The validity of dependence as a health outcome measure in Alzheimer's disease.

Background: Relating to Alzheimer's disease (AD), dependence has been defined as the increased need for assistance due to deterioration in cognition, physical functioning, and behavior. Our objective was to evaluate the association between dependence and measures of functional impairment.
Methods: Data were compiled by the National Alzheimer's Coordinating Center. We used multinomial logistic regression to estimate the association between dependence and cognition, physical functioning, and behavior.
Results: The independent association with dependence was positive. Dependence was most strongly associated with physical functioning. A secondary analysis suggested a strong association of dependence with multiple impairments, as measured by the interaction terms, in more severe patients.
Conclusions: We find that dependence is simultaneously associated with physical functioning, cognition, and behavior, which support the construct validity of dependence. Dependence might be a more simple measure to explain the multifaceted disease progression of AD and convey the increasing need for care.