Sleep is a natural and self-evident part of life, just like breathing, eating or drinking. People spend around a third of their lives asleep. A good reason to take a closer look at sleep.

Research into sleep is a young discipline in medicine and only began in the early 1950s. There is now a great deal of well-founded knowledge about sleep, its importance and its complexity. However, there are also many myths, wisdoms and rumors surrounding sleep and its role in the health of the body and mind. Some are true, some are false, but one thing is certain: sleep is a mainstay of mental and physical well-being.

Sleep is an absolutely essential process for the general regeneration of the body. We realize how important it is when we have slept well and sufficiently. We feel well rested, the day starts more easily, we are in a better mood and our quality of life improves. Regular and sufficient sleep makes us mentally and physically more efficient, more balanced and we fall ill less often. Persistent sleep deprivation, on the other hand, causes serious mental and physical problems. It can seriously endanger our health. It is not just leaden tiredness and low resilience that follow a lack of sleep. Mental and physical performance decreases, especially concentration and alertness. The tendency to make mistakes, wrong decisions, irritability and the feeling of being overwhelmed increases. Many accidents and mishaps are the result of mistakes made by overtired people. One example is the notorious "microsleep" at the wheel of a vehicle.

During sleep, the immune system and the entire metabolism are given the opportunity for important regeneration and necessary "clean-up work". During sleep, which seems like a simple time of rest, the entire organism is working at full speed. International studies have shown that the cardiovascular system is relieved during sleep and that the immune system works particularly effectively. The brain in particular is more active in certain phases of sleep than when awake. Sleep research assumes that during sleep, the information of the day and also what has been learned is processed, filtered, organized and stored in long-term memory. Deep sleep plays a decisive role here.

The 5 phases of sleep

Sleep is a complex process and not a simple state of rest. Healthy, restful sleep goes through undisturbed cycles with 5 different sleep phases. The phases take place in a fixed rhythm, which can be represented by brain activity in the EEG (electroencephalogram). Sleeping through these cycles undisturbed determines whether sleep is restful or not.

Sleep research distinguishes between 5 sleep phases:

• Phase 1: Falling asleep phase (approx. 5% of sleep time), yellow
• Phase 2: light sleep phase (approx. 50% of sleep time), yellow
• Phases 3 and 4: Deep sleep phases (approx. 20% of sleep time), green
• Phase 5: Dream sleep phase or REM phase (approx. 25% of sleep time), red

• Phase 1 - Falling asleep phase
  In the first few minutes of falling asleep, the body becomes calm and relaxed. Breathing and the heartbeat slow down. Sleep is very superficial and can be interrupted by minor disturbances.

• Phase 2 - light sleep phase
  Sleep deepens, the muscles relax, consciousness fades out. Breathing and pulse increasingly slow down.

• Phases 3 and 4 - deep sleep phase
  Sleep is particularly deep and deep, and people are often very difficult to awaken at this stage. The deep sleep phase is the most important phase of sleep for mental and physical recovery.

• Phase 5 - Dream sleep phase / REM phase
  The deep sleep phase is quickly followed by the dream or REM phase. In this sleep phase, the skeletal muscles of the body are without tension. This prevents spontaneous movements during dreams. Blood pressure, pulse rate and breathing rate increase and the eyes move rapidly back and forth with the eyelids closed (REM = Rapid Eye Movement).

Each cycle with the 5 sleep phases lasts around 90 minutes and is repeated 4 to 6 times per night. Deep sleep dominates at the beginning of the night, with REM phases becoming more frequent towards the end. Surprisingly, we wake up around 30 times during the night without remembering it and without being disturbed in our sleep.

Is there a "recipe" for healthy sleep?

A suitable sleep rhythm:

• Sleep doctors recommend regular sleeping times as the basis for healthy sleep. In addition to the duration of sleep, this also includes regular times for going to bed and getting up. On average, Central Europeans sleep around 7 hours a night. However, individual sleep requirements can vary considerably from this average. Anyone who is tired and unrested in the morning after regularly sleeping for more than 7 hours may be a long sleeper with an increased need for sleep. Short sleepers feel rested and productive even after a short sleep of 4 to 7 hours. The individual need for sleep can be found by trial and error. The prerequisite is that there are no general sleep problems or sleep disorders.
• In addition to sleep quality and duration, bedtime is an important individual factor for a good night's sleep. Everyone knows the two sleep types: the "larks" and the "owls". The lark sleep type wakes up early in the morning and is most productive in the mornings. The owl, on the other hand, only has its peak of energy in the afternoon and remains productive until late at night. Once you have found out which sleep type you are, you should adjust your daily rhythm accordingly if possible.
• Long-distance travel, shift work or unstructured day-night habits can severely disrupt your sleep rhythm and make you ill for a long time. The owl sleep type has fewer adjustment problems than the lark and is also better equipped for night work. The internal clock sets the schedule and cannot be changed. Adaptation problems are therefore difficult to solve. Every tip boils down to a temporal adjustment of the sleep rhythm while taking your own sleep type into account.
• A sleep deficit cannot be avoided by "sleeping in" or compensated for by "sleeping in longer". The body automatically compensates for the lack of sleep through extended, increased deep sleep.
• The total duration of sleep is almost constant over the years. Even people over the age of 70 generally sleep for a similar length of time as in previous decades. The individuality of the need for sleep remains the same. The sleep rhythm changes with age and the amount of sleep at night decreases slightly. The body compensates for this with a midday nap.
  
  

A suitable sleeping environment:

The term "sleep hygiene" is used by sleep physicians to describe the measures that provide an optimal sleeping environment and other behaviors for deep, healthy sleep.

• An optimally designed bedroom is dark, quiet and cool. Darkness and silence have a calming effect and promote sleep, whereas noise and light disturb it and shorten the duration of sleep.
• Sleep researchers recommend a room temperature of around 16 to 18 degrees. This ensures that you do not suffer from hypothermia. It is important not to sweat or freeze. Individual temperature sensations may differ from this recommendation. Before going to bed, a five-minute burst of airing can provide fresh air in the bedroom. If possible, sleep with the window tilted, but without draughts.
• Every night, an adult loses around half a liter of fluid through breathing and the skin. Dry (heated) air dries out the airways and disturbs sleep. During the heating period, a humidifier can raise the humidity in the bedroom to a healthy 40 to 45 percent.
• The bed is an important purchase that should be thought through and tried out a little. The bed frame and slatted frame should be stable enough to withstand the body turning during sleep. The mattress and pillow should be selected according to individual needs. Both should support the body/head without sinking in too deeply. They should be comfortable and offer a pleasant lying position. The rule here is: the proof of the pudding is in the eating. Subjective feeling is the best guide.

Some behavior before going to bed can influence the quality of your night's sleep.

• Switch to a "rest mode" before going to bed. Exciting activities such as sport, a stimulating computer game or exciting movies activate the body and prevent the rest needed to fall asleep. As a result, falling asleep can be delayed despite being very tired and the entire night's rest can be impaired.
• A sumptuous meal, caffeine, nicotine or alcohol before falling asleep influence the sleep phases. Sleeping through the night is prevented by stimulating substances as well as by stimulated digestion.
• As tempting as a midday nap is, a 10-minute "power nap" is much more helpful for a good night's sleep with a normal sleep rhythm.
• Daily exercise in the fresh air, e.g. a walk during your lunch break, helps you to get tired in the evening and promotes healthy sleep.
• Sleep is permanently impaired if recurring disturbances interrupt the sleep phases. Sleep research has shown the consequences of sleep deficits caused by external influences, for example in parents with infants and small children, waking up due to night-time urination, pronounced snoring or sleep apnoea (breathing stops during sleep) or work-related (emergency and on-call services). In such cases, it is important to compensate or to avoid or treat the disturbances as far as possible.