Differences in oral microbiota between elderly and adults: A systematic review

The aging process may significantly impact bacteria in the oral cavity (oral microbiome), leading to notable changes in its diversity and composition, potentially influencing systemic health. This systematic review aimed to compare the oral microbiota of elderly individuals (≥60 years) with that of younger adults.

A comprehensive search of PubMed, Medline, EMBASE and CINAHL identified 794 studies published between 2005 and May 2023. Studies were included if the investigators compared the oral microbiome of elderly with younger adults using 16S rRNA sequencing. The JBI Critical Appraisal Checklist for Analytical Cross-Sectional Studies was employed to evaluate risk of bias. Ten full-text articles met the criteria for inclusion.

The included studies revealed inconsistent results regarding alpha and beta diversity and the abundance of bacterial phyla with aging. Some studies reported increased diversity or abundance, others showed decreases, and several found no significant differences. However, this review identified a consistent decline in the abundance of Haemophilus, Granulicatella, and Veillonella, alongside an increase in Comamonas, in elderly populations across multiple studies. These genera may play critical roles in maintaining oral health and microbial stability in elderly populations, highlighting the need for further investigation.

The variability in microbial diversity and abudance suggests that confounding factors such as oral hygiene, systemic health, medication use, and lifestyle may complicate interpretation of results. In conclusion, future research should employ longitudinal designs with standardized methodologies and address confounding factors to better understand the aging oral microbiome and its implications for healthspan and quality of life.