Flossing your teeth 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, according to a preliminary study to be presented at the American Stroke Association's International Stroke Conference 2025. The meeting is in Los Angeles, Feb. 5-7, 2025, and is a world premier meeting for researchers and clinicians dedicated to the science of stroke and brain health.

"A recent global health report revealed that oral diseases -- such as untreated tooth decay and gum disease -- affected 3.5 billion people in 2022, making them the most widespread health conditions," said study lead author Souvik Sen, M.D., M. S., M.P.H, chair of the Department of Neurology, Prisma Health Richland Hospital and the University of South Carolina School of Medicine in Columbia, South Carolina. "We aimed to determine which oral hygiene behaviour -- dental flossing, brushing or regular dentist visits -- has the greatest impact on stroke prevention."

The Atherosclerosis Risk in Communities (ARIC) study, one of the first large-scale investigations of this kind in the U.S., assessed the home use of dental floss through a structured questionnaire of more than 6,000 people. Among those who reported flossing, 4,092 had not experienced a stroke, and 4,050 had not been diagnosed with an irregular heartbeat known as atrial fibrillation (AFib).

Participants were asked about their status regarding high blood pressure, diabetes, high cholesterol, smoking, body mass index, education, regular brushing and dentist visits. During the 25 years of follow-up, 434 participants were identified as having strokes, of which 147 were larger artery brain clots, 97 were heart-driven clots and 95 were hardening of the smaller arteries. Additionally, 1,291 participants were noted to have experienced AFib.

The analysis found:

Researchers were surprised by the reduction of irregular heartbeats, or AFib. AFib is the most common form of irregular heartbeat. It can lead to stroke, heart failure or other cardiovascular complications. More than 12 million people are projected to have AFib in the United States by 2030, according to the American Heart Association's 2025 Heart Disease and Stroke Statistics.

"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 said. "Many people have expressed that dental care is costly. Flossing is a healthy habit that is easy to adopt, affordable and accessible everywhere."

Study limitations include that data were based on answers to a questionnaire, and the 25-year follow-up appears to have focused on stroke and heart outcomes only. There was no follow-up concerning flossing or other oral behaviours over the years, Sen said.

"This study offers more insights into the specific dental health behaviours that may be linked to stroke risks and potential risk reduction. With further research, dental health practices could possibly be incorporated into the "Life's Essential 8" risk factors, which include diet, physical activity, nicotine exposure, sleep, body mass index, blood pressure, blood glucose and blood lipids," said Daniel T. Lackland, Dr.P.H., FAHA, American Heart Association EPI and Stroke Council member and professor of epidemiology and director of the Division of Translational Neurosciences and Population Studies in the department of neurology at the Medical University of South Carolina in Charleston. Lackland was not involved in this study.