Objective To explore the changes in the expression of interferon regulatory factor 8(IRF8),a factor regulating macrophage polarization,in stroke rehabilitation and its relationship with cognitive function recovery.Methods This cross-sectional retrospective study included a cohort of patients with acute ischemic stroke treated in our hospital from January 2021 to January 2023.According to the Mini-Mental State Examination score two weeks after stroke,they were divided into post-stroke cognitive impairment(PSCI)group(n=76)and non-PSCI group(n=42).The expres-sion of the IRF8 gene in peripheral blood mononuclear cell(PBMC)was determined using RT-qPCR.The relationship be-tween IRF8 gene expression and cognitive function was studied by a binary logistic regression analysis.Results The ex-pression of IRF8 mRNA in PBMCs in the PSCI group was significantly higher than that in the non-PSCI group(P<0.001).There were significant differences in the proportions of PSCI and non-PSCI patients in the three groups by IRF8 mRNA ter-tiles[T1:53.8%(21/39),T2:64.1%(25/39),T3:75.0%(30/40),χ2=8.082,P=0.018].The logistic regression analy-sis showed that the IRF8 mRNA level>0.024(OR=1.956,P<0.001),age(OR=1.062,P<0.001),National Institutes of Health Stroke Scale(NIHSS)score(OR=1.145,P=0.014),and hemoglobin(OR=1.194,P=0.024)were significantly associated with a higher risk of PSCI.When the cut-off value was 0.01,the area under the curve(AUC)for IRF8 mRNA predicting PSCI was 0.682,with an accuracy of 71.49%,a specificity of 50.24%,and a sensitivity of 71.42%.Including IRF8 mRNA,age,NIHSS score,and hemoglobin into the nomogram,the AUC for PSCI prediction was 0.862.Conclusion The expression of IRF8 mRNA in PBMCs at admission is associated with the development of PSCI in the acute phase of stroke.