Chronic Fatigue Syndrome

From Centers for Disease Control and Prevention

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. Persons with CFS most often function at a substantially lower level of activity than they were capable of before the onset of illness. In addition to these key defining characteristics, patients report various nonspecific symptoms, including weakness, muscle pain, impaired memory and/or mental concentration, insomnia, and post-exertional fatigue lasting more than 24 hours. In some cases, CFS can persist for years. The cause or causes of CFS have not been identified and no specific diagnostic tests are available. Moreover, since many illnesses have incapacitating fatigue as a symptom, care must be taken to exclude other known and often treatable conditions before a diagnosis of CFS is made.

A variety of studies by CDC and others have shown that between 1 and 4 million Americans suffer from Chronic Fatigue Syndrome (CFS). They are seriously impaired, at least a quarter are unemployed or on disability because of CFS. Yet, only about half have consulted a physician for their illness. The earlier a person with CFS receives medical treatment the greater the likelihood that the illness will resolve. Equally important, about 40% of people in the general population who report symptoms of CFS have a serious, treatable, previously unrecognized medical or psychiatric condition (such as diabetes, thyroid disease, substance abuse). CFS is a serious illness and poses a dilemma for patients, their families, and health care providers.

Similar Medical Conditions

A number of illnesses have been described that have a similar spectrum of symptoms to CFS. These include fibromyalgia syndrome, myalgic encephalomyelitis, neurasthenia, multiple chemical sensitivities, and chronic mononucleosis. Although these illnesses may present with a primary symptom other than fatigue, chronic fatigue is commonly associated with all of them.

Definition of CFS

A great deal of debate has surrounded the issue of how best to define CFS. In an effort to resolve these issues, an international panel of CFS research experts convened in 1994 to draft a definition of CFS that would be useful both to researchers studying the illness and to clinicians diagnosing it. In essence, in order to receive a diagnosis of chronic fatigue syndrome, a patient must satisfy two criteria:

• Have severe chronic fatigue of six months or longer duration with other known medical conditions excluded by clinical diagnosis
• Concurrently have four or more of the following symptoms: substantial impairment in short-term memory or concentration; sore throat; tender lymph nodes; muscle pain; multi-joint pain without swelling or redness; headaches of a new type, pattern or severity; unrefreshing sleep; and post-exertional malaise lasting more than 24 hours
• The symptoms must have persisted or recurred during six or more consecutive months of illness and must not have predated the fatigue

CFS Symptoms

In addition to fatigue, CFS includes eight characteristic symptoms:

1. postexertional malaise (relapse of symptoms after physical or mental exertion)
2. unrefreshing sleep
3. substantial impairment in memory/concentration
4. muscle pain
5. pain in multiple joints
6. headaches of a new type, pattern or severity
7. sore throat
8. tender neck or armpit lymph nodes

Symptoms and their consequences can be severe. CFS can be as disabling as multiple sclerosis, lupus, rheumatoid arthritis, congestive heart failure and similar chronic conditions. Symptom severity varies from patient to patient and may vary over time for an individual patient.

Possible Causes of CFS

Despite an intensive, nearly 20-year search, the cause of CFS remains unknown. Many different infectious agents and physiologic and psychological causes have been considered, and the search continues.

Much of the ongoing research into a cause has centered on the roles of the immune, endocrine and nervous systems may play in CFS. More recently, interactions among these factors are under evaluation.

Genetic and environmental factors may play a role in developing and/or prolonging the illness, although more research is needed to confirm this. CDC is applying cutting-edge genomic and proteomic tools to understand the origins and pathogenesis of CFS.

CFS is not caused by depression, although the two illnesses often coexist, and many patients with CFS have no psychiatric disorder.

Treatment of CFS

Since there is no known cure for CFS, treatment is aimed at symptom relief and improved function. A combination of drug and nondrug therapies is usually recommended. No single therapy exists that helps all CFS patients.

Lifestyle changes, including prevention of overexertion, reduced stress, dietary restrictions, gentle stretching and nutritional supplementation, are frequently recommended in addition to drug therapies used to treat sleep, pain and other specific symptoms.

Carefully supervised physical therapy may also be part of treatment for CFS. However, symptoms can be exacerbated by overly ambitious physical activity. A very moderate approach to exercise and activity management is recommended to avoid overactivity and to prevent deconditioning.

Although health care professionals may hesitate to give patients a diagnosis of CFS for various reasons, it’s important to receive an appropriate and accurate diagnosis to guide treatment and further evaluation.

Delays in diagnosis and treatment are thought to be associated with poorer long-term outcomes. For example, CDC’s research has shown that those who have CFS for two years or less were more likely to improve. It’s not known if early intervention is responsible for this more favorable outcome; however, the longer a person is ill before diagnosis, the more complicated the course of the illness appears to be.

Recovery from CFS

CFS affects each individual differently. Some people with CFS remain homebound and others improve to the point that they can resume work and other activities, even though they continue to experience symptoms.

Recovery rates for CFS are unclear. Improvement rates varied from 8% to 63% in a 2005 review of published studies, with a median of 40% of patients improving during follow-up. However, full recovery from CFS may be rare, with an average of only 5% to 10% sustaining total remission.

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