0524 Examining the Relationship Between Positional Obstructive Sleep Apnea and Cardiovascular Outcomes: The Multi-Ethnic Study of Atherosclerosis

Abstract Introduction Positional obstructive sleep apnea (POSA) is characterized by obstructive events that occur predominantly in the supine position. This phenotype may be associated with lower cardiovascular risks than those without POSA. However, the causal relationship between POSA and cardiovascular (CV) outcomes remains unclear. Methods We used data from the Multi-Ethnic Study of Atherosclerosis (MESA) Exam 5 and beyond, along with polysomnography data from the Ancillary Sleep Study. Eligible participants had no prior CV events at Exam 5 and met the following criteria: apnea-hypopnea index (AHI – defined by the AASM’s 4% oxygen desaturation criterion) ≥ 5, a total sleep time (TST) ≥ 2 hours, and ≥ 30 minutes spent in both supine and non-supine positions. POSA was defined as a supine/non-supine AHI ratio ≥ 2. Outcomes included CV risk (measured using a continuous composite score of seven CV risk factors and analyzed by linear regression), as well as incidence of CV events, CV mortality, and all-cause mortality (analyzed by Cox proportional hazards regression). We estimated two models, one unadjusted and one adjusted for multiple potential confounders. Results The sample included 1,017 adults (mean age 68 ± 9, 52% female, 42% with POSA). The average AHI was 22.2 ± 16.3 (POSA vs. non-POSA: 19.6 vs. 25.8, p 0.001). Over an average 9.5-year follow-up, 111 participants experienced CV events, 34 died from CV causes, and 125 died from all causes. Compared with the non-POSA group, the POSA group showed a significantly lower CV risk in the unadjusted model (β: 0.28, 95% confidence interval CI: 0.08-0.49, p = 0.007). However, the relationship was attenuated after adjusting for the covariates (β: 0.15, 95% CI: -0.05 to 0.34, p = 0.137). No statistically significant between-group differences were observed in the hazards of incidence of CV events (adjusted hazard ratio aHR: 0.81, 95% CI: 0.55-1.18, p = 0.268), CV mortality (aHR: 0.79, 95% CI: 0.40-1.58, p = 0.506), or all-cause mortality (aHR: 0.86, 95% CI: 0.60-1.24, p = 0.421). Conclusion This study did not provide evidence for differences in CV outcomes in adults with and without POSA. However, future follow-up is needed to confirm the lack of association. Support (if any)