Impact of obesity on the evolution of outcomes in peritoneal dialysis patients

Background. Some studies reveal that obesity is associated with a decrease in mortality in haemodialysis (HD) patients. However, few studies have addressed the association between body mass index (BMI) and peritoneal dialysis (PD) patients. Methods. We performed this longitudinal, retrospective study to evaluate the impact of obesity on PD patients, using data from the Catalan Registry of Renal Patients from 2002 to 2015 (n=1573). Obesity was defined as BMI >= 30; low weight: BMI<18.5; normal range: BMI = 18.5-24.99; and pre-obesity: BMI = 25-29.99 kg/m(2). Variations in BMI were calculated during follow-up. The main outcomes evaluated were the technique and patient survival. Results. Obesity was observed in 20% of patients starting PD. We did not find differences in sex or PD modality, with the obesity group being older (65.9% are >= 55years versus 59% non-obese, P=0.003) and presenting more diabetes mellitus and cardiovascular disease (CVD) (47.9% obese versus 25.1% non-obese and 41.7% versus 31.5%, respectively). We did not observe differences in haemoglobin, albumin and Kt/V in obese patients. Regarding peritonitis rate, we did not find any difference between groups, presenting more peritonitis patients on continuous ambulatory peritoneal dialysis and aged >= 65years [sub-hazard ratio (SHR) = 1.75, P=0.000 and SHR = 1.56, P=0.009]. In relation to technique survival, we found higher transfer to HD in the obese group of patients in the univariate analysis, which was not confirmed in the multivariate analysis (SHR = 1.12, P=0.4), and we did not find differences in mortality rate. In relation to being transplanted, the underweight group, elderly and patients with CVD or diabetic nephropathy presented less probability to undergo kidney transplantation (SHR = 0.65, 0.24, 0.5 and 0.54, P<0.05). Obese patients did not present differences in survival with weight changes but in normal-weight patients, a gain of 7% of the basal weight during the first year had a protective effect on death risk (hazard ratio 0.6, P=0.034). Conclusions. Obese and non-obese patients starting on PD had similar outcomes.