Fatigue is a common complaint. Community-based epi-demiological studies suggest that at any given time approximately 10% of women and 5% of men suffer from fatigue of greater than 6 months' duration. However, because CFS requires severe, medically unexplained fatigue that is not resolved by rest, cannot be explained by medical or psychiatric illness, and is accompanied by specific symptoms, CFS itself is far less common. Prevalence rates vary significantly across studies, probably as a result of differences in diagnostic criteria and experimental design. Nevertheless, it appears that 0.3 to 1.6% of the population meet criteria for CFS. In the largest community-based epidemiological study conducted to date, researchers at the Centers for Disease Control and Prevention (CDC) found that 2% of women and 0.9% of men met CFS criteria based on phone interviews. However, when carefully evaluated by a trained clinician, most of these individuals failed to qualify for CFS because symptoms had changed or a potential medical or psychiatric exclusion was identified. Based upon these careful assessments, the CDC now estimates the prevalence of CFS to be 235 per 100,000 adults 18 to 69 years of age, or 0.24%.
Traditionally the prevalence rates for CFS have been thought to be highest in middle- and upper middle-class White females. It is now clear that this reflects a bias in early studies that recruited patients from medical practices. Large community-based epidemiological studies in the United States indicate that CFS is equally or more common in African Americans, Hispanics, and Native Americans and among individuals who earn less than
$40,000 per year. However, in all these groups, women are two to four times more likely than men to have CFS.
CFS is a chronic illness that waxes and wanes over time, and although patients report significant improvement, it is unclear if the illness completely resolves. Patients with CFS are strikingly disabled: Between 40 and 70% are unable to work or attend school, and 93% report severe impairment in their ability to perform daily life activities. Some evidence suggests that patients who develop CFS suddenly may have a better outcome than those who develop the illness insidiously over time.
Was this article helpful?