Altered Gut Microbiota in Dementia and Mild Cognitive Impairment in Community‐Dwelling Older Adults in Taiwan

Abstract

AbstractBackgroundThe microbiota‐gut‐brain axis has been implicated in the pathogenesis of dementia. However, research about gut microbiota changes in cognitive impairment remains scarce, and results vary with methodological differences. This study examines biodiversity and the differential abundance of gut flora associated with cognitive impairment in a community‐based cohort of older adults.MethodThe study sample of 298 older adults was derived from a community‐based prospective cohort study, the Epidemiology of Mild Cognitive Impairment in Taiwan (EMCIT). Among them, 82 were ascertained as MCI or dementia. Fecal samples were analyzed by Illumina shotgun metagenomic sequencing. The Metagenomic Phylogenetic Analysis (MetaPhlAn2) pipeline was applied to generate a relative abundance of gut microbiota.ResultIndividuals with dementia or MCI were older (76.6 ± 7.2 years vs. 67.8 ± 6.6 years) and had less education (9.3 ± 4.5 years vs.12.0 ± 3.9 years). There is no significant difference in alpha‐diversity between MCI/dementia and cognitively normal adults after adjusting for age, gender, education, and BMI. However, the PERMANOVA test revealed significant differences in beta‐diversity. The results of linear discriminant analysis (LDA) effect size (LEfSe) showed a differential abundance of taxonomy between the two groups. Increased abundance of several species, including Bacteroides thetaiotaomicron and Ruminococcus torques, and reduced abundance of Prevotella, Eubacterium, and Bifidobacterium were associated with MCI/dementia (Figure 1).ConclusionThe gut microbiota of older adults with MCI/dementia significantly altered in overall diversity and compositions. The mechanism of how altered gut microbiota contributes to the development of dementia needs to be further investigated.