Objective: To determine rates of decline in Alzheimer's disease.
Design: A longitudinal review of patients diagnosed as having dementia during life, tested serially with the Extended Scale for Dementia, and confirmed by autopsy as having Alzheimer's disease.
Subjects and setting: Twenty-nine dead patients with Alzheimer's disease from the participants in the University of Western Ontario Dementia Study Project, confirmed at autopsy as having Alzheimer's disease.
Methods: Analysis of the Extended Scale for Dementia data according to a trilinear model.
Findings: In the middle phase of the trilinear model, there was a mean annual change of 13% (range, 2.5% to 51.7%).
Conclusions: It is likely that the common method of averaging a group of different individual scores from the initial and middle phases of observation of Alzheimer's disease collapses together individuals at different stages of the disorder, some of whom are in the initial plateau phase and whose conditions are not declining rapidly. The trilinear model of decline avoids this difficulty and the present study provides postmortem confirmed figures on rate of change.