Survival Advantage in Black Versus White Men With CKD: Effect of Estimated GFR and Case Mix

Background: Black dialysis patients have significantly lower mortality compared with white patients, in contradistinction to the higher mortality seen in blacks in the general population. It is unclear whether a similar paradox exists in patients with non-dialysis-dependent chronic kidney disease (CKD), and if it does, what its underlying reasons are. Study Design: Historical cohort. Setting & Participants: 518,406 white and 52,402 black male US veterans with non-dialysis-dependent CKD stages 3-5. Predictor: Black race. Outcomes & Measurements: We examined overall and CKD stage-specific all-cause mortality using parametric survival models. The effect of sociodemographic characteristics, comorbid conditions, and laboratory characteristics on the observed differences was explored in multivariable models. Results: During a median follow-up of 4.7 years, 172,093 patients died (mortality rate, 71.0 [95% CI, 70.6-71.3] per 1,000 patient-years). Black race was associated with significantly lower crude mortality (HR, 0.95; 95% CI, 0.94-0.97; P < 0.001). The survival advantage was attenuated after adjustment for age (HR, 1.14; 95% CI, 1.12-1.16), but was magnified after full multivariable adjustment (HR, 0.72; 95% CI, 0.70-0.73; P < 0.001). The unadjusted survival advantage of blacks was more prominent in those with more advanced stages of CKD, but CKD stage-specific differences were attenuated by multivariable adjustment. Limitations: Exclusively male patients. Conclusions: Black patients with CKD have lower mortality compared with white patients. The survival advantage seen in blacks is accentuated in patients with more advanced stages of CKD, which may be explained by changes in case-mix and laboratory characteristics occurring during the course of kidney disease.