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Introduction: The global population is aging. Although aging populations experience a high burden of dental and systemic diseases, few studies have described the oral microbiota in aging population-based cohorts. This observational, registry-based study aimed to characterize the diversity and composition of the oral microbiota in 1,093 aging Swedes—aged 54–84 years at inclusion—and evaluate associations with host traits, as well as prospective measures of caries and periodontal status.

Methods: Saliva microbiota was characterized using complete 16S rRNA gene sequencing, and dental data were obtained from primary care dental records. Partial least squares regression was used to identify species associated with variation in age, number of teeth, total number of sequence reads, caries, and periodontal status. Follow-up analyses were conducted using two-part regression models with covariate adjustments.

Results: The oral microbiota remained highly diverse in the aging population without major shifts within this age frame. Carriage of hitherto unfamiliar yet well-documented disease-associated species was found to be associated with metrics of active disease but not lifelong measures, such as the common decayed, filled, and missing surfaces index.

Conclusion: These results underscore methodological considerations, including the importance of read number adjustments beyond using relative abundances, and the importance of carefully selecting metrics for oral disease in aging individuals.