What is chronic fatigue syndrome?
Chronic fatigue syndrome (CFS) is a disorder that causes ongoing, extreme fatigue that is not explained by any known medical condition. It can affect a person's ability to perform routine, daily activities or tasks.
People with CFS sleep poorly and awake unrefreshed. They have frequent headaches, muscle and joint pain, recurring sore throats, and memory and concentration problems. The intensity and type of symptoms can vary from day to day and from person to person, but typically the extreme fatigue lasts at least 6 months or more. On a "good day," symptoms may be mild and someone with CFS may be able to function at a near normal level; on a "bad day," they may be unable to get out of bed. Their condition is not improved by bed rest and can be worsened by mental activity.
CFS exists worldwide in every age, income bracket, and ethnic group, and in both sexes. CFS is about three to four times more common in women than in men and it appears to be most prevalent in the 40- to 50-year age range. The Centers for Disease Control and Prevention (CDC) estimates that at least one million people in the U.S have CFS but that less than 20% of those affected have been diagnosed or know that they have the condition.
It is not known what causes CFS. While a single cause may yet be identified, many researchers believe that CFS has multiple triggers. These may include:
- Viral infection such as Epstein Barr virus, although no microbe has been proven to be the cause
- Immune dysfunction provoked by trauma, stress, or allergy, which in turn triggers CFS
- Nutritional deficiency
- Abnormally low blood pressure (neurally mediated hypotension) that can cause fainting
- Disturbance of the hypothalamic-pituitary-adrenal (HPA) axis, possibly caused by inactivity, sleep disturbance, psychiatric comorbidity, medication, or ongoing stress
Researchers have observed family patterns and believe there may be a tendency to an inherited predisposition of the condition. Some investigators feel that further research will reveal that CFS is not a single condition at all but a group of different disorders with a similar end point.
It is known that those affected by CFS have a definite onset of symptoms, that is, a time before which they felt well and had the energy for normal daily tasks. About 75% of the time, CFS is preceded by what appears to be a flu-like illness. Other cases of CFS arise following a period of intense physical or emotional stress, and some emerge slowly with those affected noticing a gradual decline in their energy and sense of well-being.
A large number of other diseases, disorders, and temporary conditions can cause or display similar symptoms or side effects. Examples include hypothyroidism, mononucleosis, psychological disorders, eating disorders, cancer, autoimmune disease, infections, drug or alcohol abuse, reactions to prescription medications, and – for whatever reason – not getting enough hours of uninterrupted sleep. In these cases, an underlying reason for the fatigue can be established and often treated. This temporary, short-term, or long-term fatigue must be distinguished from CFS.
To date, there is no single test or evaluation that can diagnose CFS. However, there is a set of signs and symptoms used as criteria to help identify it. (See the next section.)