Associations between Alzheimer's disease and blood homocysteine, vitamin B12, and folate: a case-control study.

BACKGROUND There is a growing focus on nutritional therapy for Alzheimer's disease (AD), and controversy exists regarding the association between AD and homocysteine (Hcy), vitamin B12, and folate levels. OBJECTIVE The present study evaluated the association between AD and the combined levels of Hcy, vitamin B12, and folate. METHODS This case-control study consisted of 115 patients with AD and 115 matched controls. Serum folate and vitamin B12 were measured using an automated immunoassay analyzer. Plasma Hcy was measured using high-performance liquid chromatography. The association between AD and Hcy, vitamin B12, and folate was analyzed using binary logistic regression, adjusted for age and sex. RESULTS With the combination of normal blood Hcy, vitamin B12, and folate levels as the reference category, low vitamin B12 in subjects with normal Hcy and folate was associated with AD (adjusted odds ratio [OR], 4.6; 95% confidence interval [CI]: 1.6-13.2). The combination of low vitamin B12 and folate in subjects with normal Hcy was associated with AD (adjusted OR, 4.3; 95% CI: 1.3-14.6). The combination of high Hcy and low folate levels in patients with normal vitamin B12 was associated with AD (adjusted OR, 17.0; 95% CI: 5.4- 53.4). The combination of high Hcy, low vitamin B12, and any folate level was associated with AD (adjusted OR, 30.5; 95% CI: 9.7-95.9). CONCLUSION Vitamin B12 was directly associated with AD. The combination of high Hcy, low vitamin B12, and any folate level represented the poorest association with AD.