Why we need sleep

We sleep through about a third of our lives. But why do we sleep at all? It's simple: Many physical processes only take place during sleep. For example, the body has a stronger immune defense at night.

"It is clear that sleep, as we subjectively experience it, serves the purpose of recovery," says sleep researcher Prof. Dr. Dieter Riemann. This is possibly related above all to the amount of deep sleep an organism gets during the night.

Refuel the immune system while you sleep

Metabolism and circulation behave differently during sleep than when awake. This is important for health, because the body has a stronger defense against viral and bacterial infections during sleep. Conversely, if the deep sleep phase is suppressed, this can significantly impair the immune system's ability to function. "Findings from experimental research show that it is precisely during the deep sleep phase that important processes take place that regulate the immune system," says Prof. Dr. Riemann.

The phases of sleep

Sleep is not a steady state. After falling asleep, sleep becomes increasingly deeper: from the waking state, one slips into so-called NONREM sleep. This is divided into four stages depending on the depth of sleep.

From the light, superficial sleep of stages 1 and 2, one glides swiftly into the deep sleep of stages 3 and 4. This deep sleep is important for the regeneration of the entire body, especially the brain.

After a while, sleep becomes lighter, and after about 90 minutes, the fifth sleep phase, known as the rapid eye movement (REM) phase, sets in. As the name suggests, in this phase the eyes move very quickly and the brain is just as active as when awake. In the REM phase, people dream particularly vividly and process the impressions of the day in these dreams. The REM phase thus serves more for mental recovery.

Need tips on how to sleep properly or want to learn more about sleep stages and sleep cycles? Then read the full article:

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