Thesis author Dr. Dimitri Zylberstein, of Sahlgrenska Academy at the University of Gothenburg in Sweden, said the discovery could lead to a new and simple way of determining who is at risk for Alzheimer's long before there are any signs of the illness.
Zylberstein used data from the Prospective Population Study of Women in Gothenburg, which was started at the end of the 1960s when almost 1,500 women age 38-60 were examined, asked questions about their health and had blood samples taken.
Nearly all of the samples have now been analyzed and compared with information on who went on to suffer from Alzheimer's and dementia much later.
"Alzheimer's disease was more than twice as common among the women with the highest levels of homocysteine than among those with the lowest, and the risk for any kind of dementia was 70 percent higher," Zylberstein said in a statement.
The researchers do not yet know whether it is the homocysteine itself that damages the brain, or whether there is some other underlying factor that both increases levels of the homocysteine and causes dementia.
Elevated homocysteine levels have been linked to certain vitamin deficiencies -- B12 and folate.
