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New Alzheimer's Risk Factor Identified
Feb. 13, 2002 -- High blood levels of a substance called homocysteine have been linked to an increased risk for both heart attack and stroke. Now, new research finds it to be a major risk factor for Alzheimer's disease and other age-related dementias.
If confirmed, the association between homocysteine and three of the major diseases of aging suggests the exciting possibility that these diseases might be prevented by simply taking your vitamins. It is known that B-vitamins like folic acid, B-6, and B-12 lower homocysteine levels. It is not clear, however, whether supplemental doses of these vitamins are protective against disease.
"The good news is that we may have found a potential risk factor for Alzheimer's disease that is modifiable," says Neil Buckholtz, PhD, who is chief of the Dementias of Aging program at the National Institute on Aging (NIA). "We don't know yet whether reducing homocysteine levels will reduce dementia risk, but this is something that can and will be tested in clinical trials."
In the latest homocysteine study, Boston University School of Medicine researchers found a strong link between elevated plasma levels of homocysteine and Alzheimer's risk in a group of 1,092 elderly people enrolled in the ongoing Framingham Heart Study. During eight years of follow up, 111 of the participants developed dementias, including 83 diagnosed with Alzheimer's disease.
Those with elevated blood homocysteine levels at entry into the study were twice as likely to develop Alzheimer's during the follow-up period as those with lower levels of the substance in their blood. The study, published Feb. 14 in The New England Journal of Medicine, is the first to link homocysteine levels in the years before symptoms develop with dementias associated with aging.
"We expected to find some effect, but we did not expect it to be so large," lead author Sudha Seshadri, MD, tells WebMD. "Homocysteine has emerged as a very important risk factor for [heart] disease. Our study suggests that it is also important in Alzheimer's. Now we have to find out if lowering homocysteine levels decreases risk."
The National Institute on Aging is planning a nationwide study to evaluate whether high supplemental doses of folic acid, B-6, and B-12 can slow the rate of mental decline in people with Alzheimer's disease.
And that strategy has already worked to decrease the number of birth defects that are linked to low blood levels of folic acid. In 1998, the Food and Drug Administration mandated that folic acid be added to grain foods like flour, rice, and cereals. Earlier findings from the Framingham Heart Study found that homocysteine levels fell about 7%, and folic acid levels doubled, following the change.
Although hopeful that such an action would successfully decrease the risk of dementia, scientists say that it's still too early to recommend vitamins for this purpose. "Scientifically, it is premature to say that people should take these vitamins in supplement form on the basis of our data and other studies," Seshadri says. "But this reinforces the importance of eating a healthy diet. The best way we know of decreasing homocysteine levels is eating lots of green leafy vegetables, fruits, and whole grains."
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