Association of race and age with survival among patients undergoing dialysis

Context: Many studies have reported that black individuals undergoing dialysis survive longer than those who are white. This observation is paradoxical given racial disparities in access to and quality of care, and is inconsistent with observed lower survival among black patients with chronic kidney disease. We hypothesized that age and the competing risk of transplantation modify survival differences by race. Objective: To estimate death among dialysis patients by race, accounting for age as an effect modifier and kidney transplantation as a competing risk. Design, Setting, and Participants: An observational cohort study of 1 330 007 incident end-stage renal disease patients as captured in the United States Renal Data System between January 1, 1995, and September 28, 2009 (median potential follow- up time, 6.7 years; range, 1 day-14.8 years). Multivariate age-stratified Cox proportional hazards and competing risk models were constructed to examine death in patients who receive dialysis. Main Outcome Measures: Death in black vs white patients who receive dialysis. Results: Similar to previous studies, black patients undergoing dialysis had a lower death rate compared with white patients (232 361 deaths [57.1% mortality] vs 585 792 deaths [63.5% mortality], respectively; adjusted hazard ratio [aHR], 0.84; 95% confidence interval [CI], 0.83-0.84; P<.001). However, when stratifying by age and treating kidney transplantation as a competing risk, black patients had significantly higher mortality than their white counterparts at ages 18 to 30 years (27.6% mortality vs 14.2%; aHR, 1.93; 95% CI, 1.84-2.03), 31 to 40 years (37.4% mortality vs 26.8%; aHR, 1.46; 95% CI, 1.41-1.50), and 41 to 50 years (44.8% mortality vs 38.0%; aHR, 1.12; 95% CI, 1.10-1.14; P<.001 for interaction terms between race and each afore-mentioned age category), as opposed to patients aged 51 to 60 years (51.5% vs 50.9%; aHR, 0.93; 95% CI, 0.92-0.94), 61 to 70 years (64.9% vs 67.2%; aHR, 0.87; 95% CI, 0.86-0.88), 71 to 80 years (76.1% vs 79.7%; aHR, 0.85; 95% CI, 0.84-0.86), and older than 80 years (82.4% vs 83.6%; aHR, 0.87; 95% CI, 0.85-0.88). Conclusions: Overall, among dialysis patients in the United States, there was a lower risk of death for black patients compared with their white counterparts. However, the commonly cited survival advantage for black dialysis patients applies only to older adults, and those younger than 50 years have a higher risk of death.