Neuropsychiatric Symptoms Predict Functional Status in Alzheimer's Disease

Background: Cognitive deficits are presumed to be the primary driver of functional impairment in Alzheimer's disease (AD); however, functional impairment is likely multifactorially determined. Objective: Our objective was to determine the relative contribution of neuropsychiatric symptoms in predicting ratings of functional status. Methods: A total of 223 patients received routine neurological and neuropsychological evaluations and met criteria of probable AD dementia based on the McKhann criteria. Demographic, cognitive, and neuropsychiatric variables were entered in a hierarchical linear regression analysis to predict functional status as measured by the Functional Activities Questionnaire (FAQ). Results: The total model explained 29.7% of the variance (p < 0.001) in FAQ. Importantly, neuropsychiatric variables explained 12.7% of the unique variance, with apathy and sleep as significant contributors. Conclusion: Two neuropsychiatric variables, apathy and changes in sleep/nighttime behaviors, predicted ratings of functional status in AD patients independent of age, global cognition, memory and executive function measures, and depressive symptoms. These results highlight the importance of neuropsychiatric symptoms in understanding and potentially treating the functional limitations so prevalent in AD.