Nonlinear age-related differences in clinical profiles of obstructive sleep apnea: a cross-sectional study of 1,508 Chinese patients

PURPOSE: To characterize age-related clinical profiles and nonlinear age associations in treatment-naive Chinese patients with obstructive sleep apnea (OSA). METHODS: This retrospective cross-sectional study included 1,508 patients aged 18-88 years at Peking Union Medical College Hospital (2022-2025). Clinical and polysomnographic characteristics were compared across five age groups. Restricted cubic splines assessed continuous-age associations, with separate overall and nonlinearity tests and sex-adjusted sensitivity analyses. Sex-adjusted logistic models evaluated prevalent severity, sleepiness, and cardiometabolic comorbidities; age-quartile comparisons were supplementary. RESULTS: Among 1,840 participants undergoing PSG, OSA detection differed across ages, with a greater increase among women (age-by-sex interaction P = 0.031). Respiratory severity was broadly comparable across age groups. In unadjusted analyses, body mass index and Epworth Sleepiness Scale scores showed nonlinear age associations (both P < 0.001), as did lowest oxygen saturation (P = 0.018) and selected Pittsburgh Sleep Quality Index (PSQI) components. Global PSQI was associated with age overall, without clear nonlinearity (P = 0.099). Sex adjustment attenuated nonlinearity for oxygen saturation and sleep latency. Older age was associated with higher prevalence odds of hypertension, cardiovascular disease, and diabetes. Excessive daytime sleepiness showed a midlife elevation. CONCLUSION: OSA clinical profiles differ across ages, with nonlinearity in selected measures. Older patients have greater comorbidity burden and poorer reported sleep quality despite comparable respiratory severity.