Objective To investigate the expression levels of serum microRNA-21(miR-21)and microRNA-23a(miR-23a)in patients with Parkinson's disease(PD)and their correlations with cognitive function and inflammatory responses.Methods A total of 120 PD patients admitted to the Second Affiliated Hospital of Hebei North University between December 2019 and January 2022 were enrolled,along with 115 healthy controls from the same period.Serum miR-21 and miR-23a levels were measured by quantitative real-time PCR,while serum levels of IL-6,CRP,and TNF-α were determined by ELISA.According to Mini-Mental State Examination(MMSE)scores,PD patients were classified into a cognitive impairment group(MMSE<26,n=72)and a normal cognition group(MMSE≥26,n=48).General characteristics in clinical and biochemical indicators levels were compared between the two groups.Spearman correlation analysis was used to assess the relationships of miRNAs and MMSE scores.Multivariate logistic regression analysis was employed to identify risk factors for cognitive impairment.The predictive value of miR-21 and miR-23a was evaluated using Receiver Operating Characteristic(ROC)curve analysis.Results Serum miR-21,miR-23a,IL-6,CRP,and TNF-α levels were significantly higher in the PD group than in the control group(P<0.01).The cognitive impairment group showed higher levels of miR-21,miR-23a,and inflammatory factor than the cognitively normal group(P<0.01).Correlation analysis revealed that miR-21 and miR-23a levels were negatively correlated with MMSE scores(r=-0.472,-0.514;P<0.001)and positively correlated with IL-6,CRP,and TNF-α(P<0.001).Multivariate Logistic regression analysis revealed that high expression of miR-21,miR-23a,and a higher UPDRS score,were independent risk factors for cognitive impairment in PD patients(P<0.05).Combined detection of miR-21 and miR-23a showed higher predictive accuracy for cognitive impairment than either marker alone(P<0.05).Conclusion Serum expression levels of miR-21 and miR-23a was upregulated in PD patients,which were associated with cognitive function and inflammatory response.Combined detection shows good predictive value for cognitive impairment..