Abstract: Objective To investigate the effect of serum homocysteine (Hcy) and apolipoprotein E (ApoE) gene polymorphisms on cognitive function in patients with vascular dementia. 
Methods Retrospective analysis was performed on 100 patients with vascular dementia treated in hospitals as research subjects. The cognitive function of the patients was evaluated by the mini-mental state examination (MMSE). Patients with MMSE score of 21-26 were included in the mild group, those with MMSE score of 10-20 were included in the moderate group, and those with MMSE score of 0-9 were included in the severe group. According to the Chinese Guidelines for the Diagnosis and Treatment of Dementia and Cognitive Dysfunction, the patients were given conventional treatment. The main examination items before treatment included plasma Hcy and ApoE gene polymorphisms, and the clinical efficacy was recorded at 3 months after treatment. The relationship of ApoE gene polymorphism and Hcy with cognitive impairment and clinical efficacy in patients with vascular dementia was analyzed. 
Results The MMSE score of 100 patients with vascular dementia was 16.50 (9.00, 20.00), including 24 mild cases, 49 moderate cases and 27 severe cases; the proportion of patients with APOE gene phenotype of ε2/4 and ε4/4 in the severe group was higher than that in the mild and moderate group, and the plasma Hcy level at admission was higher than that in the mild and moderate group, suggesting significant difference (P＜0.05). Multivariate logistic regression analysis showed that plasma Hcy and ApoE genes were risk factors for exacerbation of cognitive impairment in patients with vascular dementia (P＜0.05). In 100 patients with vascular dementia, at 3 months after treatment, 47 cases showed significant improvement, 30 cases were improved, 23 cases were ineffective, and the total effective rate was 77.00%. Binary logistic regression analysis showed that plasma Hcy and ApoE genes could affect the therapeutic effect of patients with vascular dementia (P＜0.05). 
Conclusion ApoE gene polymorphism and Hcy are closely related to the severity and clinical significance of cognitive impairment in patients with vascular dementia. In the future, the severity of cognitive impairment and the risk of ineffective treatment can be evaluated by detecting the ApoE gene polymorphism and Hcy level of patients. Targeted interventions can be taken to improve the clinical efficacy of patients with serious conditions and high risk of ineffective treatment.

Key words: dementia, vascular, cognitive dysfunction, apolipoprotein E