Relationships between plasma homocysteine levels and cognitive impairment: a cross-sectional study based on the rural populaiion aged 40 years old and above in Xi'an, China

Objective To investigate the relationship between plasma homocysteine (Hcy) levels and cognitive impairment (CI).Methods From November 2018 to January 2019, baseline data and cognitive function were collected from the participants aged ≥40 years who lived in two villages in Huyi District, Xi'an, China. Their global cognitive function was assessed by Mini-Mental State Examination (MMSE) and the diagnosis of cognitive impairment was based on international guidelines.Fasting blood was collected in the morning, and plasma Hcy level was measured by the chemiluminometric assay. Multivariate Logistic regression analysis, subgroup analysis, and interaction analysis were performed to investigate the relationship between plasma Hcy and CI. Results A total of 1805 subjects were included in the analysis. There were 1056 females (58.5%), age ranged from 40 to 88 years [mean (58.99±9.52) years], and 145 participants (8.0%) were diagnosed as CI. The median plasma Hcy levelin the overall population was 14.1 (11.6, 17.8) μmol/L. There were 729 (40.4%) subjects in the HHcy group (＞15.0 μmol/L) and 1076 (59.6%) in the normal group (≤15.0 μmol/L).Univariate analysis showed that the prevalence of CI was higher in the HHcy group than in the normal Hcy group (11.4%vs.5.8%, P＜0.001). In multivariable Logistic regression fully adjusted for potential confounders, each 1 μmol/L increase in plasma Hcy level was associated with a 3.0% increased risk of CI (OR=1.030, 95%CI ：1.012-1.048, P=0.001). Interaction analysis indicated that sex, age, BMI, systolic blood pressure, history of stroke, and diabetes did not significantly modify this association. Conclusion Elevated plasma Hcy levels are associated with an increased risk of CI in people aged ≥ 40years.This indicates that HHcy may be a risk factor for CI.