Sleep disordered breathing and mortality: eighteen-year follow-up of the Wisconsin sleep cohort

Abstract

Background: Sleep-disordered breathing (SDB) is a treatable but markedly under-diagnosed condition of frequent breathing pauses during sleep. SDB is linked to incident cardiovascular disease, stroke, and other morbidity. However, the risk of mortality with untreated SDB, determined by polysomnography screening, in the general population has not been established.

Methods: An 18-year mortality follow-up was conducted on the population-based Wisconsin Sleep Cohort sample (n = 1522), assessed at baseline for SDB with polysomnography, the clinical diagnostic standard. SDB was described by the number of apnea and hypopnea episodes/hour of sleep; cutpoints at 5, 15 and 30 identified mild, moderate, and severe SDB, respectively. Cox proportional hazards regression was used to estimate all-cause and cardiovascular mortality risks, adjusted for potential confounding factors, associated with SDB severity levels.

Results: All-cause mortality risk, adjusted for age, sex, BMI, and other factors was significantly increased with SDB severity. The adjusted hazard ratio (HR, 95% CI) for all-cause mortality with severe versus no SDB was 3.0 (1.4,6.3). After excluding persons who had used CPAP treatment (n = 126), the adjusted HR (95% CI) for all-cause mortality with severe versus no SDB was 3.8 (1.6,9.0); the adjusted HR (95% CI) for cardiovascular mortality was 5.2 (1.4,19.2). Results were unchanged after accounting for daytime sleepiness.

Conclusions: Our findings of a significant, high mortality risk with untreated SDB, independent of age, sex, and BMI underscore the need for heightened clinical recognition and treatment of SDB, indicated by frequent episodes of apnea and hypopnea, irrespective of symptoms of sleepiness.

Figure 1

Kaplan-Meier estimates of survival probability according to sleep-disordered breathing severity for A) Total sample and B) Sample excluding 126 CPAP treated participants. A. Kaplan-Meier estimates of the probability of survival (shown with y-axis truncated at 50% survival) according to sleep disordered breathing severity: none (AHI < 5), mild (AHI > 5, < 15), moderate (AHI > 15, < 30) and severe (AHI > 30), total sample (n = 1522); long-rank test for differences in survival by SDB category: P < 0.00001; AHI is mean number of apnea and hypopnea episodes/hr of sleep. B. Kaplan-Meier estimates of the probability of survival (shown with y-axis truncated at 50% survival) according to untreated* sleep-disordered breathing category (none (AHI < 5), mild (AHI > 5, < 15), moderate (AHI > 15, < 30) and severe (AHI > 30), *participants who had used CPAP were excluded (n = 1396); long-rank test for differences in survival by SDB category: P < 0.00001; AHI is mean number of apnea and hypopnea episodes/hr of sleep.