Biological aging as a mediator of the weight-adjusted waist index’s association with obstructive sleep apnea symptom risk and mortality in adults: evidence from a NHANES cohort study

The weight-adjusted waist index (WWI) has been proposed as a novel anthropometric marker for assessing metabolic and cardiovascular risk. However, its relationship with obstructive sleep apnea syndrome (OSAS) and its associated mortality remains inadequately explored. This study analyzed data from 2005–2008 and 2015–2018 cycles of the National Health and Nutrition Examination Survey. Weighted multivariable logistic regression and restricted cubic spline (RCS) analyses were conducted to evaluate the association between WWI and OSAS risk. Subgroup analyses were performed to examine variations across demographic and clinical strata. Biological aging was estimated using phenotypic age (PhenoAge), and mediation analysis was conducted to assess its role in the WWI-OSAS association. Cox proportional hazards models were used to determine the relationship between WWI and both all-cause mortality among individuals with OSAS. RCS regression was employed to explore potential nonlinear associations between WWI and mortality outcomes. Among 15,750 participants, 4723 (29.99%) were diagnosed with OSAS. A higher WWI was significantly associated with an increased risk of OSAS (odds ratio [OR] = 1.194, 95% confidence interval [CI] 1.100–1.297, P < 0.001). In individuals with OSAS, Cox regression models indicated that elevated WWI was independently linked to a higher all-cause mortality rate (hazard ratio [HR] = 1.479, 95%CI 1.228–1.781, P < 0.001). The RCS analyses demonstrated a robust positive linear association between WWI and the risk of OSAS (P for overall < 0.001), as well as between WWI and all-cause mortality among individuals with OSAS (P for overall < 0.001). Higher WWI is linked to a greater risk of OSAS on its own, partly due to biological aging, and is also connected to a higher mortality risk in people with OSAS.