Introduction: End-stage kidney disease patients have increased mortality compared to the general population. Haemodialysis (HD) of more frequent and of longer duration has been proposed to improve survival but it remains unclear if this is attributed to increased frequency, duration, or both. We aimed to examine the independent effects of session frequency and duration on mortality in incident HD patients.

Methods: A retrospective cohort study was performed using data from the Australian and New Zealand Dialysis and Transplant Registry examining non-Indigenous patients aged ≥18 years who initiated HD of ≥3 sessions/week in Australia from 2001 to 2015. Initial dialysis prescription was categorized as session duration >5 h/session compared to ≤5 h/session and session frequency as >3 sessions/week compared to 3 sessions/week. Survival analysis was performed using Cox regression analysis, with multivariable analysis controlling for available covariates.

Results: We examined 16 944 patients of whom 757 (4.5%) received >3 sessions/week and 518 (3.1%) received >5 h/session. After controlling for frequency, patients initiated on HD sessions >5 h had a significantly reduced risk of mortality compared with patients with HD session ≤5 h (adjusted hazard ratio (HR) = 0.57; 95% confidence interval (CI) = 0.44-0.74). In contrast, patients initiated on >3 sessions/week of HD had a similar risk of death when compared with patients on 3 sessions/week of HD (adjusted HR = 0.97; 95% CI = 0.84-1.13), after controlling for duration. Limitations include potential residual confounding and changes in exposure over time.

Conclusions: Longer duration rather than increased frequency of treatment appears to reduce mortality in HD patients. This has implications for management and requires further study.