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Fatigue (also out of date defatigation ) is a physiological and psychological state of reduced alertness and lack of strength and drive. The signs of tiredness appear before sleep , under unfavorable sleep hygiene conditions and with certain health disorders, but also as daytime sleepiness . The fatigue that occurs after sexual intercourse, and especially after male orgasm , is known as post-coital fatigue .

Physiological fatigue arises from a qualitative or quantitative lack of sleep ( hyposomnia / insomnia ) and is perceived as an insurmountable, persistent feeling of exhaustion, accompanied by a reduced capacity for physical and mental activity.

General signs of tiredness

Signs of tiredness are reduced ability to concentrate and perform, and perception is impaired. Furthermore, one is listless, more easily irritable for things that would be more relaxed if one were not tired. A slight high can have disinhibiting effects that were not expected. Hypnagogia and general hallucinations can also occur, especially with long-term lack of sleep . Some people also complain of freezing when they are tired.

Daytime sleepiness

Daytime sleepiness is caused by too little sleep , short or long-term sleep deprivation, and sleep disorders . Chronic fatigue can also be a symptom of an illness . As a rule, tiredness can be compensated for by sleeping long enough. However, if the cause of the tiredness is a sleep disorder, one speaks of daytime sleepiness . With her, even enough sleep cannot noticeably reduce symptoms. Appropriate help can only be provided by a doctor through a more precise diagnosis. Fatigue is also a common side effect of medication .

Late risers and early risers

left: chronotypes (e.g. " 0-8 ": the person sleeps on average from midnight to 8 am) ;
right: lack of sleep on working days or on days off.

As can be seen from the gray, right-hand part of the graphic of the Center for Chronobiology at the Institute for Medical Psychology at LMU , the majority of the German population complains about a lack of sleep. Here, those having a sleep lack of working days indicate to those with sleep deprivation on days ( day of rest ) in the plurality. The gray graph shows the proportion of the population as a function of sleep deprivation.

The left, colored part of the graphic shows the distribution in the population as a function ( ) of the chronotypes , which approximately describes a bell curve ( normal distribution ). The colorful graphic shows that the left ascending leg of the normal distribution curve includes the early risers (“larks”), the area around the turning point of the curve includes the normal type and the right descending leg includes the late risers (“owls”). The left leg of the curve is shorter and climbs faster. The right thigh is overall longer and descends more moderately.

The Center for Chronobiology distinguishes between seven chronotypes:

  • purple: "extreme early type",
  • blue: "moderate early type",
  • light blue: "light early type",
  • green: "normal type",
  • yellow: "slight late type",
  • orange: "moderate late type" and
  • red: "extreme late type".

The normal type (light blue and green) make up the majority of the population. The late riser ("owl", "evening type", "evening person", "night person", "late rhythmic"; yellow, orange and red) occurs more frequently than the early riser ("lark"; purple and blue in the graphic). .


Persistent lack of sleep leads to chronic fatigue , which results in headaches, difficulty concentrating, burning eyes, heavy legs and increasing sensitivity to pain . Persistent sleep deprivation leads to more severe symptoms such as apathy, somnolence , depression, and cognitive disorders.

Excessive tiredness is often the cause of human errors such as traffic accidents , especially as a result of so-called microsleep .

Fatigue when performing special tasks

Sleeping nurse in protective gear during the April 2020 COVID-19 pandemic

People in numerous professions are at risk if they are tired or alert; especially shift workers and people who do night shifts or work in alternating shifts (see also Sunday work ).

Labor law and occupational medicine are responsible for avoiding dangers beyond personal responsibility . Employees in particularly endangered occupations receive collective or collective bargaining agreements or works agreements with regulations to compensate for the difficulties, and special vacation and pension regulations are negotiated in this regard. Thanks to the listing of all working hours and free time in the form of regular duty rosters based on medical principles, unnecessary exhaustion due to the organization is also avoided.

An Israeli study found that tired judges are more likely to rule against the defendant:

“It is already known from previous studies that people become mentally tired when they have to make many decisions in a row. They then tend to simplify the decisions that are still needed by simply accepting and leaving the existing state. Not only judges, but also members of other professional groups would have to rethink their decisions critically, the researchers write. Doctors, financial experts or employees in university admissions offices, for example, are likely to be influenced by their fatigue when making decisions. "

Warning systems and measurability of fatigue

Since the 1990s, researchers have been looking for ways to measure the drowsiness of drivers and drivers of other means of transport (e.g. trucks) in order to warn them in good time before falling asleep or increasing inattentiveness. On the other hand, there have been so-called dead man's facilities - for train drivers and subway drivers, for example . Further developments in the form of so-called driver assistance systems are now ready for the market and available. Fatigue is technically measurable both in the way a person reacts and in their voice.

Chronic fatigue as a symptom of illness

Permanent, i.e. chronic, fatigue can be a pathophysiological symptom of illness. Pathological fatigue is one of the symptoms of iron deficiency and vitamin D3 deficiency and is an accompanying symptom of many diseases that can occur with flu, rheumatism, heart attacks, diabetes, cancer, AIDS, Pfeiffer glandular fever and many other diseases. In a depression include continuous or intermittently occurring fatigue and listlessness of the main symptoms. As malaise and fatigue, it is also a symptom of a disorder .

In Germany in particular use oncologists and palliative care in case of permanent fatigue as part of a cancer the term fatigue . In the English-speaking world, on the other hand, the term fatigue describes any persistent tiredness, regardless of the cause.

See also


Web links

Commons : Fatigue  - Collection of pictures, videos and audio files
Wiktionary: Fatigue  - explanations of meanings, word origins, synonyms, translations
Wikiquote: Fatigue  - Quotes

Individual evidence

  1. a b graphic: "Frequency of different chronotypes in the (German) population", LMU Institute for Medical Psychology, Center for Chronobiology , 2010. Left graphic: Frequency of the different sleep times (e.g. "0 - 8" means the person is sleeping on average from midnight to 8 a.m.); Right graphic: lack of sleep or excess sleep on working days compared to days off.
  2. light blue: "light early type", green: "normal type"
  3. yellow: "slight late type", orange: "moderate late type", red: "extreme late type"
  4. purple: "extreme early type", blue: "moderate early type"
  5. Tired judges decide against the accused . Spiegel Online , April 12, 2010
  6. German Transport Council: Fatigue in Road Traffic ( Memento of the original from August 18, 2017 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / www.dvr.de
  7. "What the voice reveals about us"
  8. ^ What Causes Prolonged Fatigue after Infectious Mononucleosis. Retrieved May 14, 2020 .
  9. Fatigue Symptoms, Causes, and Treatment. Retrieved May 13, 2020 .