Why are we sleeping?

On average, we humans sleep between seven and eight hours every night – and thus oversleep about a third of our lives. Time that could be used for other things, but without enough sleep we feel  tired  and drained. But why do we need to sleep at all? A question that has not yet been finally clarified – the only thing that is certain is that sleep has a vital function for us. But sleep is not only of great importance for us humans, but also for animals: Because although it can be life-threatening for some animals, they go to sleep regularly.

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 regarded as a death-like rest and was therefore popularly referred to as ‘death’s little brother’. The exact function of sleep has not yet been researched with certainty. However, it is now clear that sufficient sleep is essential 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 you think, which is why the  calorie consumption  during sleep is hardly lower than during the day. Sleeping eight hours only saves about as many calories as a glass of  milk compared to being awake  .

Today there are various assumptions about the function of sleep 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: At night, the experiences of the day are evaluated there: Important information is classified into existing categories, while superfluous information is discarded. This sorting work cannot take place in the waking state, since otherwise the stimulus processing would be disturbed and hallucinations would occur. Only when we are asleep, when we are disconnected from the stimuli of the outside world, can we sort through the day’s data stream in peace.

The fact that the brain processes the information from the previous day overnight also benefits us when learning. When you sleep, what you have learned during the day is anchored in your memory. The new information is organized and stored overnight and is more readily available the next day. It is particularly good to retain content that you memorize just before you  fall asleep  .

The immune system is strengthened

While we sleep, our  immune system works  at full speed: it releases a particularly large number of immune-active substances at night. Those who sleep a lot strengthen their  immune system, while those who sleep too little are more likely to get sick. In the long run, too little sleep can even lead to diseases 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.

The metabolism regulates itself during sleep

During sleep, the metabolic products that have accumulated in the body during the day are broken down. If you sleep too little, these cannot be broken down completely and  your metabolism  gets out of step. This can increase the risk of developing lifestyle diseases such as  diabetes  or becoming overweight.

Growth hormones are released

Our hormone balance also works particularly hard during the night: For example, we release the hormone  leptin  , which ensures that we do not feel hungry or thirsty while we sleep. Only when we wake up does its opponent, the ghrelin, take control again and we get hungry. In addition, a particularly large number of growth hormones are released at night, so children actually grow while they sleep. The growth hormones also ensure that wound healing progresses 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 is why people who often struggle with insomnia suffer significantly more often from  depression  than people who have a healthy sleep.

Lack of sleep: symptoms and consequences

Those who sleep too little over a longer period of time expose their bodies to an increased health risk. High blood pressure, diabetes and obesity can be caused by lack of sleep. Anxiety and depression can also be a consequence of lack of sleep.

Typical symptoms of lack of sleep include:

• tiredness and listlessness
• low ability to concentrate
• irritability
• freezing and
• general malaise

Anyone who does not sleep for more than 24 hours at a time has severely limited cognitive performance. It roughly corresponds to an alcohol level of 0.85 per mille. Sleep deprivation for more than 48 hours can also cause hallucinations and memory lapses. In addition, a connection between chronic lack of sleep and early death is suspected.