Ghalehbandi M, Khosravifar S, Aloosh O, et al. - Given the correlation of chronic obstructive pulmonary disease (COPD) with an increase in susceptibility to sleep disturbances, researchers herein examined the relationship between COPD severity criteria and sleep quality. Among 158 patients diagnosed with COPD, 125 patients were male (79%), and 33 were female (21%). Pittsburgh Sleep Quality Index (PSQI), COPD assessment test (CAT), modified Medical Research Council (mMRC) dyspnea scale, spirometry, and pulse oximetry were conducted among these patients. Analysis revealed a significant association of PSQI with the CAT and mMRC for COPD patients and its correlation with the disease's severity. The patients with higher CAT score described poor sleep quality, particularly in longer sleep latency, bad subjective sleep quality, lower sleep efficiency, higher sleep disturbance, daytime dysfunction, and sleep medication intake times a week.