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Release: Jan. 11, 2000

UI study helps clarify chronic fatigue definition and prognostic factors

IOWA CITY, Iowa -- People with chronic fatigue usually don't know why they have the fatigue, when they will get better or how to treat the fatigue. However, a recent University of Iowa study identifies prognostic characteristics for improvement of chronic fatigue.

The study found that certain patient characteristics helped predict which individuals with chronic fatigue would improve, said Arthur J. Hartz, M.D., Ph.D., UI professor of family medicine and the study's principal investigator and lead author. The study also raised questions about the current definition of chronic fatigue syndrome, a subclassification of unexplained chronic fatigue.

"We found that only some of the symptoms used to define chronic fatigue syndrome provide information about fatigue prognosis," said Hartz, who is also director of research in the UI department of family medicine.

In contrast to previous studies, the UI-led investigation examined patients who had idiopathic, or unexplained, chronic fatigue rather than only patients with the more narrowly labeled chronic fatigue syndrome. As a result, the study was able to compare the prognoses for chronic fatigue patients who had certain factors to the prognoses for chronic fatigue patients who did not have these factors.

"Most researchers have assumed that there is a special type of chronic fatigue called chronic fatigue syndrome," explained Hartz. "But there has been little empirical basis for the definition, making it somewhat subjective. It's important to better subclassify chronic fatigue for both research and clinical care purposes."

Unexplained chronic fatigue substantially impairs a person's quality of life but has no known medical or lifestyle cause. The investigators found that people with poor memory or poor concentration and symptoms not currently used to define chronic fatigue syndrome -- including backaches, indigestion, other stomach or intestinal problems or discomfort, mild fever or chills, dizziness and unexplained muscle weakness -- were less likely to recover from their fatigue.

The investigation also showed that less frequent sleep disruption, fewer hours sleeping overall and being married were also associated with fatigue improvement.

The study involved 199 Wisconsin patients with unexplained chronic fatigue lasting six or more months. The UI team collaborated with investigators at the Medical College of Wisconsin in Milwaukee and the George Washington School of Public Health in Washington, D.C.

The researchers evaluated questionnaires completed by participants, primarily women ages 30 to 55, to assess changes over a two-year period. Participants included members of the Wisconsin Chronic Fatigue Syndrome Association.

Chronic fatigue syndrome was first defined in 1988, then redefined in 1994. It is defined as idiopathic chronic fatigue plus any four of eight symptoms -- despite the lack of empirical support for the definition, Hartz explained. Those symptoms include: fatigue lasting more than 24 hours following exercise; memory or concentration problems; tiredness upon waking in the morning; a sore throat; tender cervical or axillary lymph nodes; muscle aches; joint pain; and headaches.

Hartz said the lack of empirical evidence for chronic fatigue syndrome may contribute to the lack of success in developing an effective laboratory test to identify people with the condition.

"There are no hard findings," he said. "Periodically, a laboratory test is reported to diagnose chronic fatigue syndrome, but so far these tests have not been substantiated. It will be difficult to develop the test before the condition is well defined."

Chronic fatigue is frustrating for patients and physicians alike because patients often do not respond to medication, said Hartz, who also investigates conventional and alternative treatment methods for unexplained chronic fatigue. He noted that physicians sometimes assume chronic fatigue is simply depression.

The relationship between depression and fatigue has always been of great interest, he said. "Although depression may cause fatigue, there is considerable evidence that depression is not the cause for many people with unexplained chronic fatigue," he said.

However, the UI-led study shows a linkage, Hartz added. Depression scores improved for many patients whose fatigue improved, not just for those who had been severely depressed.

"Although depression may underlie the fatigue for some patients, it is also possible that the fatigue may underlie the depression, or a third problem may underlie both," he said. "When this other problem improves, both the fatigue and depression may improve."

Hartz concluded, "The more information we have to classify patients with chronic fatigue, the better able we will be to focus the research, which can lead to improved clinical care."

The chronic fatigue findings appeared in the November/December issue of the Archives of Family Medicine. In addition to Hartz, the UI research team included Suzanne Bentler, research associate in family medicine.

The study was funded in part by a grant from the American Academy of Family Physicians.

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