SYSTEMATIC REVIEW article
Front. Neurosci.
Sec. Gut-Brain Axis
This article is part of the Research TopicThe Impact of Diet on Alzheimer's DiseaseView all 3 articles
The Correlation and Gut Microbial Characteristics in the Whole Spectrum of Alzheimer's Disease: a Systematic Review and Meta-analysis
Provisionally accepted
Zhen Wang1,2*
JINGRONG CAO3*
Xiaoyi Zhao3Haixiao Li4
Houjian Ren1,2
Wenya Zhang5Jie Fan6Han Song4Defeng Wang6- 1hebeigongcheng, Handan, China
- 2Hebei University of Engineering School of Medicine, Handan, China
- 3Department of Clinical Laboratory, Xiongan Xuanwu Hospital, Xiongan Xuanwu Hospital, Baoding, China
- 4Xiongan Magic Medical Laboratory, Xiongan Xuanwu Hospital, Baoding, China
- 5Hebei Medical University School of Basic Medicine, Shijiazhuang, China
- 6Affiliated Hospital of Hebei Engineering University, Handan, China
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Background: Gut dysbiosis is hypothesized to be a potential pathological mechanism in patients across the Alzheimer's disease (AD) spectrum. Nevertheless, despite growing interest, existing findings remain largely inconsistent. Purpose: This systematic review and meta-analysis aimed to compare the composition of gut microbiota (GM) between patients with mild cognitive impairment (MCI) or AD and healthy controls (HC). Methods: PubMed, Embase, MEDLINE and Web of science were searched from January 2022 to November 2025. Eligible studies included observational studies and pre-intervention arms of interventional trials reporting GM abundance in AD spectrum patients vs. HC. Two reviewers independently screened articles, extracted data, and assessed bias risk. Effect sizes were pooled using an inverse-variance weighted random-effects model. Results: Twenty studies (1,025 HC and 456 AD spectrum patients) were analyzed. AD patients demonstrated reduced GM diversity vs. HC cohort. The abundances of Megamonas and Bacteroides were elevated in AD patients, while Firmicutes and Proteobacteria were reduced. When stratified by clinical stage, Fusobacteria and Lactobacillus abundances showed gradient shift from MCI to AD. Conclusions: Individuals within the AD spectrum exhibit altered GM abundance, with these differences influenced by clinical stage. The present study did not identify any significant trends; it reports only findings that have been statistically substantiated.
Keywords: Alzheimer's disease, Gut Microbiota, healthy controls, Meta-analysis, Mild Cognitive Impairment
Received: 23 Jan 2026; Accepted: 13 Feb 2026.
Copyright: © 2026 Wang, CAO, Zhao, Li, Ren, Zhang, Fan, Song and Wang. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence:
Zhen Wang
JINGRONG CAO
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