Chronic Fatigue Syndrome (CFS)
Chronic fatigue syndrome, or CFS, is a debilitating and complex disorder characterized by profound fatigue that is not improved by bed rest and that may be worsened by physical or mental activity. Symptoms affect several body systems and may include weakness, muscle pain, impaired memory and/or mental concentration, and insomnia, which can result in reduced participation in daily activities.
Chronic fatigue syndrome, or CFS, is a devastating and complex disorder. People with CFS have overwhelming fatigue and a host of other symptoms that are not improved by bed rest and that can get worse after physical activity or mental exertion. They often function at a substantially lower level of activity than they were capable of before they became ill.
Besides severe fatigue, other symptoms include muscle pain, impaired memory or mental concentration, insomnia, and post-exertion malaise lasting more than 24-hours. In some cases, CFS can persist for years.
Researchers have not yet identified what causes CFS, and there are no tests to diagnose CFS. Moreover, because many illnesses have fatigue as a symptom, doctors need to take care to rule out other conditions, which may be treatable.
There are several case definitions for CFS and all require fatigue as one of the symptoms. CDC uses the 1994 CFS case definition, which requires meeting three criteria:
- The individual has had severe chronic fatigue for 6 or more consecutive months and the fatigue is not due to ongoing exertion or other medical conditions associated with fatigue (these other conditions need to be ruled out by a doctor after diagnostic tests have been conducted)
- The fatigue significantly interferes with daily activities and work
- The individual concurrently has 4 or more of the following 8 symptoms:
- post-exertion malaise lasting more than 24-hours
- un-refreshing sleep
- significant impairment of short-term memory or concentration
- muscle pain
- pain in the joints without swelling or redness
- headaches of a new type, pattern, or severity
- tender lymph nodes in the neck or armpit
- a sore throat that is frequent or recurring
These symptoms should have persisted or recurred during 6 or more consecutive months of illness, and they cannot have first appeared before the fatigue.
Causes of CFS
Despite a vigorous search, scientists have not yet identified what causes CFS. While a single cause for CFS may yet be identified, another possibility is that CFS has multiple triggers. Some of the possible causes of CFS might be:
- immune dysfunction
- abnormally low blood pressure that can cause fainting (neurally mediated hypotension)
- nutritional deficiency
- stress that activates the axis where the hypothalamus, pituitary, and adrenal glands interact (the HPA axis)
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