Exploratory Clinical Study and Validation of Blood Biomarkers for Alzheimer's Disease

Inclusion Criteria: For All Participants (HV and AD groups): * Age between 50 and 85 years * Ability to understand and sign informed consent * Availability for the full duration of the study (24 months) * Fasting capability for morning sample collection (between 8:30-12:00) * Willingness to provide blood and urine samples for biomarker analysis and biobank storage Additional Criteria for Healthy Volunteers (HV): * No history or current diagnosis of neurodegenerative disease * Normal cognitive function confirmed by neuropsychological testing (e.g., MMSE score within normal range) * No significant abnormalities on brain imaging (CT or MRI if performed) * No use of medications affecting cognitive function Additional Criteria for Alzheimer's Disease Patients (AD): * Clinical diagnosis of probable Alzheimer's disease based on standardized criteria * Cognitive impairment confirmed by neuropsychological testing (e.g., MMSE score below threshold) * Supporting evidence from brain imaging (CT or MRI) and/or cerebrospinal fluid biomarkers (if available) * Stable medical condition allowing participation in study procedures Exclusion Criteria: For All Participants: * History of major psychiatric disorders (e.g., schizophrenia, bipolar disorder) * Significant neurological conditions other than Alzheimer's disease (e.g., Parkinson's disease, stroke) * Active malignancy or history of cancer within the past 5 years (except localized skin cancer) * Severe renal, hepatic, or cardiovascular disease * Current participation in another interventional clinical trial * Known blood disorders or conditions affecting red blood cell morphology or function * Recent blood transfusion (within 3 months) * Substance abuse or alcohol dependence * Inability to comply with study procedures Additional Exclusion for Healthy Volunteers: * Any cognitive complaints or subjective memory loss * First-degree family history of Alzheimer's disease (optional, depending on stratification strategy) * Use of psychoactive medications Additional Exclusion for Alzheimer's Disease Patients: * Diagnosis of mixed or atypical dementia * Rapidly progressive cognitive decline suggestive of other pathology * Contraindications to lumbar puncture (if CSF sampling is planned)