Homocysteine, vascular dementia and Alzheimer's disease.

There is some evidence from recent observational studies that hyperhomocysteinemia is a risk factor for cognitive dysfunction, including Alzheimer's disease and vascular dementia. There are only a few intervention studies, and the results are disappointing for such a frequent disease. Prospective double-blind and placebo-controlled intervention studies are not available. If homocysteine-lowering therapy will be in the running for the prevention and treatment of dementia, we must be able to diagnose the disease at a preclinical stage (i.e. 5 or 10 or 20 years before the disease becomes clinically overt for Alzheimer's disease). At the moment, there are insufficient data to support a vitamin B12, B6 or folate therapy in the prevention or treatment of patients with dementia.