What is this study about? This study focuses on Alzheimer's Disease (AD), a common neurodegenerative disease that affects memory, thinking, and daily life. We aim to explore whether a non-invasive treatment called Repetitive Transcranial Magnetic Stimulation (rTMS) can improve AD symptoms by regulating the "gut-brain-intestine axis" - a connection between gut bacteria, the brain, and the intestines.

Who can participate?

• **AD patients**: Aged 50-80, diagnosed with mild to moderate AD (MMSE score 18-27, MoCA score 10-26), with stable condition for at least 6 months, and able to cooperate with tests and treatment.
• **Healthy controls**: Aged 50-80, with normal cognitive function (MMSE ≥28, MoCA ≥27), no AD family history, and matched in age and gender with AD patients.

Those with epilepsy, severe mental illness, recent use of antibiotics/probiotics, or inability to complete MRI scans are not eligible.

What will participants experience?

• **AD patients**: Will be randomly divided into two groups. Both groups will receive 4 weeks of treatment (5 days/week) with a helmet-like device. One group gets real rTMS (safe magnetic stimulation to the brain), and the other gets sham stimulation (no effective magnetic field, but same sound/feel).
• **Healthy controls**: No treatment, but will complete the same tests as AD patients.
• **Tests during the study**: Cognitive assessments (memory, thinking skills via questionnaires), stool/blood sample collection (to check gut bacteria and body markers), and MRI scans (to look at brain structure/function) at baseline, 1 month, 3 months, 6 months, and 1 year.

What are the potential benefits?

• Free rTMS treatment (for AD patients), free MRI scans (valued at 700 RMB), and a 200 RMB subsidy.
• Free health checks (gut bacteria analysis, metabolic tests) and cognitive evaluations to understand personal health status.
• Contribution to developing new AD treatments that may help future patients.

Is it safe? rTMS is a clinically proven safe technique. Possible mild side effects (headache, scalp irritation) usually go away on their own. Sample collection (stool/blood) and MRI scans are non-invasive or minimally invasive. A professional team will monitor participants throughout to handle any issues.

For healthcare providers This is a multicenter, randomized, double-blind sham-controlled study (200 AD patients, 200 healthy controls). The primary goal is to explore rTMS's mechanism via the gut-brain-intestine axis, with MoCA score changes (6 months post-treatment) as the main outcome. It integrates multi-omics and neuroimaging data to provide evidence for AD's non-drug treatment.

Inclusion Criteria:

• Dementia Patients: Conformed to internationally recognized diagnostic criteria for dementia (e.g., DSM-5, NINCDS-ADRDA)
• Diagnosed through clinical evaluation, neuropsychological scale assessments, and relevant examinations
• Aged ≥50 years and residing in Nanchang, Jiangxi
• With dementia-negative family history, no severe psychiatric or neurological disorders
• No history of major systemic diseases.

Exclusion Criteria:

• Unable to cooperate with all required examinations, intervention procedures, and sample collection during the study.