Oral Microbiome Composition Linked to Brain Health in Aging Adults, Exeter Study Finds

A University of Exeter-led study has uncovered potential connections between oral bacteria and cognitive function in older adults. The research, published in PNAS Nexus, suggests that certain bacteria in the mouth may influence brain health as people age, with some associated with better cognitive performance and others linked to increased risk of Alzheimer's disease.

The study examined 110 participants over 50 years old, divided into groups with and without mild cognitive impairment. Researchers analyzed mouth rinse samples to study bacterial populations and their potential impacts on brain function. Two key mechanisms were identified: harmful bacteria potentially entering the bloodstream and damaging the brain, and bacterial imbalances affecting the conversion of nitrate to nitric oxide, a chemical crucial for brain communication and memory formation.

Specific findings revealed that higher levels of Neisseria and Haemophilus bacteria were associated with better memory, attention, and complex task performance. Conversely, Porphyromonas bacteria were more common in individuals with memory problems. Prevotella bacteria were linked to low nitrite levels and more prevalent in carriers of the APOE4 Alzheimer's risk gene.

Joanna L'Heureux, lead author of the study, stated, "Our findings suggest that some bacteria might be detrimental to brain health as people age. It raises an interesting idea for performing routine tests as part of dental checkups to measure bacterial levels and detect very early signs of declining brain health."

Co-author Anne Corbett added, "If certain bacteria support brain function while others contribute to decline, then treatments that alter the balance of bacteria in the mouth could be part of a solution to prevent dementia. This could be through dietary changes, probiotics, oral hygiene routines, or even targeted treatments."