Alzheimer's Disease Treated With Vagus Nerve Stimulation

Inclusion criteria

• Age: 50-80 years
• Subjects conform to the diagnostic criteria for AD established by the National Institute on Aging and the Alzheimer's Association \[National Institution Aging and Alzheimer's Association (NIA-AA)\]
• There is mild to moderate cognitive impairment, and the clinical cognitive rating scale \[Clinical Dementia Rating (CDR)\] score is 0.5-2.
• Stable use of the drug for more than 1 month, and no plan to change the medication within 6 months after randomization
• The informed consent form is signed, and the patient complies with the requirements.

Exclusion criteria

• Dementia caused by other reasons, including vascular dementia, central nervous system infections (such as AIDS, syphilis, etc.), Creutzfeldt-Jakob disease, Huntington's disease and Parkinson's disease, dementia with Lewy bodies, traumatic brain injury dementia, other physical and chemical factors (such as drug poisoning, alcohol poisoning, carbon monoxide poisoning, etc.), significant physical illnesses (such as hepatic encephalopathy, pulmonary encephalopathy, etc.), intracranial space-occupying lesions (such as subdural hematoma, brain tumor), endocrine system disorders (such as thyroid disease, parathyroid disease), and dementia due to vitamin deficiency or any other cause.
• The presence of a serious or unstable disease, including cardiovascular, liver, kidney, gastrointestinal, respiratory, endocrine, neurological (AD-derived cognitive impairment excluded), psychiatric, immune or blood disorders, and other diseases that the investigator considers may affect the analysis results of this study, or life expectancy \< 24 months.
• A history of cancer within 5 years, except for non-metastatic basal cell carcinoma and/or squamous cell carcinoma, cervical carcinoma in situ, non-progressive prostate cancer, or other cancers with low risk of recurrence or spread.
• The subject has been diagnosed with any primary mental disorder other than AD-related cognitive impairment. If the investigator deems that the presence of this mental disorder or symptom may affect the interpretation of VNS efficacy, cognitive assessment, or the subject's ability to complete the study, then the subject imust be excluded. Subjects with a history of schizophrenia or other chronic psychiatric conditions are also excluded.
• Subjects who are judged by the investigator to have suicidal tendencies
• Illiteracy or insufficient education to complete the scale assessment
• Having a history of alcohol or drug abuse (excluding smoking history) within 2 years prior to the screening visit
• A history of multiple or severe drug allergy, obvious atopic allergic constitution or severe hypersensitivity after treatment (including but not limited to severe polymorphic erythema, linear IgA dermatosis, toxic epidermal necrolysis and/or exfoliative dermatitis) with clinical significance
• Important abnormalities that may be clinically significant and harmful to the subject, affect the study, or suggest other evidence of etiology of dementia during screening, such as physical examination or neurological examination, vital signs, ECG or clinical laboratory test results (determined by the investigator)
• Screening MRI results showing significant abnormalities suggest another potential cause of progressive cognitive impairment, or findings with clinical significance that may affect the participants ability to safely participate in the study. For example, more than two infarcts larger than 2 cm in diameter, infarcts in critical areas such as the thalamus, hippocampus, internal olfactory cortex, parahippocampal cortex, angular gyrus, or other gray matter nuclei in the subcortical regions, as well as a score of \> 2 on the Fazekas Scale
• Any MRI contraindications, including claustrophobia, or the presence of prohibited metal (ferromagnetic) implant/cardiac pacemakers
• There are contraindications for VNS surgery, such as left vagus nerve injury, severe infection at the surgical site, and severe heart, lung, liver, kidney or other system dysfunction that cannot tolerate general anesthesia surgery.
• Currently participating in other interventional clinical trials, or any other type of medical research that is considered scientifically or medically incompatible with this study
• Other reasons that hinder the completion of this study, such as lack of stable caregivers
• Female subjects who are pregnant or planning to become pregnant
• Research center staff members and/or their immediate family members directly related to this study. Immediate family members are spouses, parents, children, or siblings, whether biological or legally adopted relatives.