Composition of the Gut Microbiota in Older Adults Residing in a Nursing Home and Its Association with Dementia.

Alpha diversity was significantly higher in older adults compared with younger individuals.

• Study included 56 older adults residing in a nursing home, of whom 29 had been diagnosed with dementia.
• Gut microbiota composition was characterized by 16S ribosomal RNA (rRNA) gene sequencing.
• Alpha- and beta-diversity metrics were used to assess microbial diversity.
• Analyses adopted covariates as potential confounders including age, sex, frailty status, drug use, and time spent in the nursing home.

Beta-diversity analyses revealed distinct microbial community structures between age groups.

• Beta-diversity analyses were performed alongside alpha-diversity metrics.
• Differences in amplicon sequence variants (ASVs)/features were determined between age groups.
• The study characterized gut microbiota using 16S rRNA gene sequencing across all 56 participants.

In older individuals, Bacteroidota and Proteobacteria were the most abundant phyla, while Firmicutes and Actinobacteriota declined with advancing age.

• Bacteroidota and Proteobacteria were identified as the most abundant phyla in older adults.
• Firmicutes and Actinobacteriota showed declining relative abundance with advancing age.
• These phylum-level changes were detected in nursing home residents using 16S rRNA gene sequencing.

Older adults exhibited an increased relative abundance of Euryarchaeota, a phylum encompassing Archaea predominantly involved in anaerobic carbon dioxide reduction to methane.

• Euryarchaeota encompasses methanogens involved in anaerobic carbon dioxide reduction to methane.
• This increase in Euryarchaeota was observed in older adults residing in the nursing home.
• This finding represents a notable age-associated microbial shift detected in the study population.

Dementia was associated with marked compositional shifts resulting in a distinct microbial signature, including enrichment of Actinobacteriota, Euryarchaeota, and Proteobacteria.

• 29 of the 56 nursing home residents had been diagnosed with dementia.
• Dementia subjects showed significant enrichment of Actinobacteriota, Euryarchaeota, and Proteobacteria.
• Alongside enrichment, depletion of Bacteroidota and Firmicutes was observed in subjects with dementia.
• These compositional shifts resulted in a distinct microbial signature in dementia subjects compared to non-dementia residents sharing the same living environment and diet.

Different bacterial genera mostly belonging to the Firmicutes phylum were associated both with aging and dementia.

• Multiple bacterial genera within Firmicutes were linked to both aging and dementia in the study population.
• These associations were identified after controlling for covariates including age, sex, frailty status, drug use, and time spent in the nursing home.
• The findings were derived from a nursing home cohort of 56 older adults characterized by 16S rRNA gene sequencing.

Age-related remodeling of the gut microbiota included a stable core of common taxa alongside distinct individual-specific signatures reflecting host factors and life-long environmental conditions.

• A stable core of common taxa was identified across older adult participants.
• Distinct individual-specific microbial signatures were also detected.
• The authors concluded these shifts reflect both host factors and life-long environmental conditions.
• Dementia-related changes were suggested to correlate with increased inflammatory species.