In an initial, randomized controlled study on elderly subjects with increased dementia risk (mild cognitive impairment according to 2004 Petersen criteria), the authors of this study found that high-dose B-vitamin treatment (folic acid 0.8 mg, vitamin B6 20 mg, vitamin B12 0.5 mg) slowed shrinkage of the whole brain volume over a 2 year period. In this report, they demonstrate that B-vitamin treatment reduces, by as much as seven fold, the cerebral atrophy in those gray matter brain regions specifically vulnerable to the Alzheimer Disease process, including the medial temporal lobe. In the placebo group, higher homocysteine levels at baseline are associated with faster gray matter atrophy, but this deleterious effect is largely prevented by B-vitamin treatment. The beneficial effect of B vitamins was confined to participants with high homocysteine (above the median, 11 µmol/L). In these subjects, a causal Bayesian network analysis indicates the following sequence of events: B vitamins lower homocysteine, which directly leads to a decrease in gray matter atrophy, thereby slowing cognitive decline. They conclude that B-vitamin supplementation can slow the atrophy of specific brain regions that are a key component of the Alzheimer Disease process and that are associated with cognitive decline. They suggest that further B-vitamin supplementation trials focusing on elderly subjects with high homocysteine levels are warranted to see if progression to dementia can be prevented.
Douaud G, Refsum H, de Jager CA, Jacoby R, E Nichols T, Smith SM, Smith AD: Preventing Alzheimer‘s disease-related gray matter atrophy by B-vitamin treatment. Proc. Natl. Acad. Sci. USA [Epub ahead of print, May 20, 2013].