The overarching goal of the Clinical Core (Core B) is to collect data in support of the Adult Changes in Thought (ACT) U19 Program Projects, Cores, and other studies using ACT data. The Clinical Core is responsible for participant communication and clinic and home visit data collection from ACT study participants, and coordinates with other Projects and Cores that include other data collection activities. One scientific challenge the Clinical Core must address is maintaining backwards compatibility while facilitating data collection using newer, modern methods and maintaining harmonization with companion studies. These considerations inform all aspects of the Clinical Core’s activities. The Clinical Core’s Specific Aims are: (1) Follow and retain current ACT participants. Refinements in the U19 Program include digital capture of extensive information on cognition beyond that previously collected using traditional approaches. The Clinical Core will continue data collection from home-based visits, an essential design characteristic for cohort retention. The Clinical Core will: (1a) expand, modernize, and improve established ACT data collection to follow cognition, physical function and function in daily life, interval changes in risk factors, health and social status and continue to identify incident cases of dementia and Alzheimer’s disease; and (1b) support proposed Projects and Cores and ACT related affiliated studies with targeted new data collection adding new processes to digitize and modernize cognitive tests. (2) Enroll, follow, and retain new ACT participants. The Clinical Core plans to increase enrollment to grow from 2,000 to 3,000 active dementia-free individuals. We will increase our geographic reach to include more sociodemographically and racially/ethnically diverse areas in the greater Puget Sound area and will oversample racial/ethnic minorities to achieve a goal of over 20% racial/ethnic minority enrollment. (3) Acquire and maintain antemortem autopsy approval and enhance communication with participants and their families to optimize postmortem intervals (PMI) for decedents who come to autopsy. The ACT study’s extensive infrastructure has led to >850 autopsies to date from the ACT cohort. The Clinical Core will work closely with the Neuropathology Core to use continuous quality improvement (CQI) approaches to maximize the proportion of consenting decedents who receive a rapid autopsy. (4) Coordinate with the Administrative and Data and Analysis Cores to ensure state-of-the-art quality control and data documentation of all data collected by the Clinical Core. The ACT Clinical Core builds on a quarter century of data collection from a population-based cohort of older adults and will expand, modernize and improve ACT data collection, provide outstanding support of Projects, Cores, and affiliated studies and those receiving ACT data through extensive data sharing infrastructure and have a larger and more sociodemographic and racially/...