Elevated Plasma Homocysteine Level Is Not Primarily Related to Alzheimer's Disease.

Background: A moderate elevation of plasma total homocysteine (tHcy) is considered a potential risk factor for Alzheimer's disease (AD). Methods: We have investigated the main determinants (age, renal impairment, cobalamin/folate status and the presence of vascular disease) of plasma tHcy in 326 patients with AD, and also in 281 patients with mild cognitive impairment (MCI), since about half of these patients develop AD during the first 5 years. Results: Elevated plasma tHcy in patients with AD could mainly be attributed to cobalamin/folate deficiency or renal impairment. Younger patients (below 75 years) with AD and patients with MCI without cobalamin/folate deficiency or renal impairment showed normal levels of plasma tHcy. Conclusion: Our findings suggest that plasma tHcy is not primarily involved in the pathogenesis of AD but rather a reflection of changes of the main determinants of plasma tHcy in AD patients