Factor structure of the National Alzheimer's Coordinating Centers uniform dataset neuropsychological battery: an evaluation of invariance between and within groups over time.

The neuropsychological battery from the National Alzheimer's Disease Coordinating Center is designed to provide a sensitive assessment of mild cognitive disorders for multicenter investigations. Comprising 8 common neuropsychological tests (12 measures), the battery assesses cognitive domains affected early in the course of Alzheimer disease. We examined the factor structure of the battery across levels of cognition [normal, mild cognitive impairment, dementia] based on Clinical Dementia Rating scores to determine cognitive domains tapped by the battery. Using data pooled from 29 Alzheimer's Disease Centers funded by National Institute on Aging, exploratory factor analysis was used to derive a general model using half of the sample; 4 factors representing memory, attention, executive function, and language were identified. Confirmatory factor analysis was used on the second half of the sample to evaluate invariance between groups and within groups over 1 year. Factorial invariance testing included systematic addition of constraints and comparisons of nested models. The general confirmatory factor analysis model had a good fit. As constraints were added, model fit deteriorated slightly. Comparisons within groups showed stability over 1 year. In a range of cognition from normal to dementia, factor structures and factor loadings will vary little. Further work is needed to determine whether domains become more or less distinct in severely cognitively compromised individuals.