FRIDAY, April 28, 2006 (HealthDay News) -- Tiny blood clots that originate in the heart and wander to the brain could cause Alzheimer's disease and other forms of dementia, a British study indicates.
The researchers found these clots, formally called cerebral emboli, in the brains of 40 percent of 85 people with Alzheimer's disease and 37 percent of people with vascular dementia, according to their report in the April 28 issue of the British Medical Journal. Physicians from the University of Manchester found the same clots in only 14 percent to 15 percent of normal adults tested in the study.
The cerebral emboli "may represent a potentially reversible or treatable cause of dementia," the researchers wrote.
Cerebral emboli are a known cause of stroke. They often form in the circulatory systems of people with atrial fibrillation, an abnormal heart rhythm that enhances clot formation by causing blood to pool. They have not previously been associated with dementia.
"This is another indication that Alzheimer's disease probably is not just one disease," said Dr. Julie A. Schneider, an associate professor of neurology and neuropathology at the Rush Alzheimer's Disease Center in Chicago. "There are probably multiple things happening in the brains of older people, and some of them are vascular."
The finding fits in with the work done at the Chicago center on brain function and blood flow in older people, Schneider said. Cerebral emboli could interact with other dementia risk factors, lowering the threshold at which Alzheimer's disease or a related condition occurs, she said.
The British report "certainly needs follow-up," in part because it leaves some questions unanswered, Schneider said.
The answer to those questions might be available soon, said study author Dr. Charles McCollum, a professor of surgery at the University of Manchester.
"Were in the process of completing a two-year follow-up," McCollum said. "We dont know the results yet, but we should be publishing them shortly. After that, we can think about inhibiting the emboli with medication."
The major question that Dr. George Bartzokis, a professor of neurology at the University of California, Los Angeles, would like to have answered is the effect over time of the presence of cerebral emboli in older people.
The study measured cerebral emboli at one point in time, Bartzokis said. "For the patients, the issue would be are those with cerebral emboli doing worse over time than those without them?" he said. "For the normals, the question is whether those with cerebral emboli will get Alzheimer's disease."
Bartzokis had other questions about the study. He said the high incidence of cerebral emboli found not only in people with dementia but also in normal participants was "surprising." And the study excluded people taking anti-clotting medications such as aspirin, Bartzokis noted. Perhaps having older people take aspirin might reduce the risk of dementia, he said.
The results "clearly are something that should be looked into further," Bartzokis said. "But implying that emboli might be universal in dementia -- that is taking a huge leap."
More information
The role of cerebral embolism in stroke is described by the American Heart Association.
