"Since B vitamins and foods fortified with folate can reduce homocysteine levels, this study suggests that B vitamin supplementation may be appropriate for most adults. It warrants a large placebo-controlled study of folate, and vitamins B6 and B12 in people at risk from dementia and stroke," says lead author Stephen P. McIlroy, Ph.D., a lecturer in geriatric medicine at Queen's University in Belfast, Ireland.

McIlroy and his colleagues studied 83 Alzheimer's patients (average age 77); 78 patients with dementia caused by poor blood flow to the brain, a condition called vascular dementia (average age 77); 64 stroke patients (average age 74) and 71 healthy volunteers (average age 74).

There is some disagreement among scientists about what constitutes an elevated homocysteine level. In this study, researchers picked the upper quartile of homocysteine levels of the healthy volunteers, which was 13.3 micromoles per liter (mmol/L) or higher - as an elevated level.

They also collected data on education, diet, blood pressure, cholesterol, and smoking history. Several of these factors are associated with the risk for Alzheimer's disease, and smoking directly affects homocysteine levels, he says. The researchers also used DNA testing to determine if any of the subjects had a variation in the gene methylenetetrahydrofolate (MTHFR), which can adversely affect folate metabolism.

After correcting for other risk factors, elevated homocysteine was associated with a 2.9 times greater risk for Alzheimer's disease than risk in volunteers with lower levels of homocysteine. The stroke risk was 5.5 times greater, and for vascular dementia, it was 4.9 times greater. These findings were not related to having the MTHFR mutated gene. (4)

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