Objective To explore the diagnostic value of serum neuronal Per-Arnt-Sim domain protein 4(NPASDP-4)and myelin basic protein(MBP)expression in patients with Parkinson's disease in relation to cognitive impairment(CI)and severity.Methods Selected and 138 Parkinson's disease patients admitted to the 909th Hospital of the Joint Logistics Support Force of the People's Liberation Army of China as the Parkinson's disease group,and 69 healthy people in the physical examination center of the hospital were in the healthy control group.Patients with Parkinson's disease were divided into normal cognitive function group(n=55),mild CI group(n=51)and dementia group(n=32)according to whether CI occurred and its severity.General data of subjects was collected,the serum levels of NPASDP-4 and MBP were detected by ELISA,correlation analysis was adopted by Spearman rank correlation or Pearson linear correlation,diagnostic value was analyzed by ROC curve,and influencing factors were analyzed by multivariate Logistic regression.Results Compared with the healthy control group,the levels of serum NPASDP-4(6.75±0.48 ng/ml vs 2.38±0.31 ng/ml)and MBP(8.34±0.65 μg/L vs 3.54±0.42 μg/L)in the Parkinson's disease group were increased with statistical significance(r=68.751,55.761,all P＜0.05).There were significant differences in H-Y stage among the normal cognitive function group,mild CI group and dementia group(x2=7.788,P＜0.05).Compared with the group with normal cognitive function(47.92±11.63 score),the mild CI group(50.78±13.69 score)and the dementia group(41.95±10.36 score)showed an increase in UPDRS-Ⅲ scores,and the differences were statistically significant(H=6.672,all P＜0.05).In normal cognitive function group,mild CI group and dementia group,the course of disease,and serum NPASDP-4(5.89±0.40,6.83±0.55,8.12±0.54 ng/ml)and MBP(6.65±0.56,8.94±0.69,10.27±0.70μg/L)levels were significantly increased(H=207.950,355.594,allP＜0.05),while MMSE score(28.47±0.94,24.51±1.35,17.09±2.57 score),MoCA score(27.45±1.03,20.18±1.92,11.75±2.53 score)and GPCOG total score(13.47±0.69,10.25±1.04,8.97±0.82 score)were significantly decreased,and the differences were statistically significant(H=515.005,775.933,327.584,all P＜0.05),respectively.The serum levels of NPASDP-4 and MBP in Parkinson's disease patients were significantly positively correlated with the course of disease(r=0.316,0.358),H-Y stage(r=0.345,0.384)and UPDRS-Ⅲ score(r=0.371,0.396),and significantly negatively correlated with MMSE score(r=-0.468,-0.517),MoCA score(r=-0.504,-0.569)and GPCOG total score(r=-0.527,-0.538)(all P＜0.05),respectivey.The areas under the curve(AUC)of the serum levels of NPASDP-4,MBP and their combination in diagnosing of Parkinson's disease were 0.850,0.930 and 0.960,respectively.The AUC of the serum levels of NPASDP-4 and MBP and their combination in diagnosing the severity of CI in patients with Parkinson's disease were 0.866,0.803 and 0.933,respectively.H-Y stage metaphase[OR(95％CI):4.725(1.742～12.814)],H-Y stage advanced[OR(95％CI):5.083(1.919～13.464)],UPDRS-Ⅲ score[OR(95％CI):3.257(1.464～7.246)],NPASDP-4[OR(95％CI):5.324(1.516～18.701)]and MBP[OR(95％CI):5.769(2.459～13.533)]were the influential factors for CI in patients with Parkinson's disease(all P＜0.05).NPASDP-4[OR(95％CI):4.768(2.382～9.543)]and MBP[OR(95％CI);5.846(3.141～10.882)]were the influential factors for the severity of CI in patients with Parkinson's disease(all P＜0.05).Conclusion The serum levels of NPASDP-4 and MBP in patients with Parkinson's disease were high,and they were closely related to CI and its severity,which may have certain clinical diagnostic value.