Skip the Floss? You Might Raise Your Risk of Stroke

Once-a-Week Flossing Might Cut Stroke Risk by Up to 44%, New Study Shows
An important new study suggests that a simple habit many patients overlook—flossing—may offer protection against certain types of stroke and irregular heart rhythms. The research finds that flossing at least once a week is associated with a significantly reduced risk of ischemic stroke, cardioembolic stroke (blood clots traveling from the heart), and atrial fibrillation (AFib), a common arrhythmia strongly linked to stroke. These results were presented at a major international stroke conference and may shift how clinicians view oral hygiene in cardiovascular and brain health prevention.

Key Findings: How Much Risk Is Lowered
Researchers followed over 6,200 adults for 25 years, assessing their flossing habits, other oral health behaviors, and cardiovascular outcomes. Participants were grouped based on whether they flossed at least once a week, with further adjustments for other health and lifestyle factors, including toothbrushing, dental visits, blood pressure, cholesterol, smoking, BMI, and more.

The core results:

• 22% lower risk of ischemic stroke for those who flossed weekly compared to those who did not.
  
  
• 44% lower risk of cardioembolic stroke — strokes caused by clots that form in the heart and travel to the brain.
  
  
• Approximately 12% lower risk of developing atrial fibrillation (AFib).
  

These associations were independent of regular toothbrushing or routine dental checkups—meaning flossing appeared beneficial beyond other oral hygiene practices.

Study Design and Population
The data came from a long-running U.S. cohort study that tracks cardiovascular health and related risk factors. At baseline, participants (mean age early 60s; mixed sex; mostly white, some Black adults) were asked about their flossing frequency, dental care, and other health behaviors. They were free of known cardiovascular disease or arrhythmias at enrollment. Over 25 years, cardiovascular events, stroke subtypes, and arrhythmias were recorded.

Ischemic strokes were further classified: large-artery thrombosis (blockage in a cerebral artery), cardioembolic strokes from the heart, and small-vessel (lacunar) strokes deep in the brain. This classification allowed more precise associations between flossing and specific stroke mechanisms.

For example, the strongest effect was seen for cardioembolic stroke; large-artery and lacunar strokes did not show as strong associations with flossing. This helps pinpoint possible mechanisms.

Biological Plausibility: Why Flossing Might Help
While flossing’s power to freshen breath and prevent cavities is well known, its potential benefits for reducing stroke risk revolve around inflammation, infection, and systemic effects of oral health.

Here’s how the chain might work:

1. Plaque and Gum Infections
   Food debris and bacteria between teeth (especially between teeth and gums) lead to plaque buildup. Poor cleaning upstream promotes gingivitis and periodontitis, which are inflammatory diseases.
   
   
2. Local Inflammation Becomes Systemic
   Gum inflammation isn’t confined to the mouth. Bacteria or their byproducts can enter the bloodstream, triggering broader immune responses and endothelial stress. This can contribute to arterial inflammation, which is a risk factor for stroke.
   
   
3. Atrial Fibrillation Connection
   AFib may be linked to systemic inflammation, oxidative stress, and possibly microbacterial translocation. Since cardioembolic strokes often originate in a heart with AFib, reducing inflammation may reduce both AFib incidence and the risk of clots forming in the heart.
   
   
4. Clot Formation & Vascular Changes
   Reduced systemic inflammation and better oral hygiene may slow down or reduce atherosclerosis progression, reduce clot‐forming potential, and improve vascular health overall.
   

Thus, flossing might act as an upstream mitigation strategy, slowing or preventing harmful processes before they lead to stroke.

Strengths, Limitations, and How to Interpret
Strengths

• Long follow-up (25 years) gives weight to the findings.
  
  
• Large cohort and careful stroke subtype classification allow a more detailed understanding.
  
  
• Adjustment for multiple confounders (including dental visits, brushing, and traditional cardiovascular risk factors) helps isolate flossing as an independent variable.
  

Limitations

• Self-reporting of flossing and oral hygiene behaviors introduces recall bias or overestimation. How accurately people floss or report it may vary.
  
  
• Lack of repeated measurement: Flossing behavior might change over decades, but the study mostly relied on baseline reporting rather than continuous tracking.
  
  
• Preliminary nature: The findings were presented as an abstract at a conference and have not yet been published in full peer-reviewed form. They should guide hypotheses more than definitive practice changes for now.
  
  
• Possible residual confounding: Those who floss may also have other unmeasured healthy behaviors or social determinants (diet quality, health care access, health screening adherence) contributing to lower risk.
  

Thus, while the associations are promising, causation has not been established.

Expert Commentary
Neurologists and cardiologists have reacted with interest. Many say the study reinforces what has been suspected—that oral health is intimately linked with cardiovascular health, beyond just the mouth.

One stroke expert pointed out that while flossing is unlikely alone to prevent strokes in high-risk individuals (e.g. with hypertension, diabetes, or existing cardiovascular disease), it is an additional, low-risk, low-cost habit that adds to cumulative prevention efforts.

Another cardiologist wondered why the effect on large-artery and small-vessel strokes was weaker. If inflammation is the mechanism, then one might expect those stroke types to be impacted too. That discrepancy suggests further research is needed to understand which pathways are most affected.

Clinical Implications: What Doctors Should Do Now
For healthcare practitioners, these findings suggest several actionable considerations:

• Ask about flossing: As part of lifestyle history, inquire about oral hygiene, especially flossing frequency. It may serve as a useful risk marker or point of patient education.
  
  
• Include oral health in cardiovascular counseling: When advising patients with stroke risk factors, include flossing as one of many preventive habits—alongside diet, exercise, blood pressure, cholesterol, and smoking cessation.
  
  
• Encourage minimal thresholds: Even flossing at least once per week showed benefit. While daily flossing remains ideal, this lower threshold may be more achievable for many patients.
  
  
• Collaboration with dental professionals: Encourage coordination between cardiology, neurology, and dental care. Patients with gum disease or poor oral hygiene may benefit from dental referrals as part of stroke prevention.
  
  
• Monitor emerging research: Keep an eye out for full peer-reviewed publications, randomized trials if they occur, or longitudinal studies that measure changes in flossing over time.
  

Public Health & Preventive Messaging
At a population level, the implications are broad:

• Flossing is cheap, easy, and widely accessible—even in resource-limited settings. If confirmed, this habit may offer a “low-hanging fruit” for reducing stroke burden.
  
  
• Public health campaigns may benefit from including oral health in stroke prevention guidelines. Current guidelines tend to emphasize blood pressure, lipids, health behaviors like smoking, but often give oral health only limited attention.
  
  
• Educational programs (community health, primary care, dental hygiene) could emphasize that plaque control and flossing are not just about teeth but about whole-body health.
  
  
• Insurance and policy may begin to support broader oral health screening/control as part of cardiovascular and neurological risk assessment, particularly in older adults.
  

Research Needs: What Comes Next
To turn these findings into stronger clinical recommendations, the following are needed:

1. Peer-reviewed publication of full data: So that the medical community can evaluate methodology, effect sizes, and limitations in depth.
   
   
2. Randomized controlled trials (RCTs): The gold standard would be prospective trials where flossing frequency is altered and outcomes (stroke, AFib, biomarkers of inflammation) are tracked.
   
   
3. Repeated measurement of behavior: To assess whether changing flossing habits later in life changes risk, or if benefits accrue only when done early and consistently.
   
   
4. Mechanistic biomarkers: Studies that measure inflammatory markers, bacterial load, endothelial function, and clotting parameters to map exactly how oral hygiene influences systemic risk.
   
   
5. Population diversity: More data in diverse age, racial, socioeconomic groups to confirm generalizability.
   
   
6. Dose-response: Investigate whether more frequent flossing leads to proportionally greater risk reduction.
   

Broader Implications: Oral Health as Part of brain health
This study adds to a growing landscape of research linking oral health with brain health. Other studies have shown associations between gum disease, tooth loss, and cognitive decline or small vessel disease in the brain. The flossing study now suggests a potentially modifiable behavior that could intersect with both cardiovascular and neurological risk domains.

It reinforces the concept that brain health extends beyond neurology and stroke units—it implicates dental health, primary prevention, and whole-body inflammation. As understanding of “neurovascular health” advances, clinicians may increasingly see oral care as part of neurological care.

Concluding Reflections
While flossing is not a substitute for proven stroke prevention strategies—blood pressure control, cholesterol management, smoking cessation, healthy diet, physical activity—this research suggests that it may be an important add-on with meaningful impact.

Because it’s inexpensive, simple, and already underutilized, promoting even weekly flossing might yield measurable benefits in stroke prevention. For physicians, dentists, and public health officials, the message is clear: oral hygiene matters for more than teeth.