To investigate the clinical safety and efficacy of FMT in AD patients, as well as the changes in the gut microbiota of AD patients before and after FMT.

Inclusion Criteria:

• The patients (aged 50-85 years) exhibited cognitive decline persisting for over six months;
• Primarily characterized by recent memory impairment and accompanied by reduced daily living abilities;
• MMSE scores ranging from 3 to 26;
• MRI findings revealed atrophy in the medial temporal lobe, hippocampus, and cerebral cortex, along with widened sulci and fissures.

Exclusion Criteria:

• Patients were excluded if they had severe visual, hearing, or language impairments;
• Tumors;
• hepatic/renal dysfunction.
• with conditions mimicking AD symptoms-such as normal pressure hydrocephalus, vascular dementia (VD or VaD);
• Parkinson's disease dementia (PDD)-were also excluded;
• patients who had participated in clinical drug trials within the past 30 days or consumed folate and vitamin B12 at doses exceeding twice the recommended intake were ineligible.