Can Your Oral Microbiome Influence Cognitive Decline?

The Surprising Link Between Your Oral Microbiome and Cognitive Decline

How the Bacteria in Your Mouth May Be Impacting Your Brain

For decades, medical professionals have understood the critical role that oral health plays in systemic diseases such as diabetes, heart disease, and even respiratory infections. However, new research suggests that the bacteria residing in your mouth may also influence cognitive function and the risk of neurodegenerative disorders such as Alzheimer’s disease.

A recent study conducted by researchers at the University of Exeter, UK, investigated the connection between oral bacteria and brain function. Their findings revealed a strong correlation between the presence of specific bacterial species in the mouth and cognitive performance—a revelation that could pave the way for novel interventions to slow cognitive decline.

The Study: Neisseria and Cognitive Function

The study examined 55 individuals diagnosed with mild cognitive impairment (MCI) and compared them to 60 cognitively healthy individuals. The results were striking: participants with a higher abundance of Neisseria bacteria in their mouths demonstrated better working memory, executive function, and visual attention. The positive effects of Neisseria dominance were also observed in healthy individuals without cognitive decline, further reinforcing the idea that the oral microbiome plays a crucial role in brain health.

The Microbiome-Brain Connection: How Oral Bacteria Influence Neurological Health

The Neisseria genus, which includes more than 20 different species, is a natural inhabitant of the nose and mouth. Unlike harmful bacteria linked to periodontal disease, Neisseria is associated with a range of beneficial health effects, including improved cardiovascular function.

One of the key benefits of Neisseria is its ability to convert dietary nitrates into nitric oxide (NO). Nitric oxide is a vital signaling molecule that regulates blood pressure, enhances cardiovascular function, and supports neural plasticity.

• Nitric Oxide and Brain Function: Several studies have suggested that nitric oxide plays a crucial role in preserving cognitive function. It is thought to reduce neuroinflammation, improve synaptic transmission, and enhance overall neural efficiency—all of which are essential factors in preventing neurodegenerative diseases.
• A Key Factor in Alzheimer’s Disease? Intriguingly, individuals who are genetically predisposed to Alzheimer’s disease have been found to have reduced nitric oxide production. This raises the possibility that promoting Neisseria bacteria in the oral cavity could enhance nitric oxide bioavailability and potentially slow cognitive decline.

The Role of Harmful Bacteria: The Prevotella Connection

While some bacteria, like Neisseria, may be protective, others appear to contribute to cognitive decline. The study found that individuals with an elevated genetic risk for Alzheimer’s disease had higher levels of Prevotella bacteria in their mouths.

One species in particular, Prevotella intermedia, was identified as a predictor of increased dementia risk. Researchers speculate that Prevotella competes with Neisseria for nitrate, thereby reducing the availability of nitric oxide and exacerbating neuroinflammation—a major driver of Alzheimer’s pathology.

Can Modifying the Oral Microbiome Reduce Dementia Risk?

If the findings of this study hold true in larger trials, modifying the oral microbiome could become a viable strategy for reducing cognitive decline and delaying neurodegenerative diseases.

• Probiotics and Prebiotics: Future interventions may include probiotic and prebiotic supplements designed to boost Neisseria levels while suppressing harmful bacteria like Prevotella.
• Dietary Changes: A diet rich in nitrate-containing foods, such as leafy greens, beets, and root vegetables, has already been associated with improved cognitive function. The Mediterranean diet, known for its high nitrate content and anti-inflammatory properties, could be particularly beneficial in maintaining a healthy oral and gut microbiome.
• Oral Hygiene Practices: Brushing, flossing, and using antibacterial mouth rinses may also help modulate bacterial populations, although excessive use of antibacterial agents could disrupt beneficial microbes.

Further Research is Needed

While this study adds to the growing body of evidence linking oral health to brain function, more research is required to determine the precise mechanisms involved.

A 2021 study found that in healthy older adults, a Neisseria-dominant microbiome was associated with improved cognitive function, even when dietary nitrate intake varied. Other research has linked higher Neisseria levels to younger age, lower BMI, and fewer damaged teeth—all factors associated with better health outcomes.

Takeaway: Oral Health and brain health Are Closely Linked

This study highlights an emerging oral-brain axis that may help explain why poor oral health is consistently linked to an increased risk of dementia. If these findings continue to be validated, simple interventions targeting oral bacteria may become a key part of dementia prevention strategies in the future.

Maintaining good oral hygiene, following a nitrate-rich diet, and considering probiotics targeting oral bacteria could soon become mainstream recommendations for brain health.