Plasma homocysteine and risk of mild cognitive impairment.

BACKGROUND AND OBJECTIVE There are conflicting data relating homocysteine levels to the risk of Alzheimer's disease (AD). We sought to explore whether fasting plasma homocysteine is associated with the risk of mild cognitive impairment (MCI), an intermediate stage to dementia. METHODS Fasting levels of plasma homocysteine were obtained from 678 elderly subjects chosen at random from a cohort of Medicare recipients. There were longitudinal data in 516 subjects without MCI or dementia at baseline who were followed for 2,705 person-years. The relation of plasma homocysteine with prevalent and incident all-cause MCI, amnestic MCI and non-amnestic MCI was assessed using logistic and Cox proportional hazards regression analyses. RESULTS There were 162 cases of prevalent MCI and 132 cases of incident MCI in 5.2 years of follow-up. There was no association between plasma homocysteine and prevalence of MCI or amnestic or non-amnestic MCI in the cross-sectional analyses. There was no association between higher homocysteine levels and a lower risk of all-cause MCI. Consistent with the cross-sectional analyses, there was no specific association with the amnestic or non-amnestic subtype of MCI in crude or adjusted models. CONCLUSION Plasma homocysteine levels measured at baseline were not related to MCI or its subtypes in an elderly multiethnic cohort.