0535 The Effect of Positional Dependency on Obesity-Related Worsening of Obstructive Sleep Apnea

Introduction Positional obstructive sleep apnea (OSA) (POSA) is a common phenotype in which airway obstruction is significantly increased during supine sleep. Obesity can increase OSA severity, and in this study, we hypothesized that the effect of obesity may be different depending on the positional phenotype of OSA. Methods This retrospective, cross-sectional study involved newly diagnosed OSA patients (apnea-hypopnea index [AHI] ≥ 5/h) undergoing full-night polysomnography. The POSA group included patients with a supine AHI more than twice the non-supine AHI. We compared clinical characteristics across four subgroups: POSA without obesity (POSA-N), POSA with obesity (POSA-O), NPOSA without obesity (NPOSA-N), and NPOSA with obesity (NPOSA-O). The relationship between body mass index (BMI) and AHI in both groups, POSA and NPOSA (non-positional OSA), was analyzed using multivariate linear regression. We used analysis of covariance (ANCOVA) in order to find out the way positional dependency, obesity, and their interaction affected AHI. Results A total of 630 patients (mean age 52.2 ± 15.1 years; 72.5% male) were included, with 71.1% classified as POSA and 28.9% as NPOSA. Mean AHI was significantly higher in the NPOSA-O (69.1 ± 28.5) than in the other three groups (POSA-N 26.2 ± 14.7; POSA-O 35.6 ± 21.3; NPOSA-N 40.1 ± 26.6). Multivariate regression demonstrated BMI as an independent risk factor for AHI in both POSA (B = 0.361, p < 0.001) and NPOSA (B = 0.509, p < 0.001). A significant interaction between obesity and positional dependency on AHI was observed (F = 23.48, p < 0.001), indicating that obesity increases OSA severity more in patients with NPOSA than POSA. Conclusion Obesity-related OSA severity increase was more prominent in NPOSA than POSA. BMI and positional dependency can be used to stratify risk and improve individualized treatment strategies. Support (if any)