Rate of Cognitive Change Measured by Neuropsychologic Test Performance in 3 Distinct Dementia Syndromes

Abstract

Progressive decline in cognition is a hallmark feature of dementia, and the rate and profile of cognitive decline has been well characterized in Alzheimer disease (AD). Less is known about decline in cognition over time in other forms of dementia such as the behavioral variant of frontotemporal dementia (FTD) and primary progressive aphasia (PPA). The present study examined rate of cognitive decline across domains of memory, language, and executive function measured by neuropsychologic tests, in AD (n=84), FTD (n=66), and PPA (n=44). Patients were in the mild stages of dementia, with comparable duration of illness at the baseline evaluation. A best linear unbiased predictor (BLUP) analysis was used in which the slope of the relationship between a cognitive measure and time was estimated for each person. AD subjects demonstrated a floor effect on measures of memory at baseline and a decline on measures of language and executive functioning over time. FTD showed the greatest decline over time on the Mini-Mental State Examination, executive functioning, and naming. PPA patients demonstrated prominent decline on language measures, verbal memory measures, and attention. Results suggest that the profile of rate of change over time has unique features on the basis of the type of dementia syndrome. However, there is overlap in the profiles of decline likely influenced by the overlap in cognitive constructs measured by neuropsychologic tests. The comparison of the rate of decline in FTD and PPA may also reflect the neuroanatomic overlap in these syndromes over time.