Rate of decline in Alzheimer disease measured by a Dementia Severity Rating Scale.

OBJECTIVE: To measure clinically relevant change in Alzheimer disease (AD) using a family member-completed Dementia Severity Rating Scale (DSRS) questionnaire.
BACKGROUND: Measuring rate of change provides important clinical information. Most neuropsychologic scores change nonlinearly, complicating their use as a predictor of change throughout the illness.
METHODS: 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.
RESULTS: 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).
CONCLUSIONS: 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.