Gut microbiota profiles across intrinsic capacity strata in community-dwelling older adults using full-length 16S...

Intrinsic capacity (IC), introduced by the World Health Organization, provides a multidimensional framework for evaluating functional aging across locomotion, cognition, sensory, psychological, and vitality domains. However, gut microbial features associated with IC among community-dwelling older adults remain incompletely understood. In this exploratory cross-sectional study, we enrolled 52 community-dwelling older adults and assessed gut microbiota using full-length 16S rRNA sequencing. Participants were stratified into IC quartiles, and additional analyses examined composite IC and domain-specific IC scores as continuous measures. Alpha diversity indices were not significantly associated with composite IC after false discovery rate correction, although vitality showed nominal positive associations with observed features and Chao1 richness (both rho = 0.316, P = 0.024, q = 0.288). PERMANOVA did not show statistically robust differences in beta diversity across IC quartile groups using Bray-Curtis distance (R² = 0.061, P = 0.060, q = 0.383), weighted UniFrac distance (R² = 0.083, P = 0.140, q = 0.436), or unweighted UniFrac distance (R² = 0.063, P = 0.211, q = 0.443). Selected bacterial taxa, including Ruminococcaceae, Lachnospiraceae, Alistipes, and Faecalibacterium, showed nominal associations with composite or domain-specific IC measures, but none remained significant after FDR correction or covariate-adjusted regression. In PICRUSt2-predicted functional analyses, several COG features related to transport systems, multidrug efflux, and site-specific recombination were positively associated with the vitality domain after false discovery rate correction. Because functional profiles were inferred from 16S rRNA sequencing rather than directly measured by shotgun metagenomics, metabolomics, or inflammatory biomarkers, these findings should be interpreted as exploratory and hypothesis-generating. This study identifies candidate microbiota and predicted functional features for future longitudinal and mechanistic studies of multidimensional functional aging.