Independence of changes in behavior from cognition and function in community-dwelling persons with Alzheimer's disease: a factor analytic approach.

The authors' main objective was to investigate the relationship between changes in psychopathological, cognitive and activity of daily living (ADL) instrument scores over 12 months in community-dwelling persons with Alzheimer's disease (AD). A secondary objective was to evaluate the validity of dividing the Clinical Dementia Rating (CDR), a global dementia staging instrument into cognitive and functional subscores. Changes in measures of psychopathology, cognition and function between the baseline and 12-month visits were entered into these post hoc analyses of data from a one-year clinical trial to evaluate behavioral, cognitive and functional assessment instruments for use in clinical trials with AD patients. Exploratory factor analysis was used to determine whether there was independence between changes in any of these three domains of interest for this disease population; participants were a cohort of 187 well-characterized, community-dwelling persons with AD. One-year change in the behavioral symptoms of this cohort of persons with AD was statistically independent from changes in scores on cognitive and functional measures. Some evidence of independence of 12 month changes in cognitive and functional measures was found. Cognitive and functional subscores for the CDR were supported. These findings suggest that changes in behavior and cognition in dementia may have distinct pathophysiologies.