A preliminary study presented at the American Stroke Association's International Stroke Conference 2025 suggests that a common mouth and gut bacteria, Streptococcus anginosus, may be associated with increased stroke risk and poorer patient outcomes. Researchers from the National Cerebral and Cardiovascular Center in Osaka, Japan, conducted a study examining bacteria in stroke patients' saliva and gut samples. They discovered that Streptococcus anginosus was significantly more abundant in stroke patients compared to a control group of similar-aged individuals without stroke history.
The study found that Streptococcus anginosus in the gut was independently associated with 20% higher odds of stroke after controlling for vascular risk factors. Conversely, other bacteria like Anaerostipes hadrus and Bacteroides plebeius were associated with decreased stroke risk. During a two-year follow-up, stroke survivors with Streptococcus anginosus in their gut demonstrated a significantly higher risk of death and major cardiovascular events compared to those without the bacteria.
Lead researcher Shuichi Tonomura suggested that future medical interventions might include quick tests to detect harmful bacteria in the mouth and gut, potentially helping calculate stroke risk. The findings also emphasize the importance of maintaining good oral hygiene and preventing tooth decay. The researchers acknowledged limitations in their study, noting that the research was conducted in a Japanese population with a relatively small sample size of 189 stroke patients and 55 non-stroke participants. This means the findings may not be fully generalizable to other populations or more diverse groups.
Dr. Louise D. McCullough, who was not involved in the study, highlighted the potential for future research examining bacteria in people with stroke risk factors to enhance understanding of bacterial relationships to stroke risk. The study underscores the complex interactions between oral and gut microbiota and their potential implications for cardiovascular health, suggesting that bacterial composition could be a significant factor in stroke risk and outcomes. The research was presented at the American Stroke Association's International Stroke Conference 2025, which can be found at https://professional.heart.org/en/meetings/international-stroke-conference.
