According to chronobiology, day people or so-called larks are genetically day-active early risers. Night people or so-called owls, on the other hand, are nocturnal and sleep longer in the morning. Those who live contrary to their biologically pre-programmed sleep-wake rhythm in the long term can develop daytime fatigue and even psychoses.
What are day and night people?
In relation to humans, chronobiology distinguishes between so-called day people and night people in connection with the sleep-wake rhythm. Chronobiology deals with the temporal organization of behavioral patterns and physiological processes. In the context of this, the biological subfield describes, among other things, the sleep-wake rhythm of various living beings. This rhythm is genetically pre-programmed and can only be changed with difficulty without causing complaints. A certain adaptability is given, but the basic tendency cannot be changed. In relation to humans, chronobiology distinguishes between so-called day people and night people in connection with the sleep-wake rhythm. Day people are also known as larks. Night people are often called owls. Chronobiology understands these owls to be long sleepers who are more active during the night than during the day. Larks, on the other hand, are early risers and thus day people. Which activity tendency a person has depends on his or her genetics. The personal internal clock provides information about the affiliation to one of the groups. However, modern man no longer bases his rhythm on his inner clock, but on timepieces. Therefore, people often live contrary to their actual sleep-wake rhythm. This behavior can promote diseases and states of exhaustion.
Function and task
The sleep-wake rhythm of a living being is adapted to its living conditions. For example, lions are genetically active during twilight. They rest under the hot midday sun of their habitat. During the day, they sleep and regenerate. Only in the cool twilight phases do they really wake up and set out to hunt. Nocturnal rodents, on the other hand, escape daylight by limiting their foraging to the night hours. During these night hours, they are harder for many predators to detect. The sleep-wake rhythm is thus an important evolutionary parameter, and the sleep phases of an organism are controlled by its genetic sleep-wake rhythm. This is also true for humans. During sleep, we pass through the phases of light and deep sleep several times. In addition, there are the phases of REM sleep, i.e. dream sleep. The rhythm of the sleep phases matches the sleep-wake rhythm. Towards the end of sleep, the sleep phases alternate more and more rapidly until the person awakens. If a person belongs to the larks, then the accelerated alternation of sleep phases is on the early morning hours. For owls, on the other hand, the rapid alternation does not take place in the early morning hours, but is time-delayed with respect to them and comparatively later in the day. Those who sleep contrary to their biological rhythm thus get in the way of the natural regulation of their own sleep phases. As soon as the wake-up times do not coincide with the genetically predetermined waking phases, waking up disturbs the body in certain phases of sleep. The individual sleep phases are intended for relaxation, processing and physical regeneration. For example, the body’s self-healing powers are incomparably higher during sleep than during the waking phases. Defective cells are rejected during the sleep phases and replaced by processes of cell division. The individual sleep phases are coordinated with this goal of regeneration. A disturbance of the phases thus also disturbs the regeneration processes of the organism in the worst case or interrupts mental processing and learning processes, as they take place in the REM phase. The fact that humans orient their sleep according to external timers can disrupt this natural process if necessary and confuse the sleep phases. Day people behaving like night people or night people living like day people thus disturb their own sleep phases and regeneration processes, as is partly the case in shift work in modern times. The deviation from the genetically predetermined rhythm can result in various physical complaints.
Diseases and ailments
An indication of a disturbed sleep-wake rhythm or living contrary to one’s own sleep-wake rhythm can be frequent waking phases that interrupt sleep. In a sleep laboratory, such phenomena can be traced and assessed. Basically, people enter the individual sleep phases in certain proportions during each sleep. If the given ratio of these sleep phase proportions is disturbed, then this can also be an indication of living contrary to one’s own rhythm. The proportions of the sleep phases can also be checked during an examination in a sleep laboratory and estimated on the basis of brain wave measurements. Those who do not live according to their inner clock have to struggle with various complaints as a consequence. First of all, a disturbed sleep-wake rhythm usually makes itself felt in the form of fatigue, tiredness or exhaustion. Those affected are often more susceptible to infections because their immune system can no longer regenerate extensively during the disturbed sleep phases. Concentration problems are just as common, for example because learning processes can no longer be processed during disturbed REM sleep. Since a disturbance of the sleep phases also impedes processes of mental processing, psychological complaints may also occur later. For example, a permanently disturbed sleep-wake rhythm can manifest itself in depression. If a chronic disorder is present, then sometimes even psychoses develop from the depressions.
