The Alzheimer's Disease Assessment Scale: Evaluation of Psychometric Properties and Patterns of Cognitive Decline in Multicenter Clinical Trials of Mild to Moderate Alzheimer's Disease

Purpose
To evaluate the psychometric properties and patterns of decline on the total score and item scores of the cognitive subscale of the Alzheimer’s Disease Assessment Scale (ADAS-Cog) in patients with Alzheimer Disease (AD).
Methods
We analyzed data from 536 AD outpatients randomized to the placebo group in two identical 26-week multicenter drug trials.
Results
Mean deterioration at week 26 on the ADAS-Cog total score for subjects with moderate dementia was 84% greater than that for those with milder severity (p < 0.001). After adjusting for this effect, age (p = 0.015) and educational level (p = 0.01) also predicted cognitive decline. In a model, absolute change for most individual ADAS items was less than 10% of the possible change, and it was generally smaller than one-third of the standard deviation of the measure. Measurement error variability was greatest for word…

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