Fatigue: Difference between revisions

Fatigue (in the general usage sense of normal tiredness) often follows prolonged physical or mental activity. Physical fatigue results from [[muscle fatigue]] brought about by intense [[physical activity]].<ref>{{cite journal | vauthors = Gandevia SC | title = Some central and peripheral factors affecting human motoneuronal output in neuromuscular fatigue | journal = Sports Medicine | volume = 13 | issue = 2 | pages = 93–98 | date = February 1992 | pmid = 1561512 | doi = 10.2165/00007256-199213020-00004 | s2cid = 20473830 }}</ref><ref>{{cite journal | vauthors = Hagberg M | title = Muscular endurance and surface electromyogram in isometric and dynamic exercise | journal = Journal of Applied Physiology | volume = 51 | issue = 1 | pages = 1–7 | date = July 1981 | pmid = 7263402 | doi = 10.1152/jappl.1981.51.1.1 }}</ref><ref>{{cite journal | vauthors = Hawley JA, Reilly T | title = Fatigue revisited | journal = Journal of Sports Sciences | volume = 15 | issue = 3 | pages = 245–246 | date = June 1997 | pmid = 9232549 | doi = 10.1080/026404197367245 }}</ref> Mental fatigue results from prolonged periods of [[Cognition|cognitive]] activity which impairs cognitive ability, can manifest as [[sleepiness]], [[lethargy]], or [[directed attention fatigue]],<ref name="Marcora 2009 857–864">{{cite journal | vauthors = Marcora SM, Staiano W, Manning V | title = Mental fatigue impairs physical performance in humans | journal = Journal of Applied Physiology | volume = 106 | issue = 3 | pages = 857–864 | date = March 2009 | pmid = 19131473 | doi = 10.1152/japplphysiol.91324.2008 | citeseerx = 10.1.1.557.3566 | s2cid = 12221961 }}</ref> and can also impair physical performance.<ref name="Martin">{{cite journal |vauthors=Martin K, Meeusen R, Thompson KG, Keegan R, Rattray B |title=Mental Fatigue Impairs Endurance Performance: A Physiological Explanation |journal=Sports Med |volume=48 |issue=9 |pages=2041–2051 |date=September 2018 |pmid=29923147 |doi=10.1007/s40279-018-0946-9 |s2cid=49317682 |url=}}</ref>

Another definition is that fatigue is ''"a significant subjective sensation of weariness, increasing sense of effort, mismatch between effort expended and actual performance, or exhaustion independent from medications, chronic pain, physical deconditioning, [[Anemia|anaemia]], respiratory dysfunction, [[Depression (mood)|depression]], and sleep disorders"''.<ref name="pmid37180990">{{cite journal |last1=Camera |first1=Valentina |last2=Mariano |first2=Romina |last3=Messina |first3=Silvia |last4=Menke |first4=Ricarda |last5=Griffanti |first5=Ludovica |last6=Craner |first6=Matthew |last7=Leite |first7=Maria I |last8=Calabrese |first8=Massimiliano |last9=Meletti |first9=Stefano |last10=Geraldes |first10=Ruth |last11=Palace |first11=Jacqueline A |title=Shared imaging markers of fatigue across multiple sclerosis, aquaporin-4 antibody neuromyelitis optica spectrum disorder and MOG antibody disease |journal=Brain Communications |date=2 May 2023 |volume=5 |issue=3 |pages=fcad107 |doi=10.1093/braincomms/fcad107 |pmid=37180990 |pmc=10171455 }}</ref>

In up to a third of fatigue primary care cases, no medical or psychiatric diagnosis is found.<ref name="BMJ-Best-Practice-2023" /><ref name="Medically unexplained symptoms-2017"/><ref name="pmid31574939"/>

* [[endocrine disease]]s or [[Metabolic disorder|metabolic disorders]]: [[diabetes mellitus]], [[hypothyroidism]] and [[Addison's disease]];<ref name="Friedman">{{cite book |last1=Friedman |first1=Henry Harold |title=Problem-oriented Medical Diagnosis |date=2001 |publisher=Lippincott Williams & Wilkins |isbn=978-0-7817-2909-3 |pages=4–5 }}</ref>

In some areas, it has been proposed that fatigue be separated into primary fatigue, caused directly by a disease process, and ordinary or secondary fatigue, caused by a range of causes including exertion and also secondary impacts on a person of having a disease (such as disrupted sleep).<ref>{{cite news |last1=Carter |first1=Jonathan L. |title=Fatigue in Patients With Multiple Sclerosis |url=https://practicalneurology.com/articles/2018-july-aug/fatigue-in-patients-with-multiple-sclerosis |work=Practical Neurology |date=2018 |archive-date=2022-06-16 |archive-url=https://web.archive.org/web/20220616230104/https://practicalneurology.com/articles/2018-july-aug/fatigue-in-patients-with-multiple-sclerosis |url-status=live }}</ref><ref>{{cite journal | vauthors = Chalah MA, Riachi N, Ahdab R, Créange A, Lefaucheur JP, Ayache SS | title = Fatigue in Multiple Sclerosis: Neural Correlates and the Role of Non-Invasive Brain Stimulation | journal = Frontiers in Cellular Neuroscience | volume = 9 | page = 460 | year = 2015 | pmid = 26648845 | pmc = 4663273 | doi = 10.3389/fncel.2015.00460 | doi-access = free }}</ref><ref name="Gerber et al 2019">{{cite journal | vauthors = Gerber LH, Weinstein AA, Mehta R, Younossi ZM | title = Importance of fatigue and its measurement in chronic liver disease | journal = World Journal of Gastroenterology | volume = 25 | issue = 28 | pages = 3669–3683 | date = July 2019 | pmid = 31391765 | pmc = 6676553 | doi = 10.3748/wjg.v25.i28.3669 | doi-access = free }}</ref><ref>{{cite journal | vauthors = Hartvig Honoré P |title=Fatigue |journal=European Journal of Hospital Pharmacy |date=June 2013 |volume=20 |issue=3 |pages=147–148 |doi=10.1136/ejhpharm-2013-000309 |s2cid=220171226 |doi-access=free }}</ref><ref>{{cite journal |last1=Newland |first1=Pamela |last2=Starkweather |first2=Angela |last3=Sorenson |first3=Matthew |title=Central fatigue in multiple sclerosis: a review of the literature |journal=The Journal of Spinal Cord Medicine |date=3 July 2016 |volume=39 |issue=4 |pages=386–399 |doi=10.1080/10790268.2016.1168587 |pmid=27146427 |pmc=5102292 }}</ref><ref>{{cite journal |last1=Patejdl |first1=Robert |last2=Zettl |first2=Uwe K. |title=The pathophysiology of motor fatigue and fatigability in multiple sclerosis |journal=Frontiers in Neurology |date=27 July 2022 |volume=13 |doi=10.3389/fneur.2022.891415 |doi-access=free |pmid=35968278 |pmc=9363784 }}</ref> The ICD-11 MG22 definition of fatigue<ref>{{Cite web|url=https://icd.who.int/browse11/l-m/en#/http://id.who.int/icd/entity/1109546957|title=ICD-11 for Mortality and Morbidity Statistics|website=icd.who.int|access-date=2021-11-26|archive-date=2018-08-01|archive-url=https://archive.today/20180801205234/https://icd.who.int/browse11/l-m/en%23/http://id.who.int/icd/entity/294762853#/http://id.who.int/icd/entity/1109546957|url-status=live}}</ref> captures both types of fatigue; it includes fatigue that "occur[s] in the absence of... exertion... as a symptom of health conditions."{{medical citation needed|date=March 2024}}

Inflammation distorts neural chemistry, brain function and functional connectivity across a broad range of brain networks,<ref>{{cite journal |last1=Korte |first1=S Mechiel |last2=Straub |first2=Rainer H |title=Fatigue in inflammatory rheumatic disorders: pathophysiological mechanisms |journal=Rheumatology |date=November 2019 |volume=58 |issue=Suppl 5 |pages=v35–v50 |doi=10.1093/rheumatology/kez413 |pmid=31682277 |pmc=6827268 }}</ref> and has been linked to many types of fatigue.<ref name="pmid31447842"/><ref>{{cite journal |last1=Omdal |first1=Roald |title=The biological basis of chronic fatigue: neuroinflammation and innate immunity |journal=Current Opinion in Neurology |date=June 2020 |volume=33 |issue=3 |pages=391–396 |doi=10.1097/WCO.0000000000000817 |pmid=32304437 |s2cid=215819309 }}</ref> Findings implicate [[neuroinflammation]] in the [[etiology]] of fatigue in [[Autoimmunity|autoimmune]] and related disorders.<ref name="pmid34599320"/><ref name="pmid31447842"/> Low-grade [[inflammation]] may cause an imbalance between energy availability and expenditure.<ref>{{cite journal | pmc=5932180 | year=2018 | last1=Lacourt | first1=T. E. | last2=Vichaya | first2=E. G. | last3=Chiu | first3=G. S. | last4=Dantzer | first4=R. | last5=Heijnen | first5=C. J. | title=The High Costs of Low-Grade Inflammation: Persistent Fatigue as a Consequence of Reduced Cellular-Energy Availability and Non-adaptive Energy Expenditure | journal=Frontiers in Behavioral Neuroscience | volume=12 | page=78 | doi=10.3389/fnbeh.2018.00078 | pmid=29755330 | doi-access=free }}</ref>

Areas of the brain for which there is evidence of relation to fatigue are the [[thalamus]] and middle frontal cortex,<ref name="pmid26878885" /> fronto-parietal and cingulo-opercular,<ref name="pmid35221951" /> and default mode network, salience network, and thalamocortical loop areas.<ref name="Qi-2019" /><ref>{{cite journal |last1=Borghetti |first1=Lorraine |last2=Rhodes |first2=L. Jack |last3=Morris |first3=Megan B. |title=Fatigue Leads to Dynamic Shift in Fronto-parietal Sustained Attention Network |journal=Proceedings of the Human Factors and Ergonomics Society Annual Meeting |date=September 2022 |volume=66 |issue=1 |pages=606–610 |doi=10.1177/1071181322661056 |s2cid=253205546 }}</ref>

* [[Anemia|anaemia]], malignancies and other serious somatic diseases were only very rarely found in fatigued primary care patients, with prevalence rates hardly differing from non-fatigued patients.