THURSDAY, Oct. 3, 2002 (HealthDayNews) -- Moderately high blood levels of the amino acid homocysteine -- levels seen in a quarter of the adult population -- are linked to a substantial increase in the risk of Alzheimer's disease, other dementias and stroke.
"People deemed to have normal levels of homocysteine are in fact at elevated risk for stroke and dementia," says Stephen P. McIlroy, a lecturer in geriatric medicine at Queens University in Belfast, Northern Ireland. He reports the finding in the October issue of Stroke.
The research shows the need for a large-scale study to see whether taking supplements containing folic acid and B vitamins, which reduce blood levels of homocysteine, can lower the incidence of Alzheimer's disease and stroke, McIlroy says.
Other studies have linked elevated homocysteine levels to Alzheimer's disease, heart disease and stroke, but McIlroy's study finds a risk at lower levels than have been reported. He and his colleagues looked at homocysteine levels in 83 Alzheimer's patients, 78 patients with dementia caused by poor blood flow to the brain, 64 stroke patients and 71 healthy volunteers. All were in their 70s.
The study used a cutoff line of homocysteine levels found in the upper 25 percent of the healthy volunteers. After correcting for known risk factors such as smoking, blood cholesterol and blood pressure, the researchers say that readings above that level are associated with a 2.9 times greater risk of Alzheimer's disease, a 5.5 times greater risk of stroke, and a 4.9 times greater risk of dementia due to poor blood flow to the brain.
Laboratory studies have shown that homocysteine and molecules produced when it is metabolized can attack blood vessels and nerves. However, there has been a running debate about whether elevated homocysteine levels cause blood vessel and nerve damage or are just associated with processes that cause the damage. The case for cause-and-effect is compelling, McIlroy says.
"There are too many studies saying that high homocysteine levels are linked to dementia and stroke," he says. "I certainly think it is a cause, a very easily modifiable risk factor for dementia and stroke."
However, Bill Thies, vice president for medical and scientific affairs for the Alzheimer's Association, says it's too early to be recommending supplements for prevention.
"These kinds of studies don't give you cause-and-effect information," he says. "They just point you in a direction."
As for a prevention trial, Thies says it would be more difficult to do in the United States than in Northern Ireland. Many foods here are fortified with folic acid to prevent birth defects, something that's not done there, he says, and that might muddy the results of any American trial.
A study of Alzheimer's patients to see whether folic acid and vitamins B12 and B6 can slow progression of the disease is being started in the United States, Thies says. Positive results from that trial could lead to a bigger preventive study, he says.
The Alzheimer's Association has no official position on self-medication with folic acid and vitamin B, Thies says. A basic rule is that "anyone should not be taking anything without consulting their physician, and if you take anything, you should tell your physician," he says.
Folic acid and vitamin B supplements are generally agreed to be innocuous, Thies says, but "there is no such thing as a completely safe drug." Since various studies have suggested that taking aspirin, other anti-clotting drugs, estrogen or other medications might reduce the risk of Alzheimer's, "you could end up taking a fair collection of pills without evidence that they might be effective or what the risk is," he says.
What To Do
You can get more information about homocysteine and the blood vessels from the American Heart Association and about Alzheimer's disease from the Alzheimer's Association.
