Estimated glucose disposal rate and incident cardiometabolic multimorbidity in two ageing cohorts from China and England: cross-national consistency and transportability.

BACKGROUND: The estimated glucose disposal rate, an insulin-resistance surrogate derived from routine variables, has been linked to cardiometabolic multimorbidity. We examined its association with cardiometabolic outcomes and cross-cohort prediction in ageing populations from China and England. METHODS: We analysed harmonized data from prospective cohorts, the China Health and Retirement Longitudinal Study and the English Longitudinal Study of Ageing. The estimated glucose disposal rate was modelled per one-standard-deviation decrease using Cox proportional-hazards models with attained age as the time scale. The primary analysis included participants free of diabetes, heart disease and stroke, and used incident heart disease or stroke as the non-glycaemic cardiovascular outcome. Cohort estimates were pooled by random-effects meta-analysis. The composite multimorbidity outcome was used for cross-cohort prediction with frozen-coefficient models. RESULTS: Lower estimated glucose disposal rate was associated with incident non-glycaemic cardiovascular disease, with hazard ratios of 1.25 (95% confidence interval 1.18-1.33) in China and 1.23 (1.14-1.32) in England; the pooled estimate was 1.24 (1.19-1.30). Findings were directionally consistent across sensitivity analyses. External concordance was 0.66-0.68, whereas absolute seven-year risk was substantially miscalibrated and improved after recalibration to local incidence. The index discriminated better than glycated haemoglobin alone but did not improve discrimination over its constituent variables. CONCLUSIONS: Lower estimated glucose disposal rate was consistently associated with incident non-glycaemic cardiovascular disease. For cardiometabolic multimorbidity, models retained cross-cohort discrimination, but absolute risk was miscalibrated before local recalibration. The index did not improve discrimination beyond its constituent variables.