Sleep and waking follow a natural rhythm. At nighttime we go through different phases. The organism reacts very sensitively to irregularities
Awake during the day, sleep well at night: that’s the natural rhythm
It can not be done without sleep
Even if there are people who are trying to prove the opposite in all sorts of experiments: At some point, their eyes also fall to them. It can not be done without sleep. No wonder then that the list of physical and psychological consequences of lack of sleep is quite long.
Sleep deprivation is not only a reaction of people with decreasing concentration and reduced mental capacity; they become increasingly irritable, moody and have a feeling of deception , including personality disorders and thoughts of suicide. Muscle tension, respiration, heart rate, blood pressure, body temperature, hormones, metabolism and other functions get mixed up when the natural rhythm of sleeping and waking is disturbed in the long term.
The normal sleep rhythm follows the change of day and night
Most of the processes in the body adapt to the change of day and night (circadian rhythm over 24 hours) and enable us to wake up in the morning and tired in the evening . An important role is played by certain groups of nerve cells in the brain, which have connections to the optic nerves and also to other areas of the brain. Day and night, light and dark so directly influence the sleep-wake cycle.
The coordinated nerve signals regulate the up and down of hormones , the body temperature and certain chemical substances that are also involved in the immune system. At night, for example, the hormone melatonin and growth hormones are released, which promote sleep. They decrease in the morning when the hormone cortisol rises again, which makes us feel better.
Then the body temperature also increases. It drops again in the evening so we can sleep better. Incidentally, the body temperature also has a short-term low during the day, in the early afternoon hours. At the same time, many people feel tired just at this time, and those who like and can, then have a short midday rest.
Two basic stages break down sleep: REM and NREM
Sleep is characterized by two basic stages in which the central nervous system and various body functions are respectively active and less active, allowing recovery and regeneration during sleep.
- In one of these sleep stages, the sleeper quickly swivels his eyes under his closed eyelids. Physicians therefore speak of REM sleep (English rapid eye movement ). At this stage we dream particularly vividly. That’s why the dream sleep was mentioned earlier. About 20 percent of its bedtime is spent by adults in REM sleep, compared to about half of those in infancy.
- The other stage is NREM ( non rapid eye movement ) sleep , which is divided into four phases: two light sleep phases and two deep sleep phases. These phases replace each other several times during the night with REM sleep, while in the morning REM sleep and light sleep phases predominate (see graph above).
Therefore, whoever does not come to rest at night is our brain . However, it redirects its activities and uses the bedtime for important cleanup and repair work. Scientists are still on the track for more precise procedures. Nerve cells, which were heavily used during the day and are subject to many influences, can shut down and regenerate in the opinion of experts in their sleep.
The confusion and illusions, which often occur after prolonged sleep deprivation, may be explained by the fact that the nervous system is constantly overloaded when it has no chance to get rid of superfluous ballast and to sort things out in peace. In other areas, new connections are created at night between the nerve cells. Newly learned things are so consolidated and anchored in the memory . Who sleeps well, learns easier and more sustainable.
Each phase is important for the recovery function of sleep. Essential body processes such as blood pressure, digestive activity or muscle tension also change at night, depending on what stage the sleeper is in. The blood pressure, for example, drops during deep sleep. If the sleep is interrupted several times, the non-dormouse even has to get up, for example, the blood pressure also rises again. For example, prolonged sleep problems can, among other things, promote hypertension .
The different sleep stages are controlled by finely tuned nerve signals in the brain. Anything that affects or alters this interaction also disturbs the natural sleep rhythm.
For example, stimulants such as coffee, nicotine or alcohol as well as certain medications can influence REM sleep as well as deep sleep. This also applies to diseases that affect heart and respiratory activity, nerves, muscles or metabolism.
An essential role plays the psyche . When thoughts are centered around worries, fears , unresolved issues, pressures and conflicts, stress hormones continue to be released, leaving the entire organism unable to calm down. For sleep architecture, as experts note the course of the different phases, hormones are important as serotonin and norepinephrine, which are in imbalance in depression . Sleep disorders, especially early morning waking, may therefore indicate depression.
Five or ten hours – how much sleep do we need?
Regardless of the eternal discussions between long and short sleepers , early risers and nocturnal people: the amount of sleep and sleeping hours are within a certain range, but they vary from person to person. Predisposition, age and habits play a role here.
Ultimately, the decisive factor is how well a person feels in the morning , whether he is tired and unfocused during the day, or whether he spends most of the day full of energy and mentally and physically, apart from natural lows. For some, this is the case after six hours of sleep, others only after nine hours. People who tend to sleep shorter often often use a short nap during the day ( power napping ). However, such a microsleep can not compensate for a permanent lack of sleep or a bad night’s sleep.
Most effective: About seven to eight hours of sleep
Scientific studies indicate that a good average of seven to eight hours of sleep is most effective. For example, in studies of sleep and obesity, people who slept less than six hours a night gained weight faster than normal sleepers at seven to eight hours. However, those who stayed in bed for nine hours and longer also gained more pounds. Other tests concerning sleep duration and life expectancy also suggest that an average measure is the best fountain of youth.
Teenagers usually need more sleep than adults. They are also more common to the long-sleepers. After puberty, they then find their personal standard. In old age, this is reversed by many. Here the early risers predominate. However, the amount of sleep remains mostly unchanged, but it is spread over day and night, as older people take a nap more often during the day. In addition, the sleep becomes more superficial, the deep sleep phases decrease.
The trend in our society is more towards less sleep, as many feel that they can no longer afford or want to sleep. Lack of sleep and sleep disorders often cause serious health and everyday problems. For example, many traffic accidents occur because the driver is over-tired and thus less concentrated or therefore falls into a microsleep.
It is worthwhile in many ways to get to the bottom of the sleepers and then to do something about the restless or too short nights.