Daytime functioning in obstructive sleep apnea patients: Exercise tolerance, subjective fatigue, and sleepiness

A sample of 32 obstructive sleep apnea patients (27 males, 5 females) was a ssessed with overnight polysomnography and the Multiple Sleep Latency Test (MSLT), an objective measure of daytime sleepiness. Patients also participa ted in a maximal exercise test which served as an objective indicator of ph ysical fatigue. The Fatigue Severity Scale (FSS) was used as a subjective m easure of fatigue. Subjective fatigue ratings were significantly correlated with percent of predicted maximum heart rare achieved during exercise rest ing, suggesting that self-reported fatigue in apnea patients may refer to r educed physical fitness. FSS scores and exercise testing results were not s ignificantly correlated with the MSLT indicating that daytime fatigue and d aytime sleepiness are independent problems in apnea patients. Participants self-reported a high level of fatigue, and exercise testing revealed decrea sed physical work capacity among apnea patients, bur objective and subjecti ve indicators of fatigue were not significantly correlated with apnea sever ity. A higher percentage of REM sleep predicted greater work capacity.