Nocturnal oxygen saturation is associated with all-cause mortality: a community-based study

Observational studies have demonstrated the association between the single-point measurement of oxygen saturation (SpO2) level and mortality in the general population. This study aimed to evaluate whether nocturnal SpO2 level could predict all-cause mortality in a community-based population.The study samples were obtained from the Sleep Heart Health Study, which included 2,280 men and 2,606 women (mean age, 63.8 ± 11.1 years). A pulse oximeter based on overnight in-home polysomnography was used to monitor SpO2 levels during total sleep time (SpO2-TOTAL). Multivariable Cox proportional hazards analysis was performed to examine the association between nocturnal SpO2 and all-cause mortality.During the follow-up period of 10.7 ± 3.0 years, 1110 (22.7%) people died. After adjusting for confounding factors, multivariable Cox regression analysis showed that the average SpO2-TOTAL (hazard ratio [HR] 0.93; 95% confidence interval [CI] 0.90-0.96, P<0.001) was associated with all-cause mortality. These findings remained stable in individuals with low and high apnea-hypopnea index levels. Additionally, maximum SpO2-TOTAL (HR, 0.91; 95% CI, 0.87-0.96; P = 0.001) and minimum SpO2-TOTAL (HR, 0.98; 95% CI, 0.97-0.99; P = 0.001) could predict all-cause mortality. A significant association between nocturnal hypoxemia and all-cause mortality was also observed.Our findings highlights the importance of monitoring nocturnal SpO2 level and improving hypoxemia in the general populations.