Older Adults’ Saliva Showed Microbial Shifts Tied to Higher Caries Risk

Posted: October 8, 2026

Older Adults’ Saliva Showed Microbial Shifts Tied to Higher Caries Risk

Edited by Hygienetown staff

Older adults had higher salivary levels of mutans streptococci and a less diverse oral microbiome than adolescents and younger adults, according to a cross-sectional study published online Oct. 4 in the Journal of Dentistry.

Researchers at Hiroshima University Hospital in Japan compared 229 people ages 12–35 with 111 people ages 50 and older. All underwent caries risk testing with stimulated saliva at the hospital’s Oral Examination Center between February 2022 and September 2025.

Testing measured salivary secretion volume, pH, and buffering capacity, along with cultures of mutans streptococci, Lactobacillus, and Candida species. DMFT index and plaque control records came from patients’ medical records.

Mutans streptococci levels and salivary buffering capacity were both significantly higher in the older group, at P less than .05.

For the microbiome analysis, investigators sequenced bacterial DNA from a randomly selected subset of 30 younger and 58 older participants. Microbial diversity was lower in the older group, and Prevotellaceae and Actinomycetota were among its most prevalent bacteria. Pathway analysis showed elevated expression of genes involved in anaerobic and glucose metabolism in the older participants.

The authors concluded that age-related ecological shifts in the oral microbiome may increase the risk of dental caries. They noted that caries prevalence is rising among older individuals while reports on this population’s dental health remain limited.

Yuka Hayashi-Okamura, Tomoaki Shintani, Mikihito Kajiya, and colleagues conducted the study. The authors declared no competing interests.

Because the design was cross-sectional, the study cannot establish that the microbial differences cause caries. Sequencing covered only a subset of participants, and all were tested at a single hospital center.

Sources:
Journal of Dentistry, “Age-related shifts in the salivary microbiome linked to cariogenic changes: A cross-sectional study,” published online Oct. 4, 2026:
doi.org/10.1016/j.jdent.2026.107091
PubMed, PMID 42830139:
pubmed.ncbi.nlm.nih.gov/42830139


Older Adults’ Saliva Showed Microbial Shifts Tied to Higher Caries Risk

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