Supplementary Material for: Association between timing of vascular access creation and mortality in patients initiating hemodialysis: A nationwide cohort study in Japan

Introduction: The optimal time for vascular access (VA) creation remains controversial. Methods: We conducted a cohort study using data from the Japanese Society for Dialysis Therapy Renal Data Registry. Adult patients who started receiving hemodialysis in 2007 and had a permanent VA created were included. The exposure of interest was the timing of VA creation, categorized into three groups: early VA creation (defined as creation at least 4 months before hemodialysis initiation), just prior VA creation (creation between 1 and 3 months before hemodialysis initiation), and late VA creation (creation within 1 month of or after hemodialysis initiation). Cox regression analyses were used to compare 1-year all-cause mortality, with late VA creation as the reference group. Owing to the violations of the proportional hazards assumptions, the follow-up period was divided into ‘early’ (1–4 months follow-up) and ‘late’ (5–12 months follow-up) periods. Results: Overall, 1,280 (15.4%) of 8,322 patients died. Both early creation and just prior creation were associated with lower all-cause mortality in the early period compared with late creation. In the late period, the hazard ratios (HRs) for all-cause mortality decreased with earlier VA creation (adjusted HRs [95% confidence intervals]: 0.49 [0.35–0.67] for the early creation group and 0.63 [0.51–0.79] for the just prior creation group). Conclusion: Our study suggests that VA creation at least 1 month before hemodialysis initiation is associated with lower all-cause mortality in the early period, with earlier VA creation resulting in further mortality reduction in the late period.