Inflammation mediates the Pace of aging based on DNA methylation on mortality from NHANES 1999–2002: a national prospective cohort study

BACKGROUND: Global population aging underscores the urgent need for biomarkers quantifying biological aging trajectories. While DNA methylation-derived pace of aging (DunedinPoAm) measures individual differences, its generalizability across diverse populations and mechanistic links to systemic inflammation remain underexplored. This study aimed to systematically examine the longitudinal associations between the DunedinPoAm and all‑cause mortality in a multiethnic cohort, and to quantify the extent to which systemic inflammatory biomarkers mediate these associations using causal mediation analysis. METHODS: For this cohort study, information on a nationally representative cohort of 21,004 U.S. adults was extracted from the National Health and Nutrition Examination Survey (NHANES) conducted from 1999 to 2002, along with the NHANES Linked Mortality File, which ascertained mortality through December 31, 2019. The exposures were Pace of aging (DunedinPoAm) and inflammation. The survival outcome measured was all-cause mortality. We employed Cox proportional hazards models, Kaplan-Meier survival curves, restricted cubic splines, and Bayesian mediation frameworks to evaluate mortality risk, explore non-linear dose-response relationships, and investigate inflammatory mediation. RESULTS: Data were analyzed from 2,532 participants, with a mean follow-up duration of 18.5 ± 1.29 years. Higher DunedinPoAm quartiles exhibited graded mortality risks (Q4 vs. Q1: HR = 2.50, 95% CI 1.84-3.38), which persisted after multivariable adjustment. Restricted cubic splines revealed a non-linear association (P for overall < 0.001; P for nonlinearity < 0.001), indicating the presence of threshold effects. Systemic inflammation mediated 2.33-23.5% of the mortality risk associated with DunedinPoAm, driven by CD4 + T cells, B cells, CRP and comprehensive inflammatory indices. A significant interaction with diabetes (P for interaction = 0.026) underscored metabolic dysregulation as a vulnerability factor. CONCLUSION: DunedinPoAm predicts all-cause mortality in a non-linearly manner across multiethnic populations, partially mediated by pathways associated with inflammaging. The observed diabetes-specific interactions and threshold effects indicate the potential for precision approaches targeting high-risk subgroups. These findings support the integration of DunedinPoAm into gerotherapeutic trials and public health strategies aimed at addressing disparities in aging.