The data and specimen repository of the ADCC study will provide a unified mechanism for cataloging and storing data that can be efficiently shared across studies. This repository will also allow for important collaborations with other Alzheimer's Disease Centers across the US that are performing similar investigations of adults at increased risk of dementia. Data sharing across multiple institutions and investigators will be critical to optimize speed of acquisition and standardization of outcomes that may ultimately lead to the development of innovative tools for early detection and new treatment strategies. The repository will include cognitive data, human specimen samples (blood, cerebrospinal fluid), medical and family history information, and neuroimaging data. Data collected from participants enrolled in the ADCC will be stored indefinitely for future investigations.