THE CONSORTIUM TO ESTABLISH A REGISTRY FOR ALZHEIMERS-DISEASE (CERAD).4. RATES OF COGNITIVE CHANGE IN THE LONGITUDINAL ASSESSMENT OF PROBABLE ALZHEIMERS-DISEASE

Reliable information on rate of progression of cognitive impairment in probable Alzheimer's disease (AD) is important for evaluating possibl e beneficial effects of therapeutic agents and in planning long-term c are for patients with this chronic illness. However, wide variability exists in published rates of change for psychometric measures of the d ementing process, and there is need for an accurate analysis of large numbers of persons with the disorder studied over long periods. Utiliz ing the large, well-characterized sample of the Consortium to Establis h a Registry for Alzheimer's Disease and employing a least squares reg ression method to adjust for different levels of impairment and period s of observation, we report rates of change on the Short Blessed Test, Mini-Mental State Examination, Blessed Dementia Scale, Clinical Demen tia Rating, and other cognitive measures in 430 patients with probable AD (mean age at entry = 70.9 +/- 8.0 SD years) studied for up to 4 ye ars. We found that rate-of-change determinations are less reliable whe n the observation period is 1 year or less, that dementia progression may be nonlinear when described by certain measures, and that simple c hange scores do not accurately characterize the rate of decline. We al so found that rate of progression in AD is determined by the severity of cognitive impairment: the less severe the dementia, the slower the rate of decline.