Greater haemodialysis exposure ('quotidian haemodialysis') has different mortality associations by patient age group

Background: Worldwide, most people requiring kidney replacement therapy receive haemodialysis (HD) three times per week. Greater HD time and/or frequency may improve survival, but implementation requires understanding potential benefits across the range of patients. Methods: Using data from the Australia and New Zealand Dialysis and Transplant Registry, we assessed whether quotidian HD (defined as >3 sessions/week and/or >5 h/session) was associated with reduced mortality in adult patients. The primary outcome of all-cause mortality was analysed by a time-varying Cox proportional hazards model with quotidian HD as the exposure of interest. Results: Of 24 138 people who received HD between 2011 and 2019, 2632 (10.9%) received quotidian HD at some stage. These patients were younger, more likely male and more likely to receive HD at home. Overall, quotidian versus standard HD was associated with a decreased risk for all-cause mortality {crude hazard ratio [HR] 0.50 [95% confidence interval (CI) 0.45-0.56]}, but an interaction between quotidian HD and age was identified (P =. 005). Stratified by age groups and splitting follow-up time where proportional hazards were violated, the corresponding HR compared with standard HD was 2.43 (95% CI 1.56-3.79) for people >75 years of age in the first year of quotidian HD, 1.52 (95% CI 0.89-2.58) for 1-3 years and 0.95 (95% CI 0.51-1.78) for ≥3 years. There was no significant survival advantage in younger people. Conclusions: Although quotidian HD conferred survival benefit in crude analyses, people ≥75 years of age had greater mortality with quotidian HD than standard HD. The mortality benefit in younger people was attenuated when adjusted for known confounders.