The ongoing "Maine-Syracuse Study," which began in l974 and involves more than 2,700 people also looked at homocysteine levels in those with a gene variation linked to Alzheimer's Disease known as apolipoprotein E4, or ApoE-e4.

"The importance of our recent paper in Neuroscience Letters is that we find that the combination of elevated homocysteine and the presence of the ApoE-e4 allele represent a higher degree of risk for lower cognitive performance than the presence of either risk factor alone," one of the study's authors, Merrill Elias of the University of Maine in Orono, said in a statement.

"There currently is no practical way that one can modify the ApoE-e4 alleles so that they do a better job of repairing brain cells, but there is hope for prevention and reversal of cognitive deficit related to elevated homocysteine by reducing homocysteine levels."

The study authors suggest physicians and nutritionists use vitamins -- especially increasing the levels of folate, vitamin B6 and vitamin B12 -- to help reduce homocysteine levels in their patients.