The ACT Data Repository is broadly defined as all data related to participants in the Adult Changes in Thought (ACT) Study. At a high level, data sources that make up the ACT Data Repository include data collected directly by the ACT Study — such as self-reported risk factor data, cognitive testing data, and research diagnoses produced by the ACT Study team in the course of working directly with participants — along with data from a number of other sources, as outlined below. Major categories of data that comprise the ACT Data Repository are included, along with a high-level description of each data domain.