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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