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Updated: May 5, 2026

Microbiota Analysis Using Two-step PCR and Next-generation 16S rRNA Gene Sequencing
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The microbiota-gut-brain axis in mild cognitive impairment and Alzheimer's disease: a scoping review of human studies

Alison Warren1, Zan Wynia2, Patrick G Corr1

  • 1The Frame-Corr Laboratory, Department of Clinical Research and Leadership, The George Washington University School of Medicine and Health Sciences, Washington, District of Columbia, USA.

Alzheimer'S & Dementia : the Journal of the Alzheimer'S Association
|January 22, 2026
PubMed

Insights

Gut dysbiosis, an imbalance in gut bacteria, is common in Alzheimer's disease (AD) and mild cognitive impairment (MCI). Interventions targeting the gut microbiome show potential for cognitive health.

Area of Science:

  • Microbiome Research
  • Neurological Disorders
  • Gastroenterology

Background:

  • Alzheimer's disease (AD) poses a significant global health burden.
  • Growing evidence links the gut microbiome to AD pathogenesis.
  • Mild cognitive impairment (MCI) is an early stage often preceding AD.

Purpose of the Study:

  • To conduct a scoping review of gut microbiome research in MCI and AD.
  • To examine the impact of dietary and probiotic interventions on the gut microbiome and cognition.
  • To identify research gaps and future directions in the field.

Main Methods:

  • Searched PubMed, Scopus, and Cochrane Library up to February 2023.
  • Included original research and systematic reviews/meta-analyses (human studies only).
  • Screened 4751 articles, with 58 meeting inclusion criteria using PRISMA-ScR guidelines.

Main Results:

  • Gut dysbiosis frequently observed in MCI and AD.
  • Increased abundance of Pseudomonadota and Actinomycetota in AD.
  • Reduced microbial diversity noted in some MCI/AD cases.
  • Probiotic and dietary interventions showed inconsistent but promising effects on cognition and microbiota.

Conclusions:

  • Gut dysbiosis is a prevalent feature in MCI and AD.
  • Specific microbial shifts are associated with cognitive decline.
  • Interventions modulating the gut microbiota-cognition axis warrant further investigation.
  • Standardized protocols and longitudinal human studies are crucial for causal inference and therapeutic development.
Keywords:
Alzheimer's diseaseMediterraneanbiomarkerscognition disordercognitive dysfunctiondietdysbiosisgastrointestinal microbiomemetagenomicsmicrobiotamicrobiota–gut–brain axismild cognitive impairmentneuroinflammationprobioticsshort‐chain fatty acidssystematic review as topic

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