The Association between All-Cause Mortality and Obstructive Sleep Apnea in Adults: A U-Shaped Curve

Abstract

Rationale: The relationship between sleep apnea (SA) and mortality remains a topic of debate. Objectives: We explored the relationship between the severity of SA and mortality and the effect of age on this association. Methods: Using a veterans' database, we extracted an apnea-hypopnea index (AHI) from physician interpretations of sleep studies by developing a natural language processing pipeline (with 944 manually annotated notes), which achieved more than 85% accuracy. We categorized the participants into no SA (n-SA; AHI, <5), mild to moderate SA (m-SA; 5 ⩽ AHI < 30), and severe SA (s-SA; AHI, ⩾30). We propensity-matched the m-SA and s-SA categories with n-SA on the basis of age, sex, race, ethnicity, body mass index, and 38 components of the Elixhauser Comorbidity Index. Using logistic regression, we estimated the odds ratio (OR) for all-cause mortality using m-SA as a reference. Also, we stratified the findings on the basis of age: young, ⩽40; middle aged, >40 and <65; and older, ⩾65 adults. Results: We extracted the AHI on 179,121 propensity-matched participants (mean age = 45.85 [SD = 14.1]; BMI = 30.15 ± 5.37 kg/m²; male, 79.09%; White, 64.5%). All-cause mortality rates among three AHI categories showed a U-shaped curve (11.55%, 7.07%, and 8.15% for n-SA, m-SA, and s-SA, respectively), regardless of age group. Compared with m-SA, the odds of all-cause mortality in n-SA (OR, 1.72; 95% confidence interval = 1.65-1.79) and s-SA (OR, 1.17; 95% confidence interval = 1.12-1.22) were higher. Stratifying by age yielded consistent findings. Conclusions: All-cause mortality showed a U-shaped association with the AHI. Further investigations to understand the underlying mechanisms of this phenomenon are warranted.

Keywords: Apnea–Hypopnea index; intermittent hypoxia; mortality; natural language processing; sleep apnea.