A preliminary study involving more than 6,000 people suggests that flossing at least once a week may be linked to a lower risk of stroke caused by a blood clot blocking brain blood flow and irregular heartbeats.
The findings, published by the American Stroke Association, are described as one of the first large-scale investigations of its kind in the United States. The study will be presented at the American Stroke Association’s International Stroke Conference 2025, which takes place in Los Angeles from Feb. 5-7.
The study found that flossing was associated with a 22 per cent lower risk of ischemic stroke, a 44 per cent lower risk of cardioembolic stroke (caused by blood clots traveling from the heart), and a 12 per cent lower risk of atrial fibrillation (AFib), a common type of irregular heartbeat.
Oral health behaviours are linked to inflammation and artery hardening. Flossing may reduce stroke risk by lowering oral infections and inflammation and encouraging other healthy habits
Study lead author Dr. Souvik Sen
Studying oral hygiene behaviours
Among participants who reported flossing, 4,092 had not experienced a stroke, and 4,050 had not been diagnosed with AFib. Most significantly, researchers found that the associated lower risk was independent of regular brushing, routine dental visits, or other oral hygiene behaviours.
“We aimed to determine which oral hygiene behaviour—dental flossing, brushing, or regular dentist visits—has the greatest impact on stroke prevention,” said study lead author Dr. Souvik Sen, chair of the Department of Neurology at Prisma Health Richland Hospital and the University of South Carolina School of Medicine in Columbia, S.C.
“Oral health behaviours are linked to inflammation and artery hardening. Flossing may reduce stroke risk by lowering oral infections and inflammation and encouraging other healthy habits,” Sen added.
According to the Canadian Community Health Survey (CCHS), 78.3% of Canadians aged 12 and older reported brushing their teeth at least twice a day, but fewer than half (43%) said they floss daily.
In the U.S., data from the National Health and Nutrition Examination Survey (NHANES) 2011–2014 found that about 32% of adults aged 30 and older floss daily, with women (37%) flossing more frequently than men (26%).
3.5B people have oral diseases
Sen cited a World Health Organization (WHO) report that found oral diseases affected 3.5 billion people worldwide in 2022, with three out of four people impacted living in middle-income countries.
According to Sen, the prevalence of oral disease makes it “one of the most widespread health conditions.”
“Many people have expressed that dental care is costly. Flossing is a healthy habit that is easy to adopt, affordable and accessible everywhere,” Sen added.
Study limitations include the reliance on self-reported data from a questionnaire. Additionally, while the study followed participants for 25 years, it primarily tracked stroke and heart outcomes, with no follow-up on flossing or other oral hygiene behaviours over time, Sen said.
