Combined Effects of Nutritional and Inflammatory Status on Erythropoiesis Resistance: A Longitudinal Patient-Month Analysis in Hemodialysis Patients

Background: Nutritional status and inflammation are thought to influence erythropoiesis in hemodialysis patients, but their combined effects on erythropoiesis resistance index (ERI) have not been well characterized in longitudinal settings. Methods: We conducted a retrospective longitudinal study of 57 maintenance hemodialysis patients (684 patient-month observations) between January and December 2025. ERI was analyzed using mixed-effects models with serum albumin and C-reactive protein (CRP) as markers of nutritional status and inflammation. Both continuous models and categorical analyses, including a cumulative nutritional–inflammatory risk score, were performed. Results: Lower albumin was significantly associated with higher ERI, whereas CRP was not independently associated. The interaction between albumin and CRP was not statistically significant. In contrast, the cumulative nutritional–inflammatory risk score showed a graded association with ERI, which remained significant after adjustment for iron-related parameters. Sensitivity analyses restricted to ESA-treated patient-months yielded similar results. Conclusions: In maintenance hemodialysis patients, nutritional and inflammatory status are additively associated with ERI. Although no statistically significant interaction was observed, the cumulative burden of these factors may contribute to variability in ESA responsiveness. These findings support a longitudinal, individualized approach to anemia management.