep. Likewise, anxiety and depression can be among the consequences of sleep deprivation. Typical symptoms of sleep deprivation include the following.
- Fatigue and listlessness
- Low ability to concentrate
- Irritability
- Freezing and
- General malaise
Those who do not sleep for more than 24 hours at a time have severely impaired cognitive performance. It is roughly equivalent to an alcohol level of 0.85 per mille. Sleep deprivation of more than 48 hours can also cause hallucinations and memory lapses. In addition, a link between chronic sleep deprivation and early death is also suspected.