Oral Microbiome Changes in the Correlation Between Periodontal Disease and Cognitive Decline
As for the gut microbiome, the composition of the oral microbiome appears to change with age. The oral microbiome receives less attention than the gut microbiome, but the same scientific tools can be used to correlate specific changes with specific age-related conditions. Here, researchers correlate abundance of specific microbial species with the existing known relationship between periodontal disease and manifestations of neurodegeneration, such as loss of cognitive function. One mechanism that likely contributes to these associations is the contribution of the oral microbiome to chronic inflammation, when microbes and microbial metabolites leak into circulation via damaged gums, but the size of the effect remains debated, and there are other possible mechanisms to consider as well.
Emerging evidence implicates the oral-brain axis in neurodegeneration, yet large community-based studies remain limited. This study aimed to examine associations between periodontal health, oral microbiome, and cognitive performance, and to explore potential biological pathways underlying these relationships. We conducted a cross-sectional analysis of 1,157 participants from the community-based Taizhou Imaging Study, all of whom underwent comprehensive periodontal examinations, salivary microbiome profiling, and cognitive assessments. Periodontal health and microbiome features were treated as exposures, and cognitive performance as the outcome.
Five clinical periodontal indices were found to be inversely associated with cognitive performance. Ten microbial genera (e.g., Haemophilus), 21 functional pathways (e.g., FoxO signalling), and two co-abundance modules, including a Treponema module, were significantly related to cognitive function. Mediation analysis suggested that 11 features, including nitrate-reducing taxa and a Treponema-driven inflammatory module, may partially mediate the relationship between periodontal health and cognition. These community-based findings reveal microbiome-mediated links along the oral-brain axis and highlight periodontal health and oral microbial homoeostasis as potential targets for early prevention of cognitive decline.