Oral Microbes Could Influence Your Risk of Cognitive Decline

The bacteria in your mouth affect more than just your teeth and gums—they may also play a role in brain function. A study of 55 people with mild cognitive impairment (MCI) found that those with higher levels of Neisseria bacteria performed better on tests of working memory, executive function, and visual attention. Even among 60 cognitively healthy participants, a Neisseria-dominant oral microbiome correlated with stronger memory.

Led by researchers at the University of Exeter, the study suggests that supporting beneficial oral bacteria could help slow cognitive decline. Probiotics or prebiotics may encourage the growth of these microbes within weeks. These findings align with growing research linking oral health to dementia risk. Scientists have even discovered bacteria from gum disease in the brains of Alzheimer’s patients.

However, not all oral microbes are harmful—some may be protective. Similar to gut bacteria, maintaining a balanced oral microbiome is crucial. Neisseria species, commonly found in the mouth and nose, may offer health benefits, including lowering blood pressure by converting dietary nitrates into nitric oxide. This signaling molecule plays a key role in preventing gum disease, regulating blood pressure, and supporting brain health by enhancing neural plasticity and reducing inflammation—both important factors in Alzheimer’s prevention.

Genetic Risk for Alzheimer’s Linked to Prevotella-Dominant Oral Microbiome

People genetically predisposed to Alzheimer’s often struggle to produce nitric oxide naturally. In this study, molecular biologist Joanna L’Heureux and her team found that among 33 MCI participants with a genetic risk for Alzheimer’s, many had oral microbiomes dominated by Prevotella instead of Neisseria. One species, P. intermedia, strongly correlated with a higher dementia risk, suggesting it could serve as an early disease marker.

Prevotella bacteria appear to use nitrate for their own purposes, reducing the amount available for nitric oxide production. The researchers believe shifting the balance toward Neisseria while limiting Prevotella could improve nitric oxide levels and benefit brain health. Diets rich in nitrates, such as the Mediterranean diet, are already linked to better cognitive function, but further research is needed to explore the connection between diet, the oral microbiome, and key signaling molecules.

A 2021 study found that older adults with Neisseria-dominant microbiomes, along with the related Haemophilus genus, maintained better attention spans, even when dietary nitrate intake varied. Other studies have associated higher Neisseria levels with younger age, lower BMI, healthier teeth, and non-smoking habits.

“Collectively, these results indicate that a high relative abundance of bacteria in the Neisseria–Haemophilus module is linked to better cognitive outcomes in both individuals with MCI and healthy older adults,” L’Heureux and her colleagues concluded.

Read Original Article: Science Alert

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