Body size and outcomes on peritoneal dialysis in the United States

Background. Being overweight is often cited as a relative contraindication to peritoneal dialysis. Our primary objective was to determine whether actual mortality rates support this opinion. Methods. Retrospective cohort study of United States Medicare patients initiating dialysis between 1995 and 2000 (N = 418,021; 11% peritoneal dialysis). Results. Seven percent were underweight [body mass index (BMI) < 18.5 kg/m(2)], 27% were overweight (BMI 25.0 to 29.9 kg/m(2)), and 23% were obese (BMI> 29.9 kg/m(2)) at dialysis initiation. Compared to those with normal BMI, the adjusted odds of initiating peritoneal dialysis were 0.70 (P < 0.05) in underweight, 1.12 (P < 0.05) in overweight, and 0.87 (P < 0.05) in obese subjects. Among peritoneal dialysis patients, adjusted mortality hazard ratios in the first, second, and third year were 1.45 (P < 0.05), 1.28 (P < 0.05), and 1.17 for the underweight, respectively; 0.84 (P < 0.05), 0.89 (P < 0.05), and 0.98 for the overweight, respectively; and 0.89 (P < 0.05), 0.99, and 1.00 for the obese, respectively. Apart from higher third-year mortality in the obese, associations were similar after censoring at a switch to hemodialysis. For transplantation, the corresponding results were 0.76 (P < 0.05), 0.90 (P < 0.05), and 0.88 for the underweight, respectively; 0.95, 1.06, and 0.93 for the overweight, respectively; and 0.62 (P < 0.05), 0.68, and 0.71 for the obese, respectively. For switching to hemodialysis, hazards ratios were 0.92, 0.97, and 0.80 for the underweight, respectively; 1.07, 1.11 (P < 0.05), and 1.03 for the overweight, respectively; and 1.28 (P < 0.05), 1.29 (P < 0.05), and 1.36 (P < 0.05) for the obese, respectively. Conclusion. Although less likely to initiate peritoneal dialysis, overweight and obese peritoneal dialysis patients have longer survival than those with lower BMI, not adequately explained by lower transplantation and technique survival rates.