The goal of this Notice of Special Interest (NOSI) is to encourage the use of existing cohorts and datasets for well-focused secondary analyses to investigate novel scientific ideas and/or address clinically related issues on: (1) aging changes influencing health across the lifespan (e.g., Alzheimer’s disease and Alzheimer’s disease-related dementias (AD/ADRD)), (2) diseases and disabilities in older persons, and/or (3) the changes in basic biology of aging that underlie these impacts on health (the hallmarks of aging). Activities of high priority include those addressing specific hypotheses in basic biological research, clinical aging research, behavioral or social research, and/or translational geroscience to inform: the design and implementation of future epidemiologic or human intervention studies; interventions in animal models of aging; research on behavioral and social factors over the life course that influence health (e.g., early life adversity); current geriatric practice in maintenance of health, disease management, and prevention of disability; or research testing of possible causal relationships between rates of aging and findings extracted by secondary analysis of the existing data. Existing datasets may also be used to develop and test new mathematical modeling and statistical analytical approaches. Analyses of sex and/or gender differences across health disparity groups (e.g., racial and ethnic groups, socioeconomic status, and sexual and gender minorities) are of high relevance. Use of cohorts that are linked to electronic health record systems and/or Centers for Medicare and Medicaid Services (CMS) administrative data are especially welcome.