By
American Heart Association News May 23, 2019
Bacteria commonly seen in the mouth
has been found in the brains of people who have had a stroke, a new study
shows.
The Finnish research group behind
the new findings has been studying a possible association between bacterial
infections and cardiovascular disease for more than 10 years. Their study,
published Thursday in the Journal
of the American Heart Association, looked for signs of bacteria
in blood clots removed from 75 patients who were treated for an ischemic stroke
at Tampere University Hospital in Finland between 2013 and 2017.
Ischemic stroke is caused by a
blockage in a blood vessel in the brain. It accounts for about 87% of all
strokes.
The study found that 84% of the
participants, or 63 of them, had bacterial DNA in their blood clot. Among them,
59 had a strain of streptococci commonly found in the mouth that can cause
infections if they get into the bloodstream.
The work is "the first to show
common presence of (this) bacterial DNA in ischemic stroke patients," said
Olli Patrakka, the study's lead author.
The bacteria involved, called
viridans streptococci, are believed to cause endocarditis, an infection of the
lining, valves or muscles of the heart.
Patrakka, a graduate student in the
Department of Forensic Medicine at Tampere University, said his colleagues in
2013 found the same strain of streptococci in blood clots removed from patients
who had a heart attack. Additional studies found the same bacteria in patients
who had a ruptured brain aneurysm or a blood clot in their leg.
"Our results suggest that
bacteria might have a role in the (development) of serious complications
related to atherosclerosis" – the buildup of plaque in the arteries,
Patrakka said.
Studies have identified high blood
pressure, high cholesterol, physical inactivity, diabetes, smoking and obesity
as risk factors for heart disease. In 2012, a committee of the American Heart
Association convened an expert panel to review the evidence on oral health and
cardiovascular disease and concluded there was not enough evidence to show gum
disease caused by bacteria was a direct cause of heart disease or that treating
the gum disease would prevent heart disease.
Dr. Peter B. Lockhart, research
professor in the Department of Oral Medicine at Carolinas Medical Center in Charlotte,
North Carolina, was lead author of the AHA scientific statement. Although the
new study clearly found oral bacteria in the brain, he said the significance of
the finding is open to question.
Bacteria is present in the mouth,
and it's not uncommon for it to enter the bloodstream, Lockhart said, whether
or not a person is healthy or has periodontal disease.
"We now know that bacteria
exist throughout the body, including in the blood," which was previously
thought to be sterile. "Finding evidence of bacteria in blood clots
doesn't mean they have a role in the disease process," he said.
But Patrakka said his research
suggests regular dental checkups might help reduce the risk of heart disease.
Bacterial plaque buildup on the
teeth can cause periodontal disease, an inflammation of the tissues around the
teeth. About 47% of adults ages 30 and older have some form of periodontal
disease, according to the Centers for Disease Control and Prevention.
"We believe that future studies
will strengthen the view that regular dental care has a more important role
than previously thought in the health of people," Patrakka said.
But for now, Lockhart expects
doctors will stick to the clear-cut risks.
"If you are a
cardiologist," he said, "you are going to focus your time with
patients talking about smoking, diet, exercise and other well-documented
contributors to cardiovascular disease."
If you have questions or comments about this story, please
email editor@heart.org.
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