Oral Bacteria Linked to Memory and Alzheimer’s Risk

Study Uncovers Connection Between Mouth Bacteria and Cognitive Function

A recent study conducted by the University of Exeter has shed light on the relationship between oral bacteria and brain health, revealing that certain bacteria may influence memory, attention, and the risk of Alzheimer’s disease. The findings, published on the website SciTechDaily, suggest that specific bacterial groups in the mouth could either support cognitive function or contribute to its decline.

The research, supported by Wellcome and partially funded by the National Institute for Health and Care Research (NIHR) Exeter Biomedical Research Centre, examined how oral microbiomes might impact brain health. According to the study, harmful bacteria could directly enter the bloodstream, potentially affecting the brain. Alternatively, an imbalance between beneficial and harmful bacteria may disrupt the conversion of dietary nitrates—found in vegetables—into nitric oxide, a compound crucial for brain communication and memory formation.

Lead author Dr. Joanna L’Heureux, of the University of Exeter Medical School, 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.”

Beneficial and Harmful Bacteria Identified

The study identified specific bacterial groups associated with cognitive performance. Individuals with higher levels of Neisseria and Haemophilus bacteria demonstrated better memory, attention, and the ability to perform complex tasks. These participants also exhibited elevated levels of nitrite in their mouths, which is linked to the production of nitric oxide.

Conversely, increased levels of Porphyromonas bacteria were more common in individuals experiencing memory problems. Additionally, the bacterial group Prevotella was associated with lower nitrite levels, which researchers predict could indicate poorer brain health. Notably, Prevotella was more prevalent in individuals carrying the APOE4 gene, a known risk factor for Alzheimer’s disease.

These findings suggest that monitoring oral bacteria could serve as a potential tool for early identification of cognitive decline. By integrating bacterial assessments into routine dental checkups, healthcare providers might identify at-risk individuals earlier, enabling timely interventions.

Implications for Mild Cognitive Impairment and Dementia Risk

While some degree of memory decline is typical with aging, significant impairments beyond normal expectations are classified as Mild Cognitive Impairment (MCI). Approximately 15% of older adults fall into this category, which is considered a major risk factor for dementia and Alzheimer’s disease.

The study recruited 110 participants aged 50 and above from PROTECT, an online initiative tracking the brain health of over 25,000 middle-aged individuals in the UK. Participants were divided into two groups: those without cognitive decline and those exhibiting MCI. Mouth rinse samples collected from these groups were analyzed to assess bacterial populations.

Co-author Professor Anne Corbett, also from the University of Exeter Medical School, remarked: “The implication of our research is profound. 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.”

Potential Pathways for Future Research and Interventions

The study’s publication in PNAS Nexus highlights the potential for future research into oral microbiomes and their role in brain health. By understanding how bacterial imbalances affect nitric oxide production and brain function, scientists may develop strategies to mitigate cognitive decline.

Possible interventions could include dietary modifications to boost nitrate intake, the use of probiotics to promote beneficial bacteria, improved oral hygiene practices, or targeted therapies aimed at restoring microbial balance. These approaches could complement existing efforts to address dementia risk factors and improve overall brain health.

The study underscores the importance of interdisciplinary collaboration in addressing complex health challenges. As researchers continue to explore the intricate connections between oral health and cognitive function, the findings offer hope for innovative strategies to support healthy aging.

For further details, the study, titled “Oral microbiome and nitric oxide biomarkers in older people with mild cognitive impairment and APOE4 genotype,” can be accessed via DOI: 10.1093/pnasnexus/pgae543.