Trajectories of kidney function decline in young black and white adults with preserved GFR: Results from the coronary artery risk development in young adults (CARDIA) study

Background: Strong racial discrepancies in end-stage renal disease exist. Whether there are race differences in kidney function loss in younger healthy persons is not well established. Study Design: Longitudinal. Setting & Participants: 3,348 black and white adults with at least 2 measurements of cystatin C-based estimated glomerular filtration rate (eGFR_cys) at scheduled Coronary Artery Risk Development in Young Adults (CARDIA) examinations (years 10, 15, and 20). Predictor: Race. Outcomes & Measurements: We used linear mixed models to examine race differences in annualized rates of eGFR _cys decline, adjusting for age, sex, lifetime exposure to systolic blood pressure >120 mm Hg, diabetes, and albumin-creatinine ratio. We used Poisson regression to compare racial differences in rapid decline (eGFR _cys decline >3% per year) by study period (10-15 years after baseline examination [defining period 1] and >15-20 years after baseline examination [defining period 2]). Results: Mean age was 35 ± 3.6 (SD) years, and mean eGFR_cys was 110 ± 20 mL/min/1.73 m² for blacks and 104 ± 17 mL/min/1.73 m² for whites at baseline. For both blacks and whites, eGFR_cys decline was minimal at younger ages (<35 years) and eGFR_cys loss accelerated at older ages. However, acceleration of eGFR_cys decline occurred at earlier ages for blacks than whites. Blacks had somewhat faster annualized rates of decline compared with whites, but differences were attenuated after adjustment in period 1 (0.13 mL/min/1.73 m² per year faster; P = 0.2). In contrast, during period 2, blacks had significantly faster annualized rates of decline, even after adjustment (0.32 mL/min/1.73 m² per year faster; P = 0.003). The prevalence of rapid decline was significantly higher for blacks versus whites, with prevalence rate ratios of 1.31 (95% CI, 1.04-1.63) for period 1 and 1.24 (95% CI, 1.09-1.41) for period 2. Differences were attenuated after full adjustment: adjusted prevalence rate ratios were 1.20 (95% CI, 0.95-1.49) for period 1 and 1.10 (95% CI, 0.96-1.26) for period 2. Limitations: No measured GFR. Conclusions: eGFR_cys decline differs by race at early ages, with faster annualized rates of decline for blacks. Future studies are required to explain the observed differences.