Oral microbiota associated with tooth loss and cognitive function in older adults: Evidence from NHANES

BACKGROUND: The aim of this study is to investigate the association between tooth loss and cognitive decline and to explore the potential role of salivary microbial genera in this relationship in a nationally representative population. METHODS: Data from 1,413 adults aged ≥ 60 years in NHANES 2011-2012 were analyzed. Cognitive function was assessed using the Consortium to Establish a Registry for Alzheimer's Disease (CERAD) Word Learning Tests, the Animal Fluency Test (AFT), and the Digit Symbol Substitution Test (DSST). Salivary microbiome profiles were obtained from a subsample of 661 participants using 16S rRNA sequencing. Complex survey regression, PERMANOVA, and multivariable microbial association analyses were applied. Mediation analyses were conducted as exploratory analyses to evaluate potential microbial pathways linking tooth loss with cognitive outcomes. RESULTS: Moderate tooth loss was associated with higher odds of low global cognition (OR = 2.91, 95%CI: 2.01-4.23), low AFT (OR = 1.57, 95%CI: 1.03-2.39), and low DSST (OR = 2.15, 95%CI: 1.47-3.16) after adjustment. Sixteen genera were associated with at least one cognitive metric, including Prevotellaceae_NA, Phocaeicola, and Lactobacillus. In exploratory mediation analyses, three organic acid-producing genera (Lactobacillus, Lachnospiraceae_NA, and Leptotrichiaceae_NA) were identified as potential contributors to the association between tooth loss and cognition. CONCLUSION: Tooth loss was associated with cognitive decline in older adults, and both conditions were accompanied by differences in salivary microbial composition. Exploratory mediation analyses suggested that certain organic acid-producing taxa may contribute to the observed association. PLAIN LANGUAGE SUMMARY: Tooth loss is common in older adults and has been linked to problems with memory and thinking, but the reasons for this connection are not fully understood. In this study, we used data from a large national health survey of adults aged 60 years and older to examine tooth loss, results from several cognitive tests, and the types of bacteria found in saliva. We found that older adults with more missing teeth were more likely to perform poorly on tests measuring memory, attention, and processing speed. We also observed that some types of oral bacteria were related to both tooth loss and cognitive performance. In exploratory analyses, several groups of bacteria that produce organic acids were linked to the relationship between tooth loss and cognitive outcomes. These findings suggest that differences in the oral microbial community may be one of several biological pathways connecting oral health and cognitive function. Understanding how oral health, diet, and oral bacteria interact may help researchers better understand factors related to cognitive aging and to identify potential targets for future research and prevention strategies.