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Prospective Study of the Prognosis of Unexplained Chronic Fatigue in a Clinic-Based Cohort

University of Texas at El Paso (K.B.S., J.O.B.), El Paso, TX; and University of Washington (J.I.F., D.S.B., W.J.K.), Seattle, WA.

Address reprint requests to: Karen B. Schmaling, PhD, Office of the Provost, University of Texas at El Paso, 500 W. University Ave., El Paso, TX 79968. E-mail: schmaling{at}utep.edu

OBJECTIVES: To determine prospective changes in clinical status related to chronic fatigue over an 18-month period, and to test demographic and clinical predictors of outcome.

METHODS: A cohort of 100 patients with unexplained chronic fatigue (UCF), which encompasses both chronic fatigue syndrome (CFS) and idiopathic chronic fatigue (ICF), completed questionnaire measures and medical and psychiatric evaluations on four occasions, each six months apart.

RESULTS: Approximately 21% of the sample did not meet criteria for either CFS or ICF at their last research appointment 1.5 years after their index visit. Vitality increased over time, and physical functioning tended to improve, but UCF symptoms did not decrease significantly. Less education, being unemployed, worse mental health, more use of sedating and antidepressant medications, and more somatic attributions for their symptoms were associated with worsening symptom severity over time. Older age, current depression, and more somatic attributions predicted worsening physical functioning. Better mental health, less use of sedating medications, and fewer somatic attributions for illness were significant predictors of increases in vitality.

CONCLUSIONS: Demographic and clinical variables predict outcomes over time among a cohort of patients with unexplained chronic fatigue.

Key Words: chronic fatigue, • prognosis, • prospective, • prediction, • attribution, • depression.

Abbreviations: CFC = Chronic Fatigue Clinic;; CFS = chronic fatigue syndrome;; DIS = Diagnostic Interview Schedule;; ICF = idiopathic chronic fatigue;; M = mean;; N = sample size;; SD = standard deviation;; UCF = unexplained chronic fatigue.