Researchers say that high levels of the amino acid homocysteine may increase the risk of brain atrophy and blood vessel disease, researchers report. It is still too soon to be certain that lowering homocysteine levels will reduce the risk of Alzheimer's and other types of dementia, but the approach is worth investigating.
Prior research has shown that elevated levels of homocysteine may increase the risk of heart disease and stroke. Diet has a major effect on homocysteine levels. Folic acid and other B vitamins may lower homocysteine levels by breaking down the amino acid. The benefits of lowering homocysteine levels have not been proven, however.
Instead, Miller's team found that people with vascular disease, including those who had had a heart attack or stroke or who had evidence of vessel disease on a brain scan, had higher levels of homocysteine in the blood, regardless of whether they had Alzheimer's.
"This is consistent with many studies that have found high blood levels of homocysteine to be a risk factor for vascular disease," Miller said. The researchers also found that people with Alzheimer's were more likely to have low levels of vitamin B6. This vitamin may be important for memory, Miller explained. According to the report, the study raises the possibility that vitamin B6 supplements would help Alzheimer's patients, but Miller noted that the effects of the vitamin have not yet been established.
A second study published in the same journal included 36 healthy elderly people who underwent homocysteine testing and brain scans to detect brain atrophy. Participants with more extensive brain atrophy were more likely to have higher blood levels of homocysteine, according to a team led by Dr. Perminder Sachdev of the University of New South Wales in Australia.
The presence of vascular disease did not explain the connection, Sachdev told Reuters Health. Still, the Australian scientist said that more research is needed to prove that high homocysteine levels lead to brain atrophy. He pointed out that homocysteine levels did not predict how well participants performed on tests of mental ability.
"If there was indeed increased brain atrophy, it was not severe enough in this otherwise healthy group to significantly impact on functioning," he said. Although Sachdev noted that more research is needed, he said that the current scientific evidence is "persuasive enough for a public awareness campaign about homocysteine levels, especially in those at risk for coronary artery disease, stroke and dementia."
He noted that folic acid supplements can return homocysteine levels to normal. The studies "provide important leads but no proof" that high homocysteine levels lead to mental decline, according to an accompanying editorial by Dr. James F. Toole of Wake Forest University in Winston-Salem, North Carolina, and Dr. Clifford R. Jack of the Mayo Clinic in Rochester, Minnesota.
Still, the research is "exciting," Toole said in a news release, since it is possible to lower homocysteine levels with vitamins B6, B12 and folic acid. Toole is currently investigating whether these supplements can reduce the risk of stroke. Another important area of research, according to Toole, is to see whether lowering homocysteine with vitamins will prevent Alzheimer's and other forms of dementia.