The non-linear association between serum iron and severe impairment of activities of daily living in ischemic stroke patients

Objectives This study aims to explore the dose–response relationship and threshold effect of serum iron levels on severe impairment of activities of daily living (ADL) in ischemic stroke patients. Methods This cross-sectional study included 2,035 ischemic stroke patients admitted to Shanghai East Hospital from 2020 to 2022. Serum iron levels were measured upon admission, and ADL was evaluated using the Barthel Index. Restricted cubic spline regression, multivariate logistic models, and subgroup analysis were employed to analyze the dose–response relationship. Results A non-linear relationship ( p = 0.005) was observed between serum iron and severe ADL impairment, with an inflection point at 17.5 μmol/L. Below this threshold, each 1 μmol/L increase in serum iron was associated with 9% lower odds of severe ADL impairment (OR = 0.91, 95% CI: 0.876–0.946). No significant association was observed above 17.5 μmol/L ( p > 0.05). Subgroup analyses revealed no significant interactions in any subgroup. Conclusion The study found a non-linear relationship between serum iron and severe ADL impairment after ischemic stroke, with an inflection point at about 17.5 μmol/L. Future prospective studies are necessary to clarify this association.