Having chronic fatigue syndrome appears to be associated with an increased risk of developing other physical health problems, suggest the results of a small study of identical and fraternal twins.
"Physicians should assess CFS patients for the presence of additional clinical conditions," said lead author Leslie A. Aaron, PhD, MPH, of the Department of Medicine at University of Washington. "Patients with chronic fatigue may present a complex clinical picture that poses diagnostic and management challenges."
Aaron and colleagues screened hundreds of twin pairs to find 127 pairs in which one twin had chronic fatigue for at least six months while the other did not suffer from fatigue. The researchers chose to compare twins using a co-twin study design because this method matches twins with regard to nearly identical early environment and genetics.
Study participants with chronic fatigue had higher rates of several physical conditions -- most notably fibromyalgia (a condition that causes muscle pain), irritable bowel syndrome, chronic pelvic pain, multiple chemical sensitivities and temporomandibular disorder (a condition that causes jaw pain) -- than did their twins, the researchers found.
The largest disparities between twins were noted in cases of fibromyalgia and irritable bowel syndrome. Seventy percent of those with chronic fatigue also had fibromyalgia, compared with 10 percent of their twins, and 50 percent of those with chronic fatigue also had irritable bowel syndrome, compared with 5 percent of their twins.
These illnesses share unknown causes and cannot always be diagnosed using laboratory or physical tests. Also stress appears to worsen their symptoms, according to the researchers. These illnesses are sometimes thought to be more mental than physical in origin, but Aaron and colleagues found psychiatric illness could not solely explain the high rates of overlap between chronic fatigue and the other conditions.
"All of these conditions represent complex interactions of biological, psychological and environmental factors," said Aaron.
The study results are published in the January 2001 issue of the Journal of General Internal Medicine.
The conditions found to overlap with chronic fatigue in this study may compound this condition's already high costs -- high unemployment and disability rates and high health care expenses. "Our findings should alert providers to the potentially devastating effects of these conditions and argue for early identification and appropriate treatment for each of the clinical conditions detected," noted Aaron.
Future research should focus on determining the exact relationship of genetic and environmental factors of CFS and related illnesses, as well as investigate the effectiveness of early treatment, according to the researchers.
This study was supported by a grant from the National Institute of Allergy and Infectious Diseases and the Arthritis Foundation.
The Journal of General Internal Medicine, a monthly peer-reviewed journal of the Society of General Internal Medicine, publishes original articles on research and education in primary care. For information about the journal, contact Renee F. Wilson at (410) 955-9868.
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