The Info List - Fatigue (medical)

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.[1][2][3] 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.[4] 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.[5]


1 Classification

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[edit] See also: Central nervous system fatigue

Physical fatigue[edit] Main article: Muscle
fatigue Physical fatigue, or muscle fatigue, is the temporary physical inability of a muscle to perform optimally. The onset of muscle fatigue during physical activity is gradual, and depends upon an individual's level of physical fitness, and also upon other factors, such as sleep deprivation and overall health. It can be reversed by rest.[6] Physical fatigue can be caused by a lack of energy in the muscle, by a decrease of the efficiency of the neuromuscular junction or by a reduction of the drive originating from the central nervous system.[7] The central component of fatigue is triggered by an increase of the level of serotonin in the central nervous system.[8] During motor activity, serotonin released in synapses that contact motoneurons promotes muscle contraction.[9] During high level of motor activity, the amount of serotonin released increases and a spillover occurs. Serotonin
binds to extrasynaptic receptors located on the axon initial segment of motoneurons with the result that nerve impulse initiation and thereby muscle contraction are inhibited.[10] Muscle
strength testing can be used to determine the presence of a neuromuscular disease, but cannot determine its cause. Additional testing, such as electromyography, can provide diagnostic information, but information gained from muscle strength testing alone is not enough to diagnose most neuromuscular disorders.[11] People with multiple sclerosis experience a form of overwhelming lassitude or tiredness that can occur at any time of the day, for any duration, and that does not necessarily recur in a recognizable pattern for any given patient, referred to as "neurological fatigue".[12][13] Mental fatigue[edit] Mental fatigue is a temporary inability to maintain optimal cognitive performance. The onset of mental fatigue during any cognitive activity is gradual, and depends upon an individual's cognitive ability, and also upon other factors, such as sleep deprivation and overall health. Mental fatigue has also been shown to decrease physical performance.[4] It can manifest as somnolence, lethargy, or directed attention fatigue. Decreased attention may also be described as a more or less decreased level of consciousness.[14] In any case, this can be dangerous when performing tasks that require constant concentration, such as operating large vehicles. For instance, a person who is sufficiently somnolent may experience microsleep. However, objective cognitive testing can be used to differentiate the neurocognitive deficits of brain disease from those attributable to tiredness.[citation needed] The perception of mental fatigue is believed to be modulated by the brain's reticular activating system (RAS).[citation needed]

Comparison with sleepiness[edit] Fatigue is generally considered a more long-term condition than sleepiness (somnolence).[15] Although sleepiness can be a symptom of medical issues, it usually results from lack of restful sleep, or a lack of stimulation.[16] 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.[17] 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[edit] 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[edit] 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.[18] 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
Chronic fatigue syndrome
(CFS)[19] Drug abuse
Drug abuse
including alcohol abuse[19] Depression and other mental disorders that feature depressed mood Eating disorders, which can produce fatigue due to inadequate nutrition Endocrine diseases like diabetes mellitus and hypothyroidism Fibromyalgia Gulf War syndrome Heart disease HIV Inborn errors of metabolism such as fructose malabsorption.[20][21] Infectious diseases
Infectious diseases
such as infectious mononucleosis. Irritable bowel syndrome Leukemia
or lymphoma Liver failure Lyme disease Neurological disorders such as narcolepsy, Parkinson's disease
Parkinson's disease
and post-concussion syndrome Physical trauma
Physical trauma
and other pain-causing conditions, such as arthritis Sleep
deprivation or sleep disorders Spring fever Stroke Thyroid diseases Uremia, which is caused by kidney disease

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[edit]

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 cases.[22] 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.[23] Other tests may be chosen depending on the patient's social history, such as an HIV
test or pregnancy test. Measurement[edit] Fatigue can be quantitatively measured. Devices to measure medical fatigue have been developed by Japanese companies, among them Nintendo.[24] Nevertheless such devices are not in common use outside Japan. See also[edit]

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. PMID 1561512.  ^ 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. PMID 9232549.  ^ 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. PMID 19131473.  ^ 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 2013.  ^ 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). " Serotonin
and central nervous system fatigue: nutritional considerations" (PDF). Am. J. Clin. Nutr. 72 (2 Suppl): 573S–8S. PMID 10919962.  ^ Perrier JF, Delgado-Lezama R (2005). "Synaptic release of serotonin induced by stimulation of the raphe nucleus promotes plateau potentials in spinal motoneurons of the adult turtle". J. Neurosci. 25 (35): 7993–9. doi:10.1523/JNEUROSCI.1957-05.2005. PMID 16135756.  ^ Cotel F, Exley R, Cragg SJ, Perrier JF (2013). " Serotonin
spillover onto the axon initial segment of motoneurons induces central fatigue by inhibiting action potential initiation". Proc Natl Acad Sci U S A. 110 (12): 4774–9. doi:10.1073/pnas.1216150110. PMC 3607056 . PMID 23487756.  ^ Enoka RM, Duchateau J (1 January 2008). " Muscle
fatigue: what, why and how it influences muscle function". The Journal of Physiology. 586 (1): 11–23. doi:10.1113/jphysiol.2007.139477. PMC 2375565 . PMID 17702815.  ^ Comi G, Leocani L, Rossi P, Colombo B (March 2001). "Physiopathology and treatment of fatigue in multiple sclerosis". J. Neurol. 248 (3): 174–9. doi:10.1007/s004150170222. PMID 11355149.  ^ Mills RJ, Young CA, Pallant JF, Tennant A (2010). "Development of a patient reported outcome scale for fatigue in multiple sclerosis: The Neurological Fatigue Index (NFI-MS)". Health Qual Life Outcomes. 8: 22. doi:10.1186/1477-7525-8-22. PMC 2834659 . PMID 20152031.  ^ Giannini, A.J. (1992). "Fatigue, Chronic". In Taylor, R.B. Difficult Diagnosis 2. Philadelphia: W.B. Saunders Co. p. 156. ISBN 0-7216-3481-8. OCLC 954530793.  ^ Shen J, Barbera J, Shapiro CM (2006). "Distinguishing sleepiness and fatigue: focus on definition and measurement". Sleep
Med Rev. 10 (1): 63–76. doi:10.1016/j.smrv.2005.05.004. PMID 16376590.  ^ Hoddes E, Zarcone V, Smythe H, Phillips R, Dement WC (1973). "Quantification of sleepiness: a new approach". Psychophysiology. 10 (4): 431–6. doi:10.1111/j.1469-8986.1973.tb00801.x. PMID 4719486.  ^ Mayou R (1999). "Chronic fatigue and its syndromes". BMJ. 318 (7176): 133A. doi:10.1136/bmj.318.7176.133a. PMC 1114599 . PMID 9880310.  ^ Fukuda K, Straus SE, Hickie I, Sharpe MC, Dobbins JG, Komaroff A (15 December 1994). "The chronic fatigue syndrome: a comprehensive approach to its definition and study. International Chronic Fatigue Syndrome Study Group". Ann Intern Med. 121 (12): 953–9. doi:10.7326/0003-4819-121-12-199412150-00009. PMID 7978722.  ^ a b Avellaneda Fernández A, Pérez Martín A, Izquierdo Martínez M, Arruti Bustillo M, Barbado Hernández FJ, de la Cruz Labrado J, Díaz-Delgado Peñas R, Gutiérrez Rivas E, Palacín Delgado C, Rivera Redondo J, Ramón Giménez JR (2009). "Chronic fatigue syndrome: aetiology, diagnosis and treatment". BMC Psychiatry. 9 Suppl 1: S1. doi:10.1186/1471-244X-9-S1-S1. PMC 2766938 . PMID 19857242.  ^ Whitehead WE, Palsson O, Jones KR (2002). "Systematic review of the comorbidity of irritable bowel syndrome with other disorders: What are the causes and implications?". Gastroenterology. 122 (4): 1140–1156. doi:10.1053/gast.2002.32392. PMID 11910364.  ^ Gibson PR, Newnham E, Barrett JS, Shepherd SJ, Muir JG (2006). "Review article: Fructose malabsorption
Fructose malabsorption
and the bigger picture". Alimentary Pharmacology & Therapeutics. 25 (4): 349–63. doi:10.1111/j.1365-2036.2006.03186.x. PMID 17217453.  ^ Nijrolder I, van der Windt D, de Vries H, van der Horst H (November 2009). "Diagnoses during follow-up of patients presenting with fatigue in primary care". CMAJ. 181 (10): 683–7. doi:10.1503/cmaj.090647. PMC 2774363 . PMID 19858240.  ^ EMedicine Health. "Fatigue Exams and tests" 2010-01-25. ^ "Nintendo's first health care device will be sleep and fatigue tracker". The Japan Times Online. Reuters. 30 October 2014. Retrieved 29 June 2017. 

Further reading[edit] 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.

External links[edit]

Wikimedia Commons has media related to Fatigue.

Fatigue — Information for Patients, U.S. National Cancer
Institute Information leaflet from mental health charity The Royal College of Psychiatrists Is exhaustion an actual medical diagnosis? from Slate.com

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Symptoms and signs: general / constitutional (R50–R61, 780.6–780.9)




of unknown origin Drug-induced fever Postoperative fever


e.g., Sleep
hyperhidrosis; "sweating"

Hyperpyrexia Hyperthermia


Chills Hypothermia


Headache Chronic pain Cancer
pain Myalgia

Malaise and fatigue


e.g., Muscular atrophy

Debility (or asthenia) Lassitude Lethargy Muscle
tremors Tenderness


Flu-like symptoms

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Common cold


Adenovirus Coronavirus Enterovirus Human metapneumovirus Human parainfluenza viruses Human respiratory syncytial virus Orthomyxoviruses

Influenza A virus Influenza B virus Influenza C virus



Cough Fatigue Fever Headache Loss of appetite Malaise Muscle
aches Nasal congestion Rhinorrhea Sneezing Sore throat Weakness


Acute bronchitis Bronchiolitis Croup Otitis media Pharyngitis Pneumonia Sinusitis Strep throat


Antiviral drugs Pleconaril

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Mental processes


Awareness Cognitive dissonance Comprehension Consciousness Imagination Intuition


Amodal Haptic (touch) Sound

pitch harmonics speech

Social Perception
as interpretation Visual Color

RGB model

Peripheral Depth Form


Encoding Storage Recall Consolidation


Attention Higher nervous activity Intention Learning Mental fatigue Mental set Thinking Volition

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