Association between endothelial cell activation and stress index and prevalence of obstructive sleep apnea: a cross-sectional study from the United States

Abstract Background Obstructive sleep apnea (OSA) is a prevalent sleep disorder closely linked to endothelial dysfunction. This study aimed to evaluate the utility of three distinct endothelial cell activation and stress index (EASIX) variants in patients with OSA and to investigate their associations with this condition. Methods This cross-sectional analysis utilized data from the National Health and Nutrition Examination Survey 2017–2020, encompassing US adults aged 20 years and older. Logistic regression models, adjusted for multiple covariates, were employed to assess the relationships between EASIX variants and OSA. Smooth curve fitting was conducted to explore nonlinear patterns and potential threshold effects, and subgroup analyses were performed to identify variations across different demographic and clinical strata. Results In this study, both the original EASIX and the modified EASIX (m-EASIX) scores were significantly higher in individuals with OSA than in those without. After full adjustment for relevant confounders, m-EASIX demonstrated a curvilinear relationship with OSA. Below a threshold of 3.32, m-EASIX was positively associated with OSA (OR = 1.117, 95% CI: 1.048–1.190, p = 0.006). Conversely, above 3.32, m-EASIX exhibited an inverse association (OR = 0.980, 95% CI: 0.966–0.995, p = 0.007). Stratified analyses further confirmed the robustness of these associations, and alcohol consumption emerged as a significant effect modifier in the m-EASIX–OSA interaction. Conclusion The m-EASIX may serve as a more suitable indicator for evaluating endothelial dysfunction in OSA, particularly when its value is below 3.32.