Finnish study links mouth bacteria to heart disease risk

A Finnish team analyzed atherosclerotic plaque from two groups: 121 people who suffered sudden cardiac death and 96 people who had arteries cleared by endarterectomy. They tested the samples for DNA from Viridians streptococcal, a bacterium commonly found in the mouth and digestive tract. The researchers reported finding the bacteria in more than 40% of plaques in both groups, primarily as a biofilm embedded in the arterial walls. While the bacteria are usually harmless when kept in check, experts say their presence in plaques could signal a link between oral bacteria and cardiovascular risk under certain conditions.

Within the deceased group, 66% of plaque samples contained bacteria, compared with 58% in the endarterectomy group. The most common organism in both groups was oral viridans group streptococci, detected in 42% of the heart‑attack cases and 43% of those who had surgery. In arteries that were not clogged, bacteria were less common. The study also describes demographics: the average age in the fatal group was about 63, nearly three-quarters were men, and the average body mass index was about 30; in the endarterectomy group, the average age was about 69, 72% were men, and BMI averaged about 27. The plaque samples came from individuals who either died of a sudden cardiac event or underwent surgical plaque removal.

The study, published last month in the Journal of the American Heart Association, notes that oral viridans streptococci are among the early colonizers of the dental biofilm. Dr Pekka J Karhunen, study author and professor at Tampere University, said the team "aim to show that there is a biofilm consisting of many bacteria in the atherosclerotic plaques" and that calcification of the biofilm on teeth might be involved in the calcification of coronary arteries. He added that bacteria can remain dormant inside the biofilm, but activation by infection or other triggers may allow them to spread to the plaque and provoke inflammation and clotting.

The findings also raise questions about the mechanisms by which mouth bacteria could influence cardiovascular events. Doctors caution that the presence of bacteria in plaques does not prove causation, but the data point to a potential pathway in which oral bacteria contribute to inflammation and thrombosis. Endocarditis, an infection of the heart's inner lining and valves, affects between about 10,000 and 30,000 Americans each year and can send bacteria into the bloodstream to lodge in arteries.

Experts say the results reinforce the importance of oral hygiene. Dr Elizabeth Klodas, chief medical officer and founder of Step One Foods, told Prevention magazine that the study underscores how interconnected body systems are and that regular dental checkups, brushing and flossing can support heart health. Researchers also noted that the project is exploring the possibility of vaccines that target the biofilm and bacterial-induced thrombosis.

Context and outlook: cardiovascular disease remains the leading global killer. In the United States, cardiovascular disease accounts for about one in three deaths, with millions affected. Public health authorities project that by 2050 more than 60% of Americans could have some form of heart disease. The new study adds to a broader effort to understand how chronic conditions, lifestyle and infection risk factors intersect in the progression of atherosclerosis.

While the results are intriguing, researchers caution that they are not definitive. More work is needed to determine whether reducing oral bacterial load translates to lower atherosclerotic risk or whether vaccines against bacterial biofilms could cut the incidence of thrombosis. In the meantime, medical experts say maintaining good oral hygiene is a prudent step for overall health.