Variability in cognitive presentation of Alzheimer's disease

The aim of the present study was to explore the nature and prevalence of phenotypic variations in Alzheimer's disease (AD). Neuropsychological profiles of a large cross-sectional cohort of patients with a clinical diagnosis of the disease were examined. All tests distinguished the AD group from controls confirming their sensitivity to the presence of early AD. Factor analysis of test scores revealed five factors, reflecting the discrete cognitive domains of memory, language, perceptuospatial abilities, executive skills, and praxis. Cluster analysis revealed distinct performance profiles that could not be accounted for by disease severity. Some patients showed an accentuation of memory impairment relative to other domains, whereas others showed relative sparing. Cognitive deficits other than memory were the salient presenting feature in a relatively high proportion of patients. A subset of the cohort (22%) showed grossly disproportionate impairments in one cognitive domain. The findings emphasise variability in presentation and indicate that distinct phenotypic variations appear to lie on a continuum rather than representing discrete forms of disease.