Background A higher body mass index (BMI) has been associated with better survival among chronic kidney disease patients in some reports. However, more research is required to determine the associations between BMI and mortality in incident hemodialysis patients. Therefore, this study aimed to investigate the association between mortality and BMI measured at the first hemodialysis session and 2 weeks after hemodialysis initiation in Japanese patients with incident hemodialysis. Methods We retrospectively enrolled 266 adult patients with incident hemodialysis who were treated at our hospital between May 2013 and June 2019. The data on BMI was obtained at the first hemodialysis session and 2 weeks after hemodialysis initiation. Patients were divided into tertiles based on BMI [2]. The normal group was used as the reference group. The primary outcome was all-cause mortality. Results The mean age of patient was 68.9 ± 12.0 years, and the BMI was 23.3 ± 4.24 kg/m2 at the first hemodialysis session. The body mass index was 22.0 ± 3.80 kg/m2 at 2 weeks after hemodialysis initiation. During a mean follow-up of 3.89 ± 2.12 years, 80 (30.1%) deaths occurred. In multivariate analyses, low BMI at the first hemodialysis session was significantly associated with worse all-cause mortality (hazard ratio, 2.39; 95% confidence interval, 1.13–5.03). At 2 weeks after hemodialysis initiation, high BMI was significantly associated with better all-cause mortality (hazard ratio, 0.38; 95% confidence interval, 0.18–0.81). Conclusion At 2 weeks after HD initiation, high BMI was associated with lower mortality in Japanese patients with incident hemodialysis.
