Modifiable risk factors for sleep apnea: evidence from meta-analysis of traditional observational studies and 2-sample mendelian randomization

Epidemiologic studies have linked several modifiable factors to the risk of sleep apnea (SA). However, which specific factors affect the risk of SA and the strength of these effects are unclear. We conducted meta-analyses based on cross-sectional, cohort, and case-control studies found in the PubMed, Scopus, and Web of Science databases up to August 1, 2023. Studies that reported 1 of the associations of education level, physical activity, sedentary behavior, smoking status, alcohol consumption, or coffee consumption with SA were included. Two independent investigators assessed the risk of bias using the Newcastle-Ottawa Scale and the Agency for Healthcare Research and Quality scale. Two-sample Mendelian randomization (MR) studies then were conducted to clarify the causality further. A total of 49 studies were included in the meta-analysis (N = 429 809 study participants). Compared with the other categorial groups, lower level of education (odds ratio [OR] = 1.58; 95% CI, 1.28-1.96), higher level of sedentary behavior (OR = 1.22; 95% CI, 1.01-1.47), current smoking status (OR = 1.33; 95% CI, 1.17-1.51), and current alcohol consumption (OR = 1.40; 95% CI, 1.33-1.48) were associated with higher risk of SA. Higher level of physical activity (OR = 0.77; 95% CI, 0.70-0.83) was associated with lower risk of SA. In the MR study, years of educational attainment were associated with a lower risk of SA (OR = 0.83; 95% CI, 0.78-0.88), and smoking initiation was associated with a higher risk of SA (OR = 1.10; 95% CI, 1.05-1.15). Prevention strategies for SA should focus on modifying these risk factors, especially reducing education inequalities and smoking initiation.