July 8, 2002 -- Particularly potent strains of bacteria known to cause ulcers may also share the blame for prompting some of the most common types of stroke, according to a new study. Researchers say the findings show the evidence implicating infection and inflammation as key suspects in the development of heart disease and stroke is mounting.
Although previous studies have linked the bacterium H. pylori to heart disease and strokes caused by narrowing of the arteries, some of the findings have been conflicting. But now, researchers say only certain strains of especially damaging bacteria may increase stroke risk.
For the first time, researchers from Tor Vergata University in Rome have found that these strains are much more common in the blood of people who have suffered a stroke caused by clogged blood vessels. This type of stroke accounts for about 80% of all strokes and occurs when a blood vessel that supplies blood to the brain becomes clogged or obstructed.
H. pylori causes ulcers in the stomach, but the study authors say the bacteria make an already bad situation worse when it comes to clogging the large arteries that lead to the brain. Certain strains of the bacteria produce a substance that attacks vulnerable areas of the artery wall and causes inflammation and swelling -- further reducing blood flow to the brain and increasing the risk of stroke.
The study compared people who had suffered an ischemic stroke to a similar group of healthy people.
Researchers found levels of overall H. pylori infection were about the same among all the study participants. But those who had suffered a stroke from a blocked large artery had significantly higher levels of the more potent strains of the bacteria.
The study also found that levels of a substance known as C-reactive protein (CRP) that indicates inflammation within the body were also higher in the stroke groups. But patients with the potent strains of H. pylori had the highest CRP levels, which suggests that they had more severe inflammation in response to infection.
Researchers say that if more studies confirm this finding, treating patients with H. pylori infection may be an easy way to reduce the risk of stroke.
Their study is published in the July 8 issue of Circulation: Journal of the American Heart Association.