Research Using the NACC Database Strategies to reduce site differences in multisite studies: a case study of Alzheimer disease progression Lead Investigator: Art Noda Institution : Stanford E-Mail : email@example.com Proposal ID : 289 Proposal Description: The objectives of this study are to evaluate the magnitude and sources of site differences in a multisite study of rates of cognitive decline among patients with Alzheimer disease and to seek strategies to reduce the magnitude of site differences in this and future such studies. The MDS was employed. For each participant, the average rate of change in the Mini-Mental State Examination (MMSE) will be calculated. Participants who declined at least three MMSE points per year will be classified ???rapid decliners.??? Site differences in sociodemographic distributions and the percentage of rapid decliners will then be examined, and a signal detection approach will be used to identify the main correlates of rapid decline.