Comparative effects of central adiposity and BMI trajectories on cardiometabolic diseases in Chinese adults: a longitudinal cohort study

Whether long-term trajectories of central adiposity indices predict cardiometabolic diseases better than BMI remains uncertain. We compared trajectories of central adiposity indices and BMI in relation to cardiometabolic outcomes and estimated potential population benefits from trajectory improvement. Among 4,295 adults from the China Health and Retirement Longitudinal Study, group-based trajectory modeling identified three trajectories for each obesity index. BMI, waist circumference (WC), waist-to-height ratio (WHtR), and body roundness index (BRI) showed Low-stable, Moderate-stable, and High-stable patterns, whereas the high ABSI (a body shape index) group followed a High-to-low pattern. Cox models examined associations with incident diabetes, heart disease, stroke, and cardiometabolic multimorbidity (CMM) between 2015 and 2020. Δβ bootstrap tests compared association strength across indices, and two one-sided tests (TOST) assessed equivalence within ± 10–15%. Population impact fractions (PIFs) estimated preventable events under counterfactual trajectory-shift scenarios. During follow-up, 379 diabetes, 458 heart disease, 252 stroke, and 84 CMM events occurred. Compared with the Low-stable group, the High-stable groups of BMI, WC, WHtR, and BRI were associated with higher risks of all outcomes, with hazard ratios of approximately 2.7–3.5 for diabetes and broadly elevated risks for heart disease, stroke, and CMM, whereas ABSI showed no significant associations. Δβ contrasts indicated that WHtR and BRI had significantly stronger associations with diabetes than BMI and WC, while differences among indices for heart disease and stroke were small and often within TOST equivalence margins. Under the realistic partial-shift scenario, PIFs suggested that improving trajectories could avert about 6% of diabetes cases and 4–7% of CMM events, with smaller but meaningful reductions in heart disease and stroke. Central adiposity indices, particularly WHtR and BRI, demonstrated favorable trajectory-based discrimination for diabetes, whereas differences among anthropometric measures were modest for cardiovascular outcomes. These findings support an outcome-specific and context-sensitive approach to adiposity assessment.