Cognitive deficits in preclinical Alzheimer's disease and vascular dementia: Patterns of findings from the Kungsholmen Project

Using data from the Kungsholmen Project (KP), we describe a program of research that focuses on preclinical cognitive markers of dementia. A large number of KP studies convincingly demonstrate that there is a preclinical period that spans several years in both Alzheimer's disease (AD) and vascular dementia (VaD), during which cognitive deficits are possible to detect. In AD, the preclinical impairment generalizes across a variety of cognitive domains, including episodic memory, executive functioning, perceptual speed, attention, verbal ability, and visuospatial skill. Although less research has been directed at cognition in preclinical VaD, the emerging evidence suggests a rather broad prodromal impairment in this disease as well. Thus, the nature of the cognitive impairment appears to be largely similar in preclinical AD and VaD. Despite the fact that average group differences in cognitive performance between incident dementia cases and controls are large several years before diagnosis, the distribution of scores in these groups overlap greatly. In order to improve group classification, future research should consider combining cognitive markers with preclinical indicators from other domains (e.g., biological, clinical, social, genetic) into multivariate prediction models.