Seasonal differences in cardiac prognosis in incident hemodialysis patients: a finding from Japanese multicenter dialysis cohort study

Background: The initiation of hemodialysis exhibits winter-peak seasonal variations, possibly associated with increased cardiac events during winter. The season of cardiac disease onset affects prognosis; however, the relationship between the season of hemodialysis initiation and subsequent cardiac outcomes remains unclear. We aimed to evaluate this association to determine whether the season of hemodialysis initiation could influence subsequent cardiac events. Methods: We used data from a Japanese multicenter prospective dialysis initiation cohort. We divided the patients into four groups based on the season of hemodialysis initiation: Spring, Summer, Autumn, and Winter. The outcome was 3-year cardiac events defined as a composite of ischemic heart disease, heart failure, and sudden death. Considering the competing risks, we compared the incidence of subsequent cardiac events with the hemodialysis initiation season. Results: Among the 1396 eligible patients, hemodialysis was initiated in 402 (29%), 346 (25%), 270 (19%), and 378 (27%) patients in Spring, Summer, Autumn, and Winter, respectively. Total fluid removal, heart failure symptoms, and fluid overload during the first hemodialysis session were more frequent in Autumn and Winter. During the 3-year follow-up, 264 patients (19%) developed cardiac events. Autumn was associated with a higher risk of developing cardiac events than Summer. Compared with Summer, the adjusted subdistribution hazard ratios (95% confidence intervals) were 1.40 (0.97–2.02) in Spring, 1.50 (1.02–2.21) in Autumn, and 1.15 (0.80–1.67) in Winter. Conclusion: Hemodialysis initiation in autumn may be a potential indicator of subsequent cardiac events. Further studies are required to elucidate the underlying pathophysiological mechanisms.