Purpose: The associations between obstructive sleep apnea (OSA) and all-cause and cardiovascular mortality are well established but are not entirely consistent. To accurately evaluate these associations as well as the therapeutic effects of continuous positive airway pressure (CPAP), we conducted a comprehensive meta-analysis of all eligible cohort studies.
Methods: Electronic literature databases (i.e., PubMed and Embase) were searched for relevant studies published before January 2016 that evaluated the associations between OSA and all-cause or cardiovascular mortality. Random-effect models were used to calculate the pooled hazard ratio (HR) and corresponding 95 % confidence intervals (CIs) for categorical risk estimates. The therapeutic effects of CPAP treatment for all-cause and cardiovascular mortality in OSA were examined through the meta-analysis.
Results: The 27 cohort studies included in the meta-analysis included 3,162,083 participants. Compared to the control group, the pooled HR of all-cause mortality was 1.19 (95 % CI, 0.86-1.65) for mild OSA, 1.28 (0.96-1.69) for moderate OSA, and 2.13 (1.68-2.68) for severe OSA. The pooled HR of cardiovascular mortality was 1.24 (0.53-2.55) for mild OSA, 2.05 (0.57-5.47) for moderate OSA, and 2.73 (1.94-3.85) for severe OSA. All-cause mortality (HR 0.66; 0.59-0.73) and cardiovascular mortality (HR 0.37; 0.16-0.54) were significantly lower in CPAP-treated than in untreated patients. There were no differences in cardiovascular mortality in CPAP-treated OSA patients vs. normal control subjects (HR 0.82; 0.52-1.29).
Conclusions: Greater attention should be paid to severe OSA, as it is an independent predictor for risk for all-cause and cardiovascular mortality. CPAP is an effective treatment that reduces risk of mortality.
Keywords: All-cause mortality; Cardiovascular mortality; Meta-analysis; Obstructive sleep apnea.