Biomarker-based Alzheimer's Disease Cohort Study (BASIC)

The event of conversion from mild cognitive impairment to dementia within three years. Cognitive status will be assessed using Clinical Dementia Rating scale-Global Score (CDR-GS): mild cognitive impairment: CDR-GS = 0.5; dementia: CDR-GS > 0.5.

The Hachinski Ischemic Score (HIS) is a brief 13-item scale (range 0-18) in which scores ≤4 favor Alzheimer's disease and ≥7 suggest vascular dementia, based on clinical features such as abrupt onset, vascular risk factors, and focal neurological signs.

Immediate Recall assesses short-term auditory-verbal memory by recording the number of words correctly repeated after a single presentation (typically 0-15); lower scores indicate poorer encoding.

Digit Span Test quantifies auditory-verbal working memory via the longest sequence of digits correctly repeated forward (attention) and backward (manipulation); score = maximum span length.

Trail Making Test (TMT) measures processing speed and executive function via completion time (seconds) for Part A (number sequencing) and Part B (alternating numbers-letters); higher scores indicate poorer performance.

Boston Naming Test quantifies confrontation naming ability by the number of spontaneously correct responses; lower scores indicate lexical-semantic impairment.

Delayed Recall quantifies the number of previously learned items correctly reproduced after a ≥20-minute unfilled interval (range 0-15); lower scores signal impaired consolidation.

Cued Recall evaluates the number of previously learned items correctly retrieved following semantic prompts (range 0-15); lower scores reflect deficient retrieval efficiency.

Subjective Cooperation Score is a single-item rater judgment (0-10 scale) quantifying participant engagement and compliance during cognitive testing; higher values denote greater cooperation.

The Neuropsychiatric Inventory (NPI) is a validated informant-based scale assessing 12 neuropsychiatric domains (range 0-144); higher scores denote greater symptom frequency and severity.

The 15-item Geriatric Depression Scale (GDS-15) is a self-report screen for depressive symptoms in older adults; total score 0-15, with ≥5 indicating probable depression.

Daily and Overall Functional Assessment quantifies independence in basic and instrumental activities of daily living (ADL/IADL) via standardized informant or performance-based scales; higher scores denote greater functional ability.

The Activities of Daily Living (ADL) Scale is a brief, validated instrument that rates independence in basic self-care tasks; scores range from 0 (total dependence) to 6 (full independence), with lower values indicating greater functional impairment.

The events of transitioning from mild dementia to moderate dementia, and from moderate dementia to severe dementia.Cognitive status will be assessed using Clinical Dementia Rating scale-Global Score (CDR-GS): mild cognitive impairment: CDR-GS = 0.5; moderate dementia: CDR-GS = 2; severe dementia: CDR-GS = 3.

Amyloid-beta (Aβ), tau, neurofilament light chain protein (NFL), brain-derived neurotrophic factor (BDNF), glial fibrillary acidic protein (GFAP), and markers related to chronic inflammation, etc.

Structural imaging and functional imaging.

Power of each EEG frequency band

Brain metabolic imaging and amyloid imaging

Routine and biochemical analysis of cerebrospinal fluid (CSF), as well as the measurement of Aβ and tau proteins