New Risk Factor For Dementia

Feb. 14, 2002 -- You can't change most factors, like genes, that determine your risk for Alzheimer's disease or dementia. But new data suggests you may be able to limit your risks by altering your diet or taking dietary supplements.

A study, appearing in the New England Journal of Medicine, finds an association between elevated levels of homocysteine, an amino acid also implicated in heart disease and stroke, and the development of dementia and Alzheimer's disease.

The good news, say experts, is that taking folic acid supplements can lower homocysteine levels, which may make those levels a modifiable risk factor.

Researchers from Boston University and Tufts University in Medford, Mass., used data gathered earlier in what was called the Framingham Study, which aimed to identify factors that contribute to the development of heart disease. In the current study, researchers looked at homocysteine levels taken from blood tests of 1,092 dementia-free subjects aged 65 and older at several stages.

Over the course of eight years, 111 subjects developed dementia, including 83 who developed Alzheimer's disease. When the subject's homocysteine levels were compared, the researchers found that higher levels were associated with increased dementia and Alzheimer's. Specifically, every 5 micromols per liter increase in homocysteine raised the risk of Alzheimer's disease by 40 percent. And a homocysteine level greater than 14 micromols per liter nearly doubled the risk of developing the disease.

Even after adjusting for factors that have been shown in previous studies to affect Alzheimer's disease risk, such as education and genetics, the association still held.

"This suggests that there was an effect of homocysteine on the development of dementia that was independent of the effect of [other] associated risk factors," says Dr. Philip Wolf, professor of neurology at Boston University School of Medicine and principal investigator of the current study and of the Framingham Study.

Lower Homocysteine, Lower Risk?

While the results are promising, no research has yet been conducted to demonstrate that low homocysteine levels are linked to less dementia.

"The key question, which the study doesn't answer, is whether if you lower homocysteine levels, you reduce the risk of Alzheimer's disease," says Dr. Sean Morrison, director of research at the Hertzberg Palliative Care Institute and associate professor in the department of geriatrics and adult development at Mount Sinai School of Medicine in New York City. "I think that [this study] raises the possibility that we may have a future therapy directed at reducing the risk of Alzheimer's disease, but I think that we need to wait for further studies."

In fact, the National Institute of Aging has funded a study to look at the effects of folic acid and vitamins B6 and B12 on homocysteine levels and whether this effect reduces the rate of cognitive decline. That research is currently slated to begin late this year or early 2003.

Yet even if lowering homocysteine is found to have a beneficial effect on dementia, experts say that may not be the whole story.

"Something like 16 percent of all of the Alzheimer's disease [in the current study] could be accounted for by homocysteine," says Wolf. "There's still 84 percent that is attributable to other things. So it's not a single factor, but it's an important factor."

Experts say that people who are concerned about their homocysteine levels can always make sure that they eat a well-balanced diet rich in folic acid, B6 and B12 — and that's good practice at any age.

Spinach, asparagus, turnip greens, lima beans, beef liver, parsley, broccoli and romaine lettuce are all rich in folic acid. Vitamin B12 is naturally found in animal foods including fish, milk and milk products, eggs, meat, and poultry. Fortified breakfast cereals are also an excellent source of vitamin B12, and a particularly good source for vegetarians.Vitamin B6 is found in a wide variety of foods including fortified cereals, beans, meat, poultry, fish, and some fruits and vegetables.