Longitudinal Trajectories of Body Roundness Index and Risk of Incident Hypertension in Non-Diabetic Elderly Adults: A Prospective Nationwide Cohort Study Involving Two Cohorts.

BACKGROUND: Central adiposity is a key determinant of hypertension, yet most studies rely on single-time-point measures or include individuals with diabetes, potentially confounding associations. The relationship between long-term body roundness index (BRI) trajectories and incident hypertension in non-diabetic populations remains unclear. METHODS: We conducted a longitudinal analysis of non-diabetic middle-aged and older adults from the China Health and Retirement Longitudinal Study (CHARLS), with external validation using the English Longitudinal Study of Ageing (ELSA). In CHARLS, BRI measurements from Waves 1-3 (2011-2016) were used to construct trajectories, and incident hypertension was assessed at Wave 4 (2018-2020). In ELSA, trajectories were constructed using BRI measurements from Waves 2, 4, and 6 (2004-2013), and incident hypertension was assessed at Wave 8 (2016-2017). Associations were examined using multivariable logistic regression, with subgroup and sensitivity analyses. Machine learning models were additionally developed for multivariable hypertension risk prediction. RESULTS: Three BRI trajectories were identified in both cohorts: low-level inverted U-shaped, moderate-level inverted U-shaped, and high-level increasing trajectories. Higher BRI trajectories were associated with a graded increase in incident hypertension risk in CHARLS. Compared with the low-level inverted U-shaped trajectory, the adjusted odds ratios (95% confidence intervals) were 1.40 (1.13-1.73) for the moderate-level inverted U-shaped trajectory and 1.76 (1.21-2.56) for the high-level increasing trajectory. Directionally consistent findings were observed in ELSA, particularly for the high-level increasing trajectory. Findings remained robust in subgroup and sensitivity analyses. Machine learning analyses showed that BRI trajectory provided complementary predictive information when combined with clinical and biomarker variables. CONCLUSIONS: Longitudinal BRI patterns were associated with incident hypertension in non-diabetic adults. Repeated assessment of BRI may provide complementary information for identifying individuals at elevated hypertension risk, although its causal and clinical implications require further investigation.