Rate of Decline in Alzheimer Disease Measured by a Dementia Severity Rating Scale

Abstract

To measure clinically relevant change in Alzheimer disease (AD) using a family member-completed Dementia Severity Rating Scale (DSRS) questionnaire. Measuring rate of change provides important clinical information. Most neuropsychologic scores change nonlinearly, complicating their use as a predictor of change throughout the illness. DSRS and Mini Mental State scores were prospectively collected on 702 patients with AD from first evaluation until they became too impaired to return to clinic. DSRS score increased an average of 4.48 points/y [95% confidence interval (CI): 4.14-4.82] throughout the entire range of severity. In contrast, the Mini Mental State declined an average of 2.15 points/y (95% CI: 1.85-2.46) during the first 2 years, accelerated to 3.83 points/y (95% CI: 3.28-4.38) during the subsequent 3 years, and then slowed to an annual decline of 1.63 points during the last 2 years (95% CI: 0.21-3.05). A younger age of symptom onset was associated with an increased rate of DSRS change (P=0.03). The DSRS provides a clinical measure of functional impairment in AD that increases about 4.48 points/y from the earliest symptomatic stage until patients become too severely impaired to return to clinic.