Rate of progression of Alzheimer's disease.

We determined rate of cognitive decline in 54 patients with a clinical diagnosis of Alzheimer's disease. Cognitive ability was assessed by score on the Blessed test of orientation, memory, and concentration. Rate of progression was defined as the change in score on the Blessed test per year and was computed using a linear regression analysis. Only patients who had been followed for at least one year and who had at least three separate evaluations were included in the study. The overall rate of progression was 4.1 Blessed points per year. Age of onset, duration of illness, and family history of dementia had no significant influence on rate of progression.