Body roundness index and the incidence of kidney disease: A prospective cohort study from the China Health and Retirement Longitudinal Study.

Kidney disease (KD) poses a growing global health burden, with obesity contributing to its development. The body roundness index (BRI), a novel anthropometric measure reflecting visceral adiposity, may better predict KD risk than body mass index, but longitudinal evidence is limited. In this prospective cohort study, we analyzed 8401 adults aged ≥ 45 years from the China Health and Retirement Longitudinal Study, free of KD at baseline. BRI was calculated from waist circumference and height. Incident KD was ascertained via physician-diagnosed questionnaires during 4 follow-ups (2013-2020). Cox proportional-hazards models were used to compute hazard ratios (HRs) and 95% confidence intervals (95% CIs), with adjustment for multiple covariates. Dose-response relationships were evaluated using restricted cubic splines and 2-piecewise linear regression, with subgroup analyses performed to examine effect modification. During follow-up, higher BRI was significantly associated with an increased risk of incident KD (HR = 1.10; 95% CI: 1.02-1.19; P = .017). Participants in the highest BRI quartile had a 47% greater risk compared with the lowest quartile (HR = 1.47; 95% CI: 1.06-2.05; P = .022), with a significant dose-response trend (P for trend = .014). Restricted cubic spline analysis revealed a significant overall association (P overall = .037) without evidence of nonlinearity (P nonlinearity = .307) and a meaningful inflection point (P for likelihood ratio test = 0.378). Subgroup analyses demonstrated generally consistent associations, with a significant interaction observed for dyslipidemia status (P for interaction = .037). In middle-aged and older Chinese adults, higher BRI independently predicts incident KD in a linear dose-response manner. BRI, as a simple and noninvasive measure of body fat distribution, may serve as a practical tool for early identification of individuals at elevated KD risk, supporting strategies targeting central adiposity in KD prevention.