'How far' vs 'how fast' in Alzheimer's disease. The question revisited

Abstract

Objective: To expand on a recent study of 42 patients with probable Alzheimer's Disease that found that the only significant predictors of certain clinical end points were the degree of severity features at entry ("how far").

Design: A case series study of a cohort of 81 patients with Alzheimer's disease that used survival analysis methods similar those of the previous study but included a new technique for calculating rate of progression ("how fast") as well as entry characteristics ("how far").

Setting: A university medical center and its affiliated Veterans Affairs Medical Center.

Patients: All patients with probable and definite Alzheimer's disease studied at the Aging Clinical Research Center at Stanford University, Palo Alto, Calif, in the years 1981 and 1992 who met the following criteria: a mild to moderate level of severity of the disease (Mini-Mental State Examination score of 15 or above) at entry into the study and a minimum of three test points spaced approximately 6 months apart (to allow estimation of rate of progression). A total of 81 such patients were identified. These patients had been followed up for a mean of 4.53 +/- 2.3 years, with a range of 1.0 to 14.5 years.

Main outcome measure: The outcome measure was the average rate of decline on the Mini-Mental State Examination.

Results: The results of our study replicated a previous finding that the degree of severity is a strong predictor of time course, but in addition we found that the rate of progression also appears to be a strong predictor of clinical course.

Conclusion: There appears to be substantial heterogeneity in the rate of progression in patients with Alzheimer's disease, and, like initial degree of severity, rate of progression appears to be a strong predictor of clinical course.