Moderating Effects of Oral Bacteria and Tooth Loss on Cognitive Performance

INTRODUCTION: The oral microbiome may influence brain health and contribute to cognitive decline. However, little evidence exists on the potential modifying role of the oral microbiome in the relationship between tooth loss and cognitive performance. This study aimed to investigate the interaction effects between tooth loss and oral dysbiotic status on cognitive performance. METHODS: Data were from the 2011-2012 National Health and Nutrition Examination Survey. The sample included 677 adults aged 60 to 69 y. Cognitive performance was assessed by the Consortium to Establish a Registry for Alzheimer's Disease, the Animal Fluency Test (AFT), and the Digit Symbol Substitution Test. Significant tooth loss was defined as a loss of ≥10 permanent teeth out of 28. A high dysbiotic index was defined as being in the upper tertile of the ratio of periodontal disease-associated bacteria (Treponema, Porphyromonas, and Tannerella) to healthy bacteria (Rothia and Corynebacterium). RESULTS: A multivariable linear regression model showed a significant interaction effect between tooth loss and dysbiotic index on the AFT (b = -1.87, P = 0.03), indicating that participants with a higher dysbiosis index and fewer missing teeth scored lower on the AFT. CONCLUSIONS: The effect of tooth loss on verbal fluency depends on oral bacterial imbalances: if there is significant tooth loss, bacterial imbalances may not be important. However, when fewer teeth are lost, high bacterial imbalances may account for lower verbal fluency. These findings suggest that maintaining periodontal health aimed at decreasing oral dysbiosis should be promoted among older adults in the community.Knowledge Transfer Statement:Our findings highlight the importance of preserving the health of the teeth and not just retaining the teeth. Oral health awareness and good oral hygiene practice should be further promoted among older adults in the community.