Fatigue is a subjective feeling of tiredness which is distinct from weakness, and has a gradual onset. Unlike weakness, fatigue can be alleviated by periods of rest. Fatigue can have physical or mental causes. Physical fatigue is the transient inability of a muscle to maintain optimal physical performance, and is made more severe by intense physical exercise. Mental fatigue is a transient decrease in maximal cognitive performance resulting from prolonged periods of cognitive activity. It can manifest as somnolence, lethargy, or directed attention fatigue. Medically, fatigue is a non-specific symptom, which means that it has many possible causes and accompanies many different conditions. Fatigue is considered a symptom, rather than a sign, because it is a subjective feeling reported by the patient, rather than an objective one that can be observed by others. Fatigue and 'feelings of fatigue' are often confused.
1.1 Physical fatigue 1.2 Mental fatigue
2 Comparison with sleepiness 3 Causes
3.1 Chronic fatigue
4 Diagnosis 5 Measurement 6 See also 7 References 8 Further reading 9 External links
Classification See also: Central nervous system fatigue
Comparison with sleepiness Fatigue is generally considered a more long-term condition than sleepiness (somnolence). Although sleepiness can be a symptom of medical issues, it usually results from lack of restful sleep, or a lack of stimulation. Chronic fatigue, on the other hand, is a symptom of a greater medical problem in most cases. It manifests in mental or physical weariness and inability to complete tasks at normal performance. Both are often used interchangeably and even categorized under the description of 'being tired.' Oftentimes fatigue is described as an uncomfortable tiredness, whereas sleepiness is comfortable and inviting. Causes Fatigue is a normal result of working, mental stress, overstimulation and understimulation, jet lag or active recreation, depression, boredom, disease and lack of sleep. It may also have chemical causes, such as poisoning, low blood sugar, or mineral or vitamin deficiencies. Chronic blood loss frequently results in fatigue, as do other conditions that cause anemia. Fatigue is different from drowsiness, where a patient feels that sleep is required. Fatigue is a normal response to physical exertion or stress, but can also be a sign of a physical disorder. Temporary fatigue is likely to be a minor illness like the common cold as one part of the sickness behavior response that happens when the immune system fights an infection. Chronic fatigue Prolonged fatigue is a self-reported, persistent (constant) fatigue lasting at least one month. Chronic fatigue is a self-reported fatigue lasting at least six consecutive months. Chronic fatigue may be either persistent or relapsing. Chronic fatigue is a symptom of many diseases and conditions. Some major categories of diseases that feature fatigue include:
Autoimmune diseases such as celiac disease, lupus, multiple sclerosis,
myasthenia gravis, Sjögren's syndrome, and spondyloarthropathy
Blood disorders such as anemia and hemochromatosis
Cancer, in which case it is called cancer fatigue
Chronic fatigue syndrome
Fatigue may also be a side effect of certain medications (e.g., lithium salts, ciprofloxacin); beta blockers, which can induce exercise intolerance; and many cancer treatments, particularly chemotherapy and radiotherapy. Diagnosis
Minor dark circles, in addition to a hint of eye bags, a combination which is suggestive of sleep deprivation.
One study concluded about 50% of people who have fatigue receive a
diagnosis that could explain the fatigue after a year with the
condition. In those people who have a possible diagnosis,
musculoskeletal (19.4%) and psychological problems (16.5%) are the
most common. Definitive physical conditions were only found in 8.2% of
If a person with fatigue decides to seek medical advice, the overall
goal is to identify and rule out any treatable conditions. This is
done by considering the person's medical history, any other symptoms
that are present, and evaluating of the qualities of the fatigue
itself. The affected person may be able to identify patterns to the
fatigue, such as being more tired at certain times of day, whether
fatigue increases throughout the day, and whether fatigue is reduced
after taking a nap.
Because disrupted sleep is a significant contributor to fatigue, a
diagnostic evaluation considers the quality of sleep, the emotional
state of the person, sleep pattern, and stress level. The amount of
sleep, the hours that are set aside for sleep, and the number of times
that a person awakens during the night are important. A sleep study
may be ordered to rule out a sleep disorder.
Depression and other psychological conditions can produce fatigue, so
people who report fatigue are routinely screened for these conditions,
along with drug abuse, poor diet, and lack of physical exercise, which
paradoxically increases fatigue.
Basic medical tests may be performed to rule out common causes of
fatigue. These include blood tests to check for infection or anaemia,
a urinalysis to look for signs of liver disease or diabetes mellitus,
and other tests to check for kidney and liver function, such as a
comprehensive metabolic panel. Other tests may be chosen depending
on the patient's social history, such as an
Cancer-related fatigue Combat stress reaction Fatigue (safety) Gaucher's disease Heat illness Malaise Microsleep Presenteeism Sleep-deprived driving
^ Gandevia SC (1992). "Some central and peripheral factors affecting
human motoneuronal output in neuromuscular fatigue". Sports Medicine.
13 (2): 93–8. doi:10.2165/00007256-199213020-00004.
^ Hagberg M (1981). "Muscular endurance and surface electromyogram in
isometric and dynamic exercise". Journal of Applied Physiology. 51
(1): 1–7. PMID 7263402.
^ Hawley JA, Reilly T (1997). "Fatigue revisited". Journal of sports
sciences. 15 (3): 245–6. doi:10.1080/026404197367245.
^ a b Marcora SM, Staiano W, Manning V (January 2009). "Mental fatigue
impairs physical performance in humans". Journal of Applied
Physiology. 106 (3): 857–864. doi:10.1152/japplphysiol.91324.2008.
^ Berrios GE (1990). "Feelings of fatigue and psychopathology: a
conceptual history". Compr Psychiatry. 31 (2): 140–51.
doi:10.1016/0010-440X(90)90018-N. PMID 2178863.
Weakness and fatigue". Healthwise Inc. Retrieved 2 January
^ Gandevia SC (2001). "Spinal and supraspinal factors in human muscle
fatigue". Physiol. Rev. 81 (4): 1725–89. PMID 11581501.
^ Davis JM, Alderson NL, Welsh RS (2000). "
Further reading Byung-Chul Han: Müdigkeitsgesellschaft. Matthes & Seitz, Berlin 2010, ISBN 978-3-88221-616-5. (Philosophical essay about fatigue as a sociological problem and symptom).
Danish edition: Træthedssamfundet. Møller, 2012, ISBN 9788799404377. Dutch edition: De vermoeide samenleving. van gennep, 2012, ISBN 9789461640710. Italian editions : La società della stanchezza. nottetempo, 2012, ISBN 978-88-7452-345-0. Korean edition: 한병철 지음 김태환 옮김. Moonji, 2011, ISBN 9788932023960. Spanish edition: La sociedad del cansancio. Herder Editorial, 2012, ISBN 978-84-254-2868-5.
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