Measurement and prediction of functional capacity in Alzheimer's disease.

Functional loss in Alzheimer's disease is difficult to measure or predict. The Blessed Dementia Rating Scale (Part 1) correlates well with postmortem changes but is not an effective antemortem index of functional change since disparate behavioral domains are assessed. We performed a factor analysis of the Blessed items in 187 patients with clinically diagnosed Alzheimer's disease and identified 4 independent factors: (I) cognitive, (II) personality, (III) apathy, and (IV) basic self-care. An endpoint, consisting of a score indicative of moderate disability, was determined for each factor. We then used life table analyses to compare the probability of reaching these endpoints over time in longitudinally followed patients. Patients with extrapyramidal signs at their initial visit reached the factor IV endpoint sooner, and those with psychosis or no family history of dementia also reached the factor I endpoint faster. These data illustrate the utility of a multifactorial approach to the assessment of functional capacity in Alzheimer's disease, and also indicate that extrapyramidal symptoms and psychosis are powerful predictors of the rate of decline in basic self-care activities and cognition.