Association between remnant cholesterol-to-HDL-C ratio and obstructive sleep apnea risk in U.S. adults: a cross-sectional analysis of NHANES 2015-2018

BackgroundSeveral lipid ratios have been linked to obstructive sleep apnea (OSA) risk in NHANES, yet two questions central to clinical translation remain unanswered: how much of the association is carried by central adiposity, and whether the dose-response curve contains an actionable threshold. We addressed both for the remnant cholesterol-to-HDL-C ratio (RC/HDL-C). MethodsWe analysed 3,635 adults aged [&ge;]20 years from NHANES 2015-2018. OSA risk was ascertained from the Sleep Disorders Questionnaire. Multivariable logistic regression estimated odds ratios across three nested models. Restricted cubic splines and segmented regression characterised the dose-response and located the inflection point. Mediation by body roundness index (BRI) was quantified by nonparametric percentile bootstrap (1,000 resamples). Discrimination was compared by ROC analysis, with stratified and trimmed-sample sensitivity analyses. ResultsOSA risk was identified in 1,361 participants (37.4%). Each one-unit rise in RC/HDL-C carried 23% higher adjusted odds of OSA (OR 1.23, 95% CI 1.03-1.47); the highest quartile carried 49% higher odds than the lowest (P-trend < 0.001). The dose-response was nonlinear, with an inflection at RC/HDL-C = 0.232: below this point each 0.1-unit increase raised odds by 54% (OR 1.54, 95% CI 1.16-2.05); above it the curve plateaued. BRI mediated 82.7% of the total effect (ACME 0.039, P < 0.001), with the indirect pathway 2.8 times stronger in women. AUCs were 0.599 (BRI) and 0.564 (RC/HDL-C). ConclusionsRC/HDL-C showed a modest, threshold-shaped association with OSA risk in U.S. adults, with central adiposity (BRI) as the predominant mediating factor. These exploratory findings, based on questionnaire-defined OSA, warrant prospective validation in cohorts with polysomnography.