Oral bacteria linked to higher stroke risk

Oral bacteria may be involved in several kinds of stroke, including brain hemorrhages and strokes that lead to dementia, says a new study. Strokes are characterised as either ischemic strokes, which involve a blockage of one or more blood vessels supplying the brain, or hemorrhagic strokes, in which blood vessels in the brain rupture, causing bleeding.

"This study shows that oral health is important for brain health. People need to take care of their teeth because it is good for their brain and their heart as well as their teeth," said study co-author Robert Friedland from University of Louisville School of Medicine in the US.

Friedland collaborated with researchers at the National Cerebral and Cardiovascular Center in Osaka, Japan who observed stroke patients to gain a better understanding of the relationship between hemorrhagic stroke and oral bacteria.

Among the patients who experienced intracerebral hemorrhage (ICH), 26 per cent were found to have a specific bacterium in their saliva, cnm-positive S. mutans. Among patients with other types of stroke, only six per cent tested positive for the bacterium.

The researchers also evaluated MRIs of study participants for the presence of cerebral microbleeds (CMB), small brain hemorrhages which may cause dementia and also often underlie ICH.

They found that the number of CMBs was significantly higher in participants with cnm-positive S. mutans bacteria than in those without. The authors believe that the S. mutans bacteria may bind to blood vessels weakened by age and high blood pressure, causing arterial ruptures in the brain, leading to small or large hemorrhages. (The study was published online in the journal Scientific Reports.)