Obstructive sleep apnea, COPD, the overlap syndrome, and mortality: results from the 2005–2008 National Health and Nutrition Examination Survey

Objective The aim of this study was to investigate the role of obstructive sleep apnea (OSA) on all-cause mortality in patients with COPD. Methods Data for this cross-sectional study were obtained from the National Health and Nutrition Examination Survey (NHANES) data (year 2005-2008). Eligible subjects were ≥20 years who had no COPD or OSA (n=9,237), had only OSA (n=366), had only COPD (n=695), and had OSA/COPD overlap syndrome (n=90). Univariate and multivariate analyses were used to evaluate factors associated with overall mortality. Results Multivariate analysis found that the COPD and OSA/COPD overlap syndrome groups had significantly higher chance of all-cause mortality than the group of subjects who did not have OSA or COPD (adjusted hazard ratio [HR] =1.5 for the COPD group and 2.4 for the overlap syndrome group) (P≤0.007). Although not significant, having OSA/COPD overlap syndrome was associated with higher likelihood of death than COPD alone (HR =1.5; P=0.160). Other factors associated with higher overall mortality were aging, poorer family status, current smoker, serum vitamin D deficiency, cardiovascular disease, history of cancer, diabetes, and impaired renal function. Conclusion The present study found that COPD and OSA/COPD overlap syndrome were associated with higher all-cause mortality compared with patients without either disease and that OSA did not significantly increase mortality in patients with COPD.