New Alzheimer's Treatments and Diagnosis Study

Inclusion Criteria: 1. Participants must be 19 years of age or older at the time of informed consent. 2. Patients who are undergoing medical evaluation for newly approved Alzheimer's disease medications after 2021, patients who have decided to initiate treatment with these medications in consultation with their physician after 2021, or patients who have already started treatment with newly approved Alzheimer's disease medications after 2021. 3. Patients who have undergone an amyloid PET scan to confirm Alzheimer's disease pathology, or cerebrospinal fluid testing for Aβ42 and ptau181. 4. Clinical diagnosis of Alzheimer's disease, defined as follows: <!-- --> 1. \[Alzheimer's Disease Dementia (ADD)\] - Must meet the criteria for probable Alzheimer's dementia as defined by the National Institute on Aging and the Alzheimer's Association working groups (NIA-AA). * Must exhibit cognitive decline that impairs independent daily living. 2. \[Mild Cognitive Impairment (MCI)\] \- Must meet NIA-AA diagnostic criteria for MCI. \- The subject or informant must report cognitive decline. \- Performance on delayed recall of verbal memory must be more than -1.0 SD below the age- and education-adjusted normative mean, or scores on any one or more tests of executive function, language, visuospatial abilities, or attention must be more than -1.5 SD below the age- and education-adjusted normative mean. \- Clinical Dementia Rating scale (CDR) of 0.5. \- Maintenance of independent daily living ability. \- Not categorized as dementia. 3. \[Cognitively Unimpaired (CU)\] \- Delayed recall of verbal memory must be at or above -1.0 SD versus the age- and education-adjusted normative mean, and all executive function, language, visuospatial abilities, and attention tests must be at or above -1.5 SD versus the age- and education-adjusted normative mean. \- Maintenance of independent daily living ability. * If the subject reports cognitive decline, they will be classified as having Subjective Cognitive Decline (SCD). 5\. Patients must be ambulatory (use of mobility aids is acceptable). 6. The subject must provide written informed consent to participate in the study. In the case of dementia patients, additional written consent from a guardian is required. Exclusion Criteria: 1. Presence of significant psychiatric disorders associated with intellectual disability, schizophrenia, major depression, bipolar disorder, delirium, etc. 2. History of substance abuse or alcohol dependence that required treatment within the past five years. 3. A current diagnosis of cancer that has not achieved remission within the past five years. However, localized prostate cancer, cervical carcinoma in situ, non-melanoma skin basal cell carcinoma, or squamous cell carcinoma are excluded. 4. Evidence of severe or unstable physical conditions (e.g., dialysis, severe liver disease). 5. Visual or auditory impairments that prevent the satisfactory assessment of cognitive function. 6. Inability to perform MRI due to the presence of metallic substances in the body. 7. Currently participating in another drug clinical trial. 8. Currently pregnant or breastfeeding.