Abstract
Objective: To examine the presence of symptoms associated with chronic fatigue syndrome (CFS) over the course of the illness and determine the probability of self-defined recovery by duration of illness.
Design: Follow-up study.
Subjects: One hundred fifty-five CFS patients enrolled in the Centers for Disease Control and Prevention's (CDC) CFS surveillance system between August 1989 and July 1993 and followed to November 1997.
Measurements: Presence of symptoms, a self-defined period of recovery from CFS, and demographic differences between patients reporting and not reporting recovery. Period life-table methods were used to compute the probability of recovery from CFS for specific years of illness duration.
Results: At illness onset, the most commonly reported CFS symptoms (> 45%) were sore throat, fever, tender lymph nodes, general weakness, and muscle pain. As the illness progressed, the percentages of patients reporting symptoms fluctuated. At illness onset, patients with a sudden onset of CFS reported significantly higher frequencies of sore throat, fever, tender lymph nodes, chills, hypersomnia, difficulty thinking or concentrating, and depression when compared to patients with a gradual onset. As the illness progressed, these differences disappeared, but gradual onset cases reported more hypersomnia than sudden onset cases (p = 0.001). The cumulative probability of recovery from CFS was 31.4% during the first 5 years of illness and 48.1% during the first 10 years of illness. For each year of illness through year 15, both sudden and gradual onset cases had similar recovery probabilities. Thereafter, gradual onset cases had higher recovery probabilities, but these differences were not statistically significant. Patients reporting recovery and those remaining ill were similar demographically.
Conclusions: A period of recovery could be reported at any time during the course of CFS, but was more likely in the early years. Additional longitudinal studies are required to adequately describe the course of CFS in the early stages of illness, determine if the illness recurs over time, and predict the occurrence of symptoms over the course of illness. We recommend that researchers develop a standard definition of recovery from CFS and that future studies take into account the variable duration of illness and follow-up.