There is an unmet need for effective, efficient, and economical methods for conducting AD prevention trials. Traditional in-person visits to clinical assessment sites are time consuming and costly and may exclude some people from participation, such as those who are older, or are less mobile or with significant medical illnesses. These may be the people who are at greatest risk for cognitive decline, and also may be without financial resources for services such as transportation to a study site. Prevention trials require long observation periods and these same issues of health, resources, and transportation may cause significant drop out. These obstacles increase expense of clinical trials which require large sample sizes, costly clinical staff and long observation periods. Thus, home-based assessments may lead to more representative recruitment of those most at risk for decline, as well as better retention and reduced study costs.