Association between microplastics exposure and gut microbiota and metabolites in older adults: A cross-sectional study

BACKGROUND: Microplastics (MPs) pollution is a global issue. Due to long-term accumulation and physiological decline, older adults may be more susceptible to its effects. This study aims to evaluate the associations between MPs and the gut microbiota and metabolites in older adults. METHOD: During the 2024 follow-up of the Ningxia Older Mental Health Cohort, 45 fecal samples were collected. MP detection was performed using laser direct infrared imaging spectrometer (LDIR), and principal coordinates analysis (PCoA) was used to assess microbial community similarity. Wilcoxon tests were used for intergroup comparisons of microbial dysbiosis index (MDI), gut microbiome health index (GMHI), and microbial abundance. Differential metabolites were screened using the orthogonal partial least squares discriminant analysis (OPLS-DA) model and univariate analysis. The Kyoto Encyclopedia of Genes and Genomes (KEGG) database was used for pathway annotation. Bland-Altman analysis evaluated the consistency between fecal MP detection counts and the plastic exposure score (PES) from questionnaires. RESULTS: The average count of MPs in feces was 70.10 particles/g, primarily consisting of polyvinyl chloride (PVC), butadiene rubber (BR), and polyethylene (PE). MP exposure may affect the beta diversity, MDI, and GMHI in older adults. Furthermore, changes in the abundance of certain species in the gut microbiota, such as Klebsiella and Escherichia-Shigella, and levels of metabolites, such as taurine and γ-aminobutyric acid (GABA), were associated with MP exposure. A total of 30 KEGG pathways were significantly enriched, with the primary pathways including taurine and hypotaurine metabolism, and ligand-receptor interaction. MP detection counts show good consistency with PES. CONCLUSION: MP exposure is associated with changes in the characteristics of gut microbiota, microbial abundance, and metabolite levels. PES may serve as a suitable alternative tool for assessing plastic exposure in large populations.