Combination of once-weekly haemodialysis with peritoneal dialysis is associated with lower mortality compared with peritoneal dialysis alone: a longitudinal study

Background Approximately 20% of patients on peritoneal dialysis (PD) in Japan are on combination with once-weekly haemodialysis (HD). This study aimed to compare outcomes of combination therapy and PD alone. Methods This longitudinal study on the Japanese Renal Data Registry included patients on PD from 2010 to 2014. Subjects were followed until the end of 2015. Exposure of interest was combination therapy compared with PD alone. Outcomes were complete transition to HD, all-cause mortality, cardiovascular (CV) mortality and congestive heart failure (CHF)-related mortality. Patients who initiated combination therapy were matched with those on PD alone by propensity scores. Data were analysed using Cox regression models. Results Among the matched cohort, 608 patients were on combination therapy and 869 were on PD alone. Decline in body weight and residual renal function was more prominent in the combination therapy group. During a median follow-up of 2.5 years, 224 deaths occurred. All-cause mortality {hazard ratio (HR) [95% confidence interval (CI)] 0.56 (0.42-0.75)}, CV mortality [HR 0.48 (0.32-0.72)] and CHF-related mortality [HR 0.19 (0.07-0.55)] were significantly lower, but complete transition to HD was significantly earlier [HR 1.72 (1.45-2.03)] in the combination therapy group. Sensitivity analyses considering the effects of dialysis facilities yielded similar results. Assuming causality, numbers needed to treat to prevent one death per year were 34 patients. Conclusions Combination therapy was associated with lower all-cause mortality, CV mortality and CHF-related mortality, but earlier transition to HD compared with PD alone, which might be due to better fluid removal by HD.