Abstract 044: Cardiorespiratory Fitness May Explain a Proportion of Observed Racial Disparity in Incident Chronic Kidney Disease over 30 Years: Results From the CARDIA Study

Abstract

Introduction: Racial and ethnic minorities are at higher risk for Chronic Kidney Disease (CKD). Higher levels of cardiorespiratory fitness (CRF) can reduce the risk of a rapid decline in estimated glomerular filtration rate (eGFR) and incidence of CKD. Little is known regarding how CRF contributes to racial disparities in CKD. Hypotheses: We hypothesized that: 1) baseline CRF is inversely associated with the risk of incident CKD after adjustment for covariates and 2) differences in baseline CRF account for a proportion of the disparity in incident CKD between blacks and whites. Methods: A total of 4328 young adults without CKD (age 24.8±3.6 years, 52.8% (n=2285) women, 51.9% (n=2247 black) completed a maximal graded treadmill test at baseline. We calculated eGFR using the CKD-EPI formula (baseline eGFR: 102.1±17.9 and 92.3±14.1 mL/minute/1.73 m 2 for blacks and whites, respectively). We defined CKD status as eGFR of <60 mL/minute/1.73 m 2 during 10, 15, 20, 25, and 30 year follow-up assessments. Multivariable Cox models examined hazard ratios (HR) and 95% confidence intervals (CI) for incidence of CKD. Models adjusted for baseline race, sex, age, field center, alcohol intake, smoking status, healthy eating index, eGFR, maximal educational attainment, and time-varying BMI, diabetes, and hypertension. The percent reduction in parameter estimates determined the excess risk explained according to CRF. Results: During the 30 years of follow-up, 84 blacks and 43 whites developed CKD. Every 1-minute lower treadmill duration associated with 12% higher rate of CKD (HR=1.12 (1.01-1.22)). Blacks were 1.89 times more likely to develop CKD compared to whites (HR=1.89 (1.23-2.91)). This was reduced to 1.75 (1.13-2.70) with CRF added to the model. This corresponds to a β reduction of 14.3% for race according to CRF. Conclusion: Both low fitness during young adulthood and black race are associated with higher incidence of CKD later in life. Fitness is a modifiable factor that could be targeted to address a portion of the disparity gap in CKD.