Association between gut microbial dysbiosis and Alzheimer’s disease: an umbrella review

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder that primarily affects the elderly, leading to memory loss, cognitive decline, and a gradual deterioration of functional abilities. Traditionally, AD research has focused on amyloid-beta plaques and tau protein tangles. However, in recent years, increasing attention has been given to the role of gut microbial dysbiosis, an alteration in gut microbial communities, in contributing to cogitative impairment. This umbrella review aimed to explore the association between gut microbiota changes and AD by reviewing and findings from existing systematic reviews (SRs). A comprehensive literature search was conducted across databases, including MEDLINE, Scopus, Embase, Google Scholar, and Web of Science up to January 10, 2025, following PRISMA guidelines. Data from eligible SRs were extracted using the CADIMA platform, and the risk of bias was assessed. Twelve SRs met the inclusion criteria. Seven reported descriptive findings linking gut microbial changes with AD pathogenesis and five studies included quantitative data revealing increased abundance of Firmicutes and Proteobacteria in individuals with AD, implicating gut dysbiosis in its pathophysiology. Overall findings suggest that specific shifts in microbial composition could influence the onset and progression of AD, highlighting the gut microbiota as a potential target for therapeutic interventions.