Association between hemoglobin level and mortality in patients undergoing maintenance hemodialysis: a nationwide dialysis registry in Japan.

Background: The optimal hemoglobin (Hb) range in patients undergoing hemodialysis remains controversial. We aimed to investigate the association between Hb levels and mortality in patients undergoing hemodialysis and explore the potential factors modifying this association.

Methods: This observational study utilized a nationwide database from the Japanese Renal Data Registry spanning from 2019 to 2021. This study included 265,779 patients undergoing hemodialysis thrice a week. The association between Hb levels and all-cause and cause-specific mortality was investigated using Cox regression analysis. The nonlinear relationship between Hb levels and outcomes was investigated using restricted cubic spline analysis.

Results: During a median follow-up period of 24 months, 45,734 patients died. Compared to the reference Hb category of 10-10.9 g/dL, the risk of all-cause mortality was higher in the Hb categories of < 9.0, 9.0-9.9, and ≥ 13 g/dL with adjusted hazard ratios (95% confidence intervals) of 1.24 (1.20-1.29), 1.09 (1.06-1.12), and 1.19 (1.14-1.25), respectively. Restricted cubic spline analysis also showed a U-shaped relationship between Hb level and mortality. The subgroup analysis indicated that the Hb category of 12.0-12.9 g/dL was associated with increased mortality risk in patients with a dialysis vintage of ≥ 10 years and those with a history of cerebral infarction.

Conclusion: Hb levels of < 10.0 and ≥ 13.0 g/dL were significantly associated with an increased mortality risk compared to an Hb level of 10.0-10.9 g/dL in patients undergoing hemodialysis.