A recent study has revealed that bacteria in the mouth may have a surprising influence on cognitive function as we age. Published in PNAS Nexus, the research suggests that certain harmful bacteria could play a role in the development of memory loss and dementia, including Alzheimer’s disease. This new insight into the connection between oral health and brain function is drawing attention to the need for better oral hygiene as a potential means of protecting against cognitive decline.
The study analyzed the oral microbiome of 115 individuals, including 55 with mild cognitive impairment, a condition that often serves as a precursor to dementia. Researchers discovered that some bacteria, such as Porphyromonas, were associated with a higher risk of mild cognitive impairment, while others, like Neisseria, were linked to better cognitive performance, such as stronger working memory and executive function.
Additionally, the study found that the presence of Prevotella intermedia was associated with a higher likelihood of carrying the apolipoprotein E4 (APOE4) allele, a genetic variant that increases the risk of Alzheimer’s disease. Researchers also noted that diet plays a significant role in shaping the oral microbiome. Diets rich in nitrates, like the Mediterranean or DASH diets, appear to support beneficial bacteria that promote cognitive health.
James Giordano, Ph.D., a neuroscientist from Georgetown University Medical Center, commented on the study’s implications for brain health, explaining that the presence of specific bacteria in the mouth can contribute to the production of nitric oxide (NO), a chemical that plays a critical role in brain function. NO has been shown to regulate cerebrovascular tone and support neural functions essential for cognitive processing. Furthermore, nitric oxide may help protect against neuroinflammation, a key factor in cognitive decline.
On the other hand, harmful oral bacteria, such as Porphyromonas gingivalis, Treponema denticola, and Prevotella intermedia, may contribute to neuroinflammation. When these bacteria enter the bloodstream, they can travel to the brain, especially in people with Alzheimer’s, whose blood-brain barrier becomes more permeable. This can potentially accelerate cognitive decline by fostering an inflammatory environment in the brain.
This connection between oral health and brain health underscores the importance of maintaining good oral hygiene to reduce the risk of cognitive issues. Gum disease, or periodontitis, is already known to be linked to cognitive decline, and this study strengthens the case for oral health as a factor in overall brain function.
Jennifer Bramen, Ph.D., a senior research scientist at the Pacific Neuroscience Institute, also weighed in, emphasizing that incorporating nitrate-rich foods, such as vegetables, into one’s diet can help promote a healthy oral microbiome and, in turn, support both oral and cognitive health.
This study also points to the potential for future research aimed at identifying specific oral microbiome markers that could serve as early indicators of brain health, as well as the possibility of supplementing or restoring beneficial oral bacteria to prevent or mitigate neuroinflammation and cognitive decline.
