How Oral Bacteria May Influence Dementia Risk (New Research)

Most people brush their teeth to avoid cavities and bad breath.

But what if keeping your mouth clean could also help protect your brain? A fascinating new study suggests that certain mouth bacteria might influence cognitive decline—and potentially even dementia risk.

Researchers at the University of Exeter found that people with higher levels of certain bacteria performed better on memory and thinking tests, while others with harmful bacteria were more likely to show signs of mild cognitive impairment (MCI)—a condition that can be an early warning sign for dementia.

This discovery could be groundbreaking, especially for seniors, as dementia rates continue to climb worldwide.

Could regular brushing and flossing be a secret weapon against memory loss?

Here’s what the research reveals.

Scientists studied the oral microbiomes of 120 older adults—half of whom had mild cognitive impairment. They found clear differences in the bacterial makeup of those with cognitive issues versus those with sharp memory and thinking skills.

• People with higher levels of Neisseria and Haemophilus bacteria performed better on cognitive tests.
• Those with more Prevotella intermedia—especially those carrying the APOE4 gene (which increases Alzheimer’s risk)—scored lower on memory and thinking tests.
• The presence of Porphyromonas gingivalis, a bacteria linked to gum disease, was higher in those with MCI.

This means that the bacteria in your mouth aren’t just affecting your gums—they might be impacting your brain, too.

Why does this matter for seniors?

Well, to start, dementia is on the rise—with cases expected to double by 2060, understanding new risk factors is crucial.

And those carrying the APOE4 marker need extra caution. People with this genetic risk factor for Alzheimer’s had higher levels of harmful bacteria, which could put them at even greater risk.

Lastly, oral bacteria impacts the brain’s chemistry. Some bacteria help process nitrate, which is linked to better circulation and brain function. This could explain why certain bacteria were associated with better cognitive performance.

While the study only found associations (not direct proof that bacteria cause cognitive decline), the findings add to growing evidence that oral health and brain health are linked.

The good news? Keeping your mouth clean is one of the easiest ways to take charge of your health.

• Brushing and flossing regularly may help reduce levels of harmful bacteria.
• Seeing a dentist for regular cleanings can help catch early signs of gum disease.
• A healthy diet (rich in leafy greens and nitrates) might encourage “good” bacteria while reducing “bad” bacteria.
• Future research may explore probiotics for oral health, which could offer another way to maintain a balanced microbiome.

Your mouth might be a window into your brain health. The bacteria living in your gums could be influencing your risk for dementia, meaning that taking care of your teeth could be more important than ever.

More research is needed to understand exactly how oral bacteria impact cognitive function, but one thing is clear—keeping your mouth healthy isn’t just about your smile anymore.

So, next time you reach for that toothbrush, remember: you might be protecting your brain as well as your teeth!

To brushing smart and thinking sharp!

Rachel Mace
Managing Editorial Director, e-Alert
with contributions from the research team

P.S. This 60-second oral health tweak makes blood sugar numbers nosedive…

Sources:

Staff, S. (2025, January 30). Bacteria in your mouth could fuel dementia. Study Finds. https://studyfinds.org/oral-bacteria-dementia/