Factors associated with improved short term survival in obese end stage renal disease patients

PURPOSE: In contrast to its role in the general population, obesity, defined as body mass index (BMI) ≥ 30 kg/m², has been associated with improved survival in patients with end stage renal disease (ESRD). This apparent benefit has not been explained. METHODS: Using the United States Renal Data System (USRDS), we performed an historical cohort study on 151,027 patients initiated on ESRD therapy between January 1, 1995 and June 30, 1997, who never received renal transplants, and who had information sufficient to calculate BMI. We explored the association of various comorbidities present at the time of dialysis initiation (from HCFA Form 2728) with the presence of obesity by logistic regression, and the association of obesity with patient survival, including specific causes of death, by Cox regression adjusting for factors known to be associated with survival in this population. RESULTS: Obese patients had an unadjusted two-year survival of 68% compared with 58% for non obese patients. Obesity was independently associated with a reduced risk of mortality among chronic dialysis patients (adjusted hazard ratio (AHR) 0.75, 95% confidence interval, 0.72-0.78), after controlling for all comorbidities and risk factors. However, there were significantly adverse interactions among whites (AHR 1.22, 1.14-1.30, across all causes of death) and females (AHR 1.12, 1.04-1.20, entirely due to an increased risk of infectious death). CONCLUSIONS: Obesity in patients presenting with ESRD is associated independently with reduced all cause mortality; however, the relationship is complex and is stronger in African Americans. In addition, subgroup analysis suggests that obesity is associated with increased risk of infectious death in females.