The goal of this prospective, multicenter, observational cohort study is to evaluate the screening performance of blood-based biomarkers for Alzheimer's disease (AD) in a real-world community screening setting, and to establish the population baseline levels and reference intervals of these biomarkers in Chinese older adults.

The main questions it aims to answer is:

What is the clinical screening value of blood biomarkers (phosphorylated tau 217 to amyloid β 42 ratio [pTau217/Aβ42] and glial fibrillary acidic protein [GFAP]) for AD among community-dwelling older adults? Eligible study participants will be randomly enrolled from community-dwelling older adults undergoing routine physical examinations and outpatient clinic attendees. All enrolled participants will undergo AD screening via blood biomarker testing. Participants with positive blood biomarker results (defined as abnormal pTau217/Aβ42 ratio and/or GFAP levels) will further complete a full battery of cognitive scale assessments, including the Mini-Mental State Examination (MMSE), Montreal Cognitive Assessment (MoCA), Activities of Daily Living (ADL) scale, and 17-item Hamilton Depression Rating Scale (HAMD-17). In addition, 15% of participants with negative blood biomarker results, selected via random sampling, will also complete the same cognitive scale assessments.

Inclusion Criteria:

• Aged 60-80 years
• Capable of normal communication and able to complete the questionnaire

Exclusion Criteria:

• Severe mental disorders
• Severe visual, auditory, comprehension or mobility impairments
• Current participation in other health intervention clinical studies
• Severe renal insufficiency, heart failure, cerebrovascular disease, anemia, hyperthyroidism, hypothyroidism
• Multiple cerebral infarctions, severe white matter hyperintensities, history of cerebral hemorrhage, current anticoagulant use, MRI abnormalities (cortical iron deposition, cerebral contusion)
• Unable to comply with study procedures with no legal guardian

Community-dwelling Chinese older adults recruited from community physical examination and outpatient settings across 4 multicenter sites, who voluntarily participate in Alzheimer's disease screening and meet the study's eligibility criteria.