Study Objective: To determine the frequency of the chronic fatigue syndrome among patients with symptoms of fatigue.
Design: Prospective, cohort study.
Setting: Referral clinic, based in a primary care general internal medicine faculty practice of a university medical center.
Patients: Consecutive sample of 135 patients (53 men, 82 women) with 6 months or more of debilitating fatigue.
Interventions: All patients had a complete history taken, had a physical examination and a comprehensive battery of blood tests, and were given the Diagnostic Interview Schedule of the National Institute of Mental Health, a highly-structured 260-item instrument designed to enable accurate psychiatric diagnoses. Other diagnostic studies (for example, sleep studies and electroencephalography) were ordered if necessary for individual patients.
Measurements and Main Results: Six of the one hundred thirty-five patients met criteria for chronic fatigue syndrome (95% CI, 0 to 10). Ninety-one (67%) patients (CI, 56 to 78) had clinically active psychiatric disorders and 4 (3%) patients (CI, 0 to 8) had medical disorders that were considered a major cause of their fatigue. Thirty-four (25%) patients (CI, 14 to 36) had insufficient symptoms or objective findings of the chronic fatigue syndrome.
Conclusion: The chronic fatigue syndrome is rare among patients with symptoms of persistent fatigue. Most of these patients have psychiatric disorders.