A discovery by researchers could lead to a new and simple way of determining which women are at risk of Alzheimer's disease by means of a blood test long before there are any signs of the illness. A study by the researchers has revealed that middle-aged women with high levels of the amino acid homocysteine in their blood are twice as likely to suffer from Alzheimer's disease many years later.

Almost 1,500 women between the ages of 38 and 60 were examined at the end of the 1960s, 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 disease 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 per cent higher," says Dimitri Zylberstein, study author.

Homocysteine is an amino acid that is important for the body's metabolism. It is known that high levels of homocysteine can damage the blood vessels and increase the risk of blood clots. Previous longitudinal studies linking homocysteine and dementia had 8 years of follow-up at most. The present study is by far the longest one with follow-up time of 35 years. The study is also the first to show association between homocysteine levels in middle aged women and dementia development several decades later. 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.

Historically elevated homocysteine levels were related to certain vitamin deficiencies (B12 and folate). Today we know that high homocysteine levels might be present even with perfectly normal vitamin status. "These days we in our clinical practice use homocysteine analyses mainly for assessment of vitamin status. However, our results mean that we could use the very same analysis for assessment of individual's risk profile for dementia development. This opens the possibility for future preventive treatment at a very early stage", says Zylberstein.

The study also looks at a gene which, in some variants, appears to offer protection against dementia. "We have only been able to carry out a genetic analysis on just over 550 of the blood samples from the Prospective Population Study of Women, and want to undertake bigger studies before we can say for sure that the gene really does protect against dementia," says professor Lauren Lissner, study supervisor. "We hope to be able to perform the same analysis on more samples from the study."
References:
1. Dimitri Zylberstein, et al. Homocysteine and vascular morbidity and dementia in women. A prospective population study. Sahlgrenska Academy, University of Gothenburg.