Donepezil for Alzheimer's Disease and Cognitive Decline

The goal of this clinical trial is to demonstrate potential improvements in clinical trial methods relating to dementia and cognitive decline. The main questions it aims to answer are: * Can an intervention's outcome be better assessed by a latent variable ("δ") integrating cognitive performance with functional status? * Can latent biomarkers of δ guide the selection of an intervention that will modulate dementia severity? * Can a latent variable, derived from information collected remotely from caregivers, preselect subjects most likely to respond to the intervention? * Is the effect of the intervention in fact medicated by changes in the targeted biomarker? In this case, the biomarker will be a latent variable derived from several proteins measured in blood (i.e., so-called "adipokines"). The intervention will be donepezil, a medication approved for the treatment of Alzheimer's Disease, but only recently associated with adipokine changes. Participants with cognitive impairment and their caregivers will be interviewed by telephone and those newly prescribed donepezil by their provider for cognitive impairment will be recruited and enrolled. On the basis of the caregiver's report, the cognitively impaired subjects will be assigned to two groups based on a prediction of their response to donepezil. Researchers will compare those groups to see if dementia severity, as measured by δ, improves in predicted responders, and whether the change in the d-score is mediated by changes in adipokines.