The relationship between sleep quality and functional exercise capacity in COPD

Background Poor sleep is often associated with a series of health problems in patients with chronic obstructive pulmonary disease (COPD), but the relationship between sleep quality and functional exercise capacity has not been previously investigated. Aims To evaluate the relationship between quality of sleep and functional exercise capacity in clinically stable COPD. Methods One hundred three consecutive subjects with stable COPD were recruited. The subjects were assessed with the Pittsburgh Sleep Quality Index (PSQI) and divided into poor sleep group (PSQI >5) and good sleep group (PSQI ≤5). Subjects were also assessed with spirometry, 6‐min walk distance (6MWD), oxygen saturation (SPO2), the Epworth Sleepiness Scale, Hamilton Depression Rating Scale, Hamilton Anxiety Rating Scale, COPD Assessment Test (CAT), Modified Medical Research Council dyspnea scale and quadriceps muscle function. Results Poor sleep was present in 43.69% of the patients with COPD. Subjects with poor sleep had shorter 6MWD (t = −3.588, P