Introduction
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.
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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; and
- 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.
For more detailed information regarding the definition of CFS,
please go to our
CFS
Definition section.
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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.
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Other Conditions That May Cause
Similar Symptoms
In addition, there are a large number of clinically defined,
frequently treatable illnesses that can result in fatigue.
Diagnosis of any of these conditions would exclude a definition
of CFS unless the condition has been treated sufficiently and no
longer explains the fatigue and other symptoms. These include
hypothyroidism, sleep apnea and narcolepsy, major depressive
disorders, chronic mononucleosis, bipolar affective disorders,
schizophrenia, eating disorders, cancer, autoimmune disease,
hormonal disorders*, subacute infections, obesity, alcohol or
substance abuse, and reactions to prescribed medications.
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Other Commonly Observed
Symptoms in CFS
In addition to the eight primary defining symptoms of CFS, a
number of other symptoms have been reported by some CFS
patients. The frequencies of occurrence of these symptoms vary
from 20% to 50% among CFS patients. They include abdominal pain,
alcohol intolerance, bloating, chest pain, chronic cough,
diarrhea, dizziness, dry eyes or mouth, earaches, irregular
heartbeat, jaw pain, morning stiffness, nausea, night sweats,
psychological problems (depression, irritability, anxiety, panic
attacks), shortness of breath, skin sensations, tingling
sensations, and weight loss.
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Risk Factors for CFS
- People of every age, gender, ethnicity and socioeconomic
group can have CFS.
- CFS affects women at four times the rate of men.
- Research indicates that CFS is most common in people in
their 40s and 50s.
- Although CFS is much less common in children than in
adults, children can develop the illness, particularly
during the teen years.
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Defining CFS
Symptoms
- CFS is marked by extreme fatigue that has lasted at
least six months; is not the result of ongoing effort; is
not substantially relieved by rest; and causes a substantial
reduction in daily activities.
- In addition to fatigue, CFS includes eight
characteristic symptoms:
- postexertional malaise (relapse of symptoms after
physical or mental exertion);
- unrefreshing sleep;
- substantial impairment in memory/concentration;
- muscle pain;
- pain in multiple joints;
- headaches of a new type, pattern or severity;
- sore throat; and
- 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.
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Diagnosis of CFS
- There are no physical signs that identify CFS
- There are no diagnostic laboratory tests for CFS.
- People who suffer the symptoms of CFS must be carefully
evaluated by a physician because many treatable medical and
psychiatric conditions are hard to distinguish from CFS.
Common conditions that should be ruled out through a careful
medical history and appropriate testing include
mononucleosis, Lyme disease, thyroid conditions, diabetes,
multiple sclerosis, various cancers, depression and bipolar
disorder.
- Research conducted by the Centers for Disease Control
and Prevention (CDC) indicates that less than 20% of CFS
patients in this country have been diagnosed.
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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.
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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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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.
