Gut microbiota alterations and their correlation with constipation in older adults with Alzheimer’s disease or mild cognitive impairment

Previous studies have suggested a link between gut microbiota, constipation and Alzheimer’s disease (AD) as well as mild cognitive impairment (MCI). In this study, we aimed to investigate the changes in the gut microbiota and their relationship with constipation in patients with AD and MCI. A total of 90 participants (30 with AD, 30 with MCI, and 30 normal controls) were recruited from the community-based Nanning Community Elderly Population cohort. We collected fresh fecal samples for analysis and compared the differences in the gut microbiota among the groups. We also categorized these 90 participants into a constipation group and a non-constipation (normal) group using the Rome IV diagnostic criteria, allowing for a comparison of gut microbiota between these 2 groups. There were significant differences in alpha and beta diversity of the gut microbiota among the AD, MCI, and control groups, as well as between the constipation and non-constipation groups. At the genus level, the relative abundance of Lachnospira was decreased in both the AD group and the constipation group, while the relative abundance of Paeniclostridium was increased in both the MCI group and the constipation group. Our findings suggest that changes in the gut microbiota in patients with AD or MCI are partially consistent with those observed in older adults with constipation and may be involved in the pathogenesis of AD.