Survival differences between peritoneal dialysis and hemodialysis among "large" ESRD patients in the United States

Background. It has been hypothesized that peritoneal dialysis compared to hemodialysis may be less effective in large patients with end-stage renal disease (ESRD). Methods. We tested this hypothesis in a cohort of 134,728 new ESRD patients who were initiated on dialysis from May 1, 1995 to July 31, 1997 using data from United States Renal Data System (USRDS). Cox regression models evaluated the association of body mass index (BMI) in quintiles (8.8-20.9, 20.9-23.5, 23.5-26.1, 26.1.-30.0, 30.0-75.2 kg/m(2)) with mortality over 2 years in peritoneal dialysis and hemodialysis patients separately, while time-dependent models evaluated the relative risk (RR) of death by modality for each BMI quintile. Results. For hemodialysis, the adjusted RR of death was greatest for patients with BMI <20.9 (RR=1.40, 95% CI 1.32-1.50 for diabetics and RR=1.27, 95% CI 1.21-1.34 for nondiabetics) and lowest for patients with BMI >30.0 (RR=0.97, 95% CI 0.96-0.99 for diabetic and RR=0.97, 95% CI 0.95-0.98 for nondiabetic patients) compared with the referent (23.5-26.1; RR=1.00). For peritoneal dialysis, the RR of death was also higher for patients with a BMI <20.9 (RR=1.20,95% CI 1.00-1.43 for diabetic and RR=1.39, 95% CI 1.19=1.64 for nondiabetic patients) but no survival advantage was associated with higher BMI values. The RR of death (peritoneal dialysis/hemodialysis) for each BMI quintile was 0.99,1.12,1.26 (P<0.01), 1.15 (P<0.01), and 1.44 (P<0.0001) for diabetic and were 1.07, 1.01, 0.96, 1.04, and 1.22 (P<0.01) for nondiabetic patients, respectively. Conclusion. We conclude that body size modifies the impact of dialysis modality on mortality risk among new ESRD patients in the United States. The selection of hemodialysis over peritoneal dialysis was associated with a survival advantage in patients with large body habitus.