Objective, but not subjective, daytime sleepiness predicts mortality in obstructive sleep apnea

Study Objectives: Obstructive sleep apnea (OSA) with objective but not subjective excessive daytime sleepiness (EDS) has been reported to be associated with cardiovascular comorbidity. We aimed to investigate the association between OSA with objective or subjective EDS and mortality in a general population sample. Methods: In this retrospective cohort study, we included 244 subjects with OSA and 553 subjects without OSA with a median follow-up duration of 8 years. Objective EDS was defined based on a mean latency value of the multiple sleep latency test (MSL) <= 8 min. Subjective EDS was defined based on the total score of the Epworth Sleepiness Scale > 10. Results: After adjusting for potential confounders, OSA with objective EDS was associated with an approximately 2.5-fold higher risk of all-cause mortality (hazard ratio [HR] = 2.451, 95% confidence interval [95% CI] = 1.319 to 4.556) and 3.9-fold higher risk of CVD mortality (HR = 3.876, 95% CI = 1.293 to 11.622) compared to subjects without OSA or objective EDS. Furthermore, subjects with OSA, objective EDS, and CVD at baseline had about a 2.9-fold higher risk of all-cause mortality (HR = 2.872, 95% CI = 1.186 to 6.953) compared to subjects without OSA, objective EDS, or CVD at baseline. In contrast, OSA with subjective EDS was not associated with increased hazard of all cause or CVD mortality. Conclusions: Objective EDS appears to be an important marker of the biological severity of OSA. Future studies to validate the findings in diverse populations and interventional studies are needed.