Association of Eosinophil Counts and Ratios With Clinical Outcomes After Acute Ischemic Stroke

Background Evidence links eosinopenia to poor 3‐month outcomes after stroke, but its long‐term prognostic value in acute ischemic cerebrovascular events remains unclear. This study aimed to evaluate the association between eosinophil counts (and ratios) and 5‐year clinical outcomes in patients with acute ischemic stroke or transient ischemic attack (TIA). Methods We analyzed data from the Third China National Stroke Registry (CNSR‐III). Patients with acute ischemic stroke or TIA were categorized into quartiles based on eosinophil counts and ratios measured within 24 h of admission. Using the highest quartile as the reference, we calculated hazard ratios (HRs) or odds ratios (ORs) with 95% confidence intervals (CIs) for adverse outcomes. The association of eosinophil levels with 5‐year risks of stroke recurrence, poor functional outcome, all‐cause death, and composite vascular events was evaluated. Results A total of 12,745 participants were enrolled. Compared to the fourth quartile of eosinophil counts, the first quartile were associated with an increased risk of stroke recurrence (adjusted hazard ratio [HR] = 1.25, 95% confidence interval [CI]: 1.10–1.41) and ischemic stroke recurrence (adjusted HR, 1.25; 95% CI: 1.10–1.42). Similar associations were observed over 5 years for poor functional outcome (adjusted odds ratio [OR] = 1.57, 95% CI: 1.40–1.76), composite vascular events (adjusted HR = 1.15, 95% CI: 1.02–1.29), and all‐cause death (adjusted HR = 1.53, 95% CI: 1.32–1.77). Parallel results were found for eosinophil ratios. Conclusions This study demonstrated that low levels of both eosinophil counts and eosinophil ratios were associated with an increased risk of adverse clinical outcomes at 5 years of follow‐up in patients with ischemic stroke or TIA.