Purpose: Patients with chronic fatigue syndrome (CFS) report that exertion produces dramatic symptom worsening. We hypothesized this might be due to the exacerbation of an underlying sleep disorder, which we have previously demonstrated to exist.
Methods: Female patients with CFS and matched healthy controls with no evidence of major depressive disorder were studied with overnight polysomnography on a baseline night and on a night after their performance of a maximal exercise test.
Results: CFS patients as a group had evidence for disturbed sleep compared with controls. Although exercise improved sleep for healthy subjects, it did not do this for the group as a whole. When we stratified the sample on the basis of self-reported sleepiness after a night's sleep, the patient group with reduced morning sleepiness showed improvement in sleep structure, whereas those with increased morning sleepiness continued to show evidence for sleep disruption.
Conclusions: Sleep is disturbed in CFS patients as a group, but exercise does not exacerbate this sleep disturbance. Approximately half the patients studied actually sleep better after exercise. Therefore, activity-related symptom worsening is not caused by worsened sleep.