Could your oral bacteria predict dementia risk? Scientists uncover surprising brain-health links

Could the bacteria in your mouth predict whether you are at risk of dementia? Emerging research suggests that the bacteria living on your tongue and gums may affect how the brain works and how it changes as we age. In turn, this could affect whether someone ages normally or develops dementia.

Scientists are uncovering surprising connections between the oral microbiome, which is the bustling ecosystem of bacteria in our mouths, and brain health. A new study my colleagues and I conducted suggests that certain bacteria may help memory and thinking skills, while others could be early warning signs of a decline in brain function.

This raises the possibility that diet and treatments that change our oral bacteria could one day play a role in helping to preserve brain health as we age.

For our investigation, we analysed saliva samples from 115 adults over 50 years old. Among these people, 52% had healthy brain function, and the other 48% had early signs of decline in memory and other brain functions.

We examined the bacteria in these samples and showed that people who had large numbers of two groups of bacteria called Neisseria and Haemophilus performed better in brain health tests. In particular, people with these bacteria had better memory, and better ability to pay attention and perform complex tasks.

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These people also had higher levels of the ion nitrite in their mouths. Nitrite is made by bacteria when they break down nitrate, which is a natural part of a vegetable-rich diet.

Bacteria can also break down nitrite to produce nitric oxide, which improves circulation, including blood flow to the brain. This suggests that eating lots of nitrate-rich vegetables, such as leafy green spinach and rocket, could boost levels of healthy bacteria and help improve brain health, which might be especially important as people age.

We are now investigating whether nitrate-rich beetroot juice can improve brain function in older adults by hijacking bacteria in the mouth.

On the other hand, a different group of bacteria may be causing more harm than good. Our study found two groups of bacteria that are potentially linked to worse brain health.

One group called Porphyromonas, which is often associated with gum disease, was more common in people with memory problems than people who were healthy.

A second group called Prevotella was linked to low nitrite, which in turn could mean poorer brain health. Prevotella was also more common in people who carry the gene APOE4, which is associated with an increased risk of Alzheimer’s.

These findings suggest that some bacteria might play a detrimental role in changes in brain health as people age. It also raises the question of whether routine tests to measure levels of these bacteria could be used to detect very early signs of declining brain health as part of dental checkups in the future.

Profound implications

The implications of this research are profound. If certain bacteria support brain health while others contribute to decline, then treatments to change the balance of bacteria in the mouth could be part of a solution to prevent dementia.

Encouraging the growth of nitrite-producing bacteria like Neisseria, while reducing Prevotella and Porphyromonas, could help maintain brain function as we age. This could be achieved through dietary changes, probiotics, oral hygiene routines, or even targeted treatments that reshape the microbiome.

While we’re still in the early stages of understanding the intricate links between the mouth bacteria and the brain, our findings provide a strong rationale for further research.

If future studies confirm that the oral microbiome plays a role in maintaining a healthy brain, then by paying closer attention to the bacteria in our mouths we may unlock new possibilities for detecting and potentially delaying dementia.

In the meantime, the best advice is to keep your teeth clean, see the dentist regularly and eat food with lots of nitrate, like leafy green vegetables, to keep feeding the good bacteria in your mouth.

This article is republished from The Conversation under a Creative Commons license. Read the original article.