Association between pre-stroke anemia and risk of acute kidney injury following ischemic stroke: A multi-institutional retrospective cohort study

Although anemia is an established risk factor for acute kidney injury (AKI), its specific impact on post-stroke AKI remains inadequately explored. This study aimed to investigate the association between pre-stroke anemia and the risk of developing AKI after acute ischemic stroke. This retrospective study, using the TriNetX research network database, identified adult patients who experienced their 1st recorded ischemic stroke between January 2010 and December 2023. Patients were categorized based on hemoglobin levels within 3 months pre-stroke: anemia (hemoglobin ≥8.0 and <12.0 g/dL) versus control (hemoglobin ≥12.0 g/dL). After 1:1 propensity score matching, we analyzed the outcomes at 1-year follow-up. The primary endpoint was the development of AKI during the follow-up period. Secondary endpoints comprised all-cause mortality, pneumonia, and intensive care unit admission. After propensity score matching, 61,896 patients were included in each cohort. Patients with pre-stroke anemia had a significantly higher 1-year risk of AKI (hazard ratio [HR]: 1.89, 95% confidence interval [CI]: 1.83-1.96), mortality (HR: 1.86, 95% CI: 1.80-1.93), pneumonia (HR: 1.76, 95% CI: 1.69-1.84), and intensive care unit admission (HR: 1.60, 95% CI: 1.55-1.65) compared to controls (all P < .001). A graded association was observed between increasing anemia severity and adverse outcomes. The findings remained robust across sensitivity and subgroup analyses. Pre-stroke anemia is associated with an increased risk of post-stroke AKI and other adverse outcomes. However, given the observational nature of this study, future prospective studies are warranted to confirm these findings and elucidate the underlying mechanisms.