Project Summary This project, developed in response to RFA-AG-21-008, describes core plans for data collection and dissemination of the sixth wave (Wave VI) of the National Longitudinal Study of Adolescent to Adult Health (Add Health), when cohort members will be 39-48 years of age (mean 44). Add Health is a longitudinal study of a nationally representative sample of over 20,000 adolescents who were in grades 7-12 during the 1994-95 school year and have been followed for five waves to date. Over 25 years, Add Health has collected rich demographic, social, familial, socioeconomic, behavioral, psychosocial, cognitive, and health survey data from participants and their parents; a vast array of contextual data from participants' schools, neighborhoods, and geographies of residence; administrative data linked to participants, including birth and death certificates; and in-home physical and biological data from participants, including anthropometric measures, genetic markers, blood-based assays, and medications. Ancillary studies have added more information, including epigenetic, gene expression, and microbiome data. Thus, Add Health is exceptionally unique because it has a rich, multi- level, longitudinal array of data for a large nationally representative cohort of Americans who are entering midlife. Importantly, the overall health profile of the cohort as they make the transition to midlife is problematic across many dimensions. Moreover, health disparities by race, ethnicity, gender, socioeconomic status, sexual minority status, and rural-urban residence in this cohort are wide and, in some cases, widening. As such, rich longitudinal, multi-level, and nationally representative data are urgently needed to best understand the life course determinants of health trajectories and health disparities of US adults as they enter midlife. Wave VI of Add Health will fill this critical need. The overall goal of Wave VI of Add Health is to collect and disseminate the comprehensive data needed to best understand the social, economic, psychosocial, contextual, and biological determinants of health trajectories and disparities among this nationally representative cohort of Americans as they age into midlife. The project is focused around five aims: 1) Re-interviewing cohort members using predominantly web-based and in-person modes, with explicit attention to securing high response rates from racial/ethnic minority and low socioeconomic status participants; 2) Enriching study content in key domains that will elucidate mid- and later-life health trajectories and disparities; 3) Re-visiting cohort members who consent for an in-home health exam that includes venous blood collection and other important components of health; 4) Assaying biological specimens for important pre-disease and disease biomarkers; and 5) Cleaning, documenting, disseminating, archiving, promoting, and supporting Wave VI data for the scientific community. This project has extraordinary potential ...