Background and objective: Previous reports have shown that patients with chronic obstructive pulmonary disease (COPD) sleep poorly, but the underlying basis remains speculative. The aim of this retrospective study was to determine potential predictors of poor sleep quality in COPD patients.
Methods: This is a secondary analysis of two previously published trials investigating the impact of long-acting bronchodilators on nocturnal oxygen saturation in moderate to severe COPD patients. One hundred and six patients with established COPD were studied. Each patient underwent overnight polysomnography studies in a dedicated university-affiliated sleep laboratory. Epworth Sleepiness Scores, spirometry and daytime arterial oxygen tension (PaO2) were also recorded. Univariate and multivariate analysis sought independent predictors of sleep quality from baseline demographic, spirometry and oximetry values.
Results: Patients' age was 66.4 ± 7.3 years (mean ± standard deviation), forced expiratory volume in 1 s (FEV1) 33.4 ± 12.9% predicted and daytime PaO2 64 ± 7.5 mm Hg. In comparison with historical normative populations, the cohort demonstrated impaired sleep quality. Sleep efficiency was 66 ± 17% and sleep stage analysis revealed altered architecture with diminished periods of rapid eye movement sleep (12.7 ± 8.3%). In multivariate analysis, daytime PaO2 correlated independently with sleep efficiency (P = 0.041), whereas FEV1 positively correlated with arousal index, and age correlated negatively with rapid eye movement sleep duration.
Conclusions: Sleep quality is poor in patients with severe COPD compared with normative populations of similar age, and daytime hypoxaemia is independently associated with impaired sleep efficiency.