Association Between Relative Fat Mass and Cardiometabolic Disease: Age-Stratified Analysis in Young and Middle-Aged Versus Older Adults.

Background: Current evidence characterizing the association between relative fat mass (RFM) and cardiometabolic disease (CMD) remains limited, with critical gaps persisting in the understanding of age-dependent heterogeneity. Thus, this study aimed to assess the association between RFM and CMD risk across age groups. Methods: This study utilized data from the China Health Evaluation And Risk Reduction Through Nationwide Teamwork (ChinaHEART), and enrolled 93,801 community-dwelling adults. CMD was defined as a composite diagnosis that included diabetes mellitus, myocardial infarction, and stroke. Meanwhile, RFM was derived from height, waist circumference, and sex. Participants were stratified into groups of young and middle-aged adults (35-59 years) and older adults (≥60 years). Multivariable logistic regression models were employed to estimate odds ratios (ORs) and 95% confidence intervals (CIs), and to test for interaction effects. Restricted cubic spline models were applied to examine dose-response relationships. Results: Among the 93,801 participants, 18,473 (19.69%) had CMD. In the fully adjusted models, each unit increase in RFM was associated with a 9% increase in CMD risk (OR = 1.09, 95% CI: 1.08-1.09). Compared to the lowest RFM quartile (Q1), higher risks were observed in the Q2 (1.68, 1.59-1.77), Q3 (2.56, 2.34-2.80), and Q4 (4.02, 3.68-4.39) groups ( Conclusions: RFM demonstrates a significant positive association with CMD risk, exhibiting age-dependent heterogeneity, and emphasizing age-tailored interventions for CMD prevention strategies.