Plasma homocysteine and cognitive impairment in an older British African-Caribbean population

OBJECTIVES: To investigate the association between homocysteine concentrations and cognitive impairment in an older African-Caribbean population. To investigate other measures of risk for vascular disease and nutritional status as potential confounding factors. DESIGN: A secondary analysis from a cross-sectional community study. SETTING: The sample was drawn from registration lists for seven primary care services in south London, United Kingdom. PARTICIPANTS: Two hundred forty-eight individuals aged 55 to 75 who were born in a Caribbean nation and for whom homocysteine concentrations had been ascertained. MEASUREMENTS: Plasma homocysteine and serum folate were assayed from frozen samples. Cognitive impairment as a composite measure was derived from 11 psychometric tests. Other measures of risk for vascular disease were considered as potential confounding factors: diagnosed hypertension/diabetes mellitus; physical exercise; and concentrations of cholesterol, triglycerides, and fibrinogen. RESULTS: Cognitive impairment was classified in 68 (27%) participants. Raised homocysteine (highest quartile: >13.85 mumol/L) was significantly associated with cognitive impairment (odds ratio (OR) = 2.50, 95% confidence interval (CI) = 1.33-4.69). This association persisted after adjustment for age, occupation, other measures of vascular risk, folate, body mass index, and waist:hip ratio (OR = 3.00, 95% Cl = 1.35-6.69). As with other risk factors for vascular disease in this sample, the association was significant only in those with less education (P-value for interaction =.049). CONCLUSION: Raised homocysteine was associated with cognitive impairment in this sample, but this was modified by previous educational attainment. This association was independent of other measures of vascular risk and was not explained by folate concentrations.