Clinical Research Directory

Inclusion Criteria: 1. Age between 55 and 90 years, both sexes eligible; 2. Educational level of primary school or above, or with a sound working history, excluding individuals with intellectual disability; 3. Able to speak Mandarin fluently and capable of completing the full battery of neuropsychological assessments; 4. Geriatric Depression Scale (GDS) score ≤ 6; 5. Adequate visual and auditory function to complete all neuropsychological tests successfully; 6. Willing and able to provide peripheral blood samples and to undergo brain PET and MRI neuroimaging examinations; 7. If taking relevant medications, the dosage must have been stable for at least 4 weeks. Specific medication requirements: stable doses of antidepressants are permitted, provided that the participant has no significant anticholinergic adverse effects and no history of major depressive episode within the past year; estrogen replacement therapy is allowed; Ginkgo biloba preparations may be taken, but routine use is not recommended; use of any psychoactive drugs is prohibited within 4 weeks prior to screening. Exclusion Criteria: 1. Coexisting severe neurological disorders, including Parkinson's disease, multi-infarct dementia, Huntington's disease, normal pressure hydrocephalus, intracranial tumors, progressive supranuclear palsy, epilepsy, subdural hematoma, multiple sclerosis, etc.; history of severe traumatic brain injury with persistent neurological deficits, or history of definite structural brain abnormalities; 2. Brain MRI findings indicating intracranial infection, cerebral infarction, focal organic lesions, or multiple lacunar infarcts in key memory-related brain regions; 3. Contraindications to MRI, such as implanted cardiac pacemakers, or the presence of metallic foreign bodies or fragments within the body; 4. Diagnosis of major depressive disorder or bipolar disorder according to DSM-5 criteria within the past 1 year; presence of psychotic symptoms, agitation, or aggressive behavior within the past 3 months that would preclude compliance with the study protocol; 5. Past history of schizophrenia, or current pharmacotherapy for obsessive-compulsive disorder or attention deficit disorder; 6. History of alcohol or substance abuse or dependence meeting DSM-5 criteria within the past 2 years; 7. Concomitant severe systemic diseases or unstable general medical conditions that would preclude participation in the longitudinal follow-up of this study; 8. Clinically significant abnormalities in serum vitamin B12 or thyroid function indicators, with direct exclusion for those presenting with decreased vitamin B12 levels; 9. Current use of psychoactive drugs, including antidepressants, neuroleptics, long-acting anxiolytics, or sedative-hypnotics; long-term use of anticoagulants such as warfarin, dabigatran, rivaroxaban, or apixaban (except for lumbar puncture procedures); 10. Concurrent participation in other neuropsychiatric clinical studies.