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Oral Bacteria May Influence Cognitive Health in Aging


— January 28, 2025

Study links mouth bacteria to poor cognition, suggesting diet impacts brain function.


A recent study suggests that the bacteria in our mouths may have a surprising impact on our brain health, particularly as we get older. The research shows a possible connection between the bacteria found in the mouth and cognitive functions like memory and attention. Scientists believe that the state of our oral microbiome could play a role in how well we maintain cognitive abilities as we age, even possibly slowing down cognitive decline. This idea has gained interest because around 15% of older adults suffer from mild cognitive impairment, which is a key risk factor for developing conditions like Alzheimer’s disease.

Researchers have already linked poor oral health, like gum disease, to a decline in mental function, but they are now looking deeper into how exactly the mouth and brain may be connected. There are two primary theories. First, harmful bacteria in the mouth could enter the bloodstream and make their way to the brain, potentially causing damage. Second, the oral bacteria responsible for breaking down nitrates in the body, which is needed to create nitric oxide, may be displaced by other harmful bacteria. Nitric oxide is important for brain health because it helps with synaptic plasticity, which is needed for learning and memory.

In the study, 115 participants were examined, including 55 who had mild cognitive impairment. Some participants had a gene variant known as the apolipoprotein E4 allele (APOE4), which is linked to a higher risk of Alzheimer’s disease. The research team analyzed the types of bacteria found in their mouths and how these bacteria correlated with their cognitive abilities. One key finding was that certain types of bacteria seemed to be linked to better brain function. For example, bacteria in the Neisseria genus were found to be associated with better executive function and visual attention in people with mild cognitive impairment, and also with working memory in healthy participants.

Oral Bacteria May Influence Cognitive Health in Aging
Photo by Jason Deines from Pexels

On the other hand, a higher presence of bacteria from the Porphyromonas genus appeared to predict a diagnosis of mild cognitive impairment, while another bacterium, Prevotella intermedia, was found to be linked to the presence of the APOE4 gene. These findings suggest that the oral microbiome may be an important indicator of cognitive health and could potentially be used to identify those at risk for conditions like Alzheimer’s disease.

What’s particularly interesting is that diet seems to play a significant role in shaping the bacteria in our mouths. For example, a diet rich in nitrates — found in foods like leafy greens, beets, and other vegetables — seems to encourage the growth of bacteria that are associated with better cognitive health. This type of diet is commonly found in the Mediterranean diet and the Dietary Approaches to Stop Hypertension (DASH) diet. These diets not only promote heart health but also appear to have a positive effect on brain function, potentially by fostering a healthy oral microbiome.

The research opens up new possibilities for preventing cognitive decline. If scientists can confirm that oral health impacts cognitive health, then improving the health of our mouths could be a simple and effective way to reduce the risk of dementia and other age-related cognitive issues. This could include more attention to oral hygiene or dietary changes that promote a healthier microbiome. Future studies may also explore whether certain treatments, such as prebiotics, can help improve the balance of oral bacteria, possibly providing a way to delay or prevent cognitive decline in older adults.

Overall, while more research is needed to fully understand the connection between oral health and brain health, this study offers a new and promising perspective on the role that bacteria in our mouths might play in aging and cognitive function. It suggests that taking care of our teeth and gums may be more important than we realize when it comes to maintaining our mental sharpness as we age.

Sources:

Study links oral microbiome to cognitive function in older adults

Oral microbiome and nitric oxide biomarkers in older people with mild cognitive impairment and APOE4 genotype

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