Silent’ Strokes Common and Linked to Dementia

NEW YORK (Reuters Health) – People who experience so-called silent strokes face more than twice the risk of developing dementia as those who have not had strokes that strike without symptoms, according to new study findings released Wednesday.

The results suggest that people who take steps to prevent strokes might also help ward off dementia, including Alzheimer’s disease (news – web sites), said study author Dr. Monique M.B. Breteler, a researcher at Erasmus Medical Center in Rotterdam, the Netherlands.

“Anything that helps to keep your (blood) vessels healthy — blood pressure control, healthy diet, adequate physical exercise, etc. — may help to not only reduce the risk of (heart attack) and stroke but possibly also dementia,” Breteler told Reuters Health.

Silent strokes, as with full-blown strokes, result when blood vessels in the brain become blocked or rupture. However, patients experiencing silent strokes do not have severe headaches, dizziness, difficulty speaking, paralysis or other classic stroke symptoms.

Doctors do not routinely screen patients for silent strokes, which can be detected with an expensive MRI brain scan.

In the March 27th issue of The New England Journal of Medicine (news – web sites), Breteler and colleagues reported on a study of 1,015 people ages 60 to 90 who underwent an initial MRI from 1995 to 1996 and then again from 1999 to 2000. None had dementia at the beginning of the study, but by the end 30 had developed dementia and most cases were diagnosed as Alzheimer’s disease.

There is increasing evidence that blood-vessel damage may contribute to the development of Alzheimer’s disease, the researchers noted, though precisely how is unclear.

Results from the new study showed that people who had evidence of silent strokes on their initial MRI scans had more than double the risk of developing dementia during the study period as those who had not had silent strokes.

Those with silent strokes also experienced greater declines in mental function, but this finding was limited to those who during the study period had additional silent strokes that caused further damage to brain tissue.

Breteler said silent strokes were surprisingly common in the study, present in about one in five participants at the time of the first MRI.

Dr. John P. Blass, a professor of neurology at the Weill Medical College of Cornell University in White Plains, New York, who co-authored an accompanying editorial, agreed with Breteler that the new findings offer “yet another reason to maintain good cardiovascular health.”

But before widespread screening for silent strokes can be recommended, more research is needed to determine if such screening is warranted and to clarify the complex association between strokes and dementia, Blass said in an interview.

SOURCE: The New England Journal of Medicine 2003;348:1215-1222,1277-1278.