The purpose of this limited competition Request for Applications (RFA) is to continue data collection, development, and dissemination of the National Health and Aging Trends Study (NHATS) and National Study of Caregiving (NSOC). Continuation of the study requires both knowledge of, and access to, the NHATS and NSOC sample frames. Therefore, this RFA is limited to investigators and institutions with access to the NHATS and NSOC sample frame, as the frame will be used to contact and collect new data from participants. This RFA aims to provide additional research opportunities to use NHATS to formally study disability and Alzheimers disease (AD) and AD-related dementias (ADRD). This single integrated award combining NHATS and NSOC seeks to implement the comments of the NHATS Data Monitoring Committee to include continued the core elements of NHATS/NSOC and expand content to include enhanced cognitive/dementia measures, new sensory measures, richer dementia care measures, life course measures to capture sources of health disparities, improved residential care data, and an expanded accelerometry sample to facilitate AD/ADRD research that could enhance research targeting related NIA Dementia Care Milestones. Applicants are required to submit a Letter of Support from their institution confirming that they have access to personally identifiable information about NHATS and NSOC panel members and the ability to contact study participants for longitudinal follow-up and administrative/program data linkage.