PROJECT SUMMARY/ABSTRACT The National Social Life, Health, and Aging Project (NSHAP) is a nationally representative longitudinal study that focuses on the links between social, cognitive, mental, and physical health trajectories among older adults in the U.S. Beginning in 2005–06, with respondents ages 57 to 85, NSHAP has collected four rounds of data at 5-year intervals and included detailed information on: social well-being, including social relationships, social networks and social support; cognitive function, including Alzheimer’s disease and Alzheimer’s disease related dementias (AD/ADRD); mental health; physical performance; clinical diagnoses of cognitive and physical disease; biological samples; medications; sensory function; and accelerometer-measured daily activity and sleep. Additional data were collected during the COVID-19 pandemic on respondents’ health and experiences. The proposed NSHAP Round 5 (R5) will provide a fifth wave of data for Cohort 1 (born 1920-1947), a third wave for Cohort 2 (born 1948-1965), and a first wave for a newly recruited Cohort 3 (born 1966-1980). Together, the three cohorts will include adults aged 47 to 107. The experiences of people born after 1965 have differed dramatically from those born earlier and R5 will allow researchers to examine how the complex interplay of social and historical factors affects health trajectories as people age. In addition to the newly recruited Cohort 3, this study proposes to restructure the NSHAP sample to enhance the power of ethnoracial comparisons both in the new cohort and in the older cohorts by augmenting the greatly diminished surviving samples of Black and Hispanic respondents among Cohort 1 and Cohort 2 and recruiting equal numbers of Black, Hispanic, and White plus Other adults in Cohort 3. R5 will include repeat and new measures to permit cross-sectional and longitudinal analyses. Survey measures new to R5 will include questions about ethnoracial identity, discrimination over the lifespan, immigration experiences, language use, and social media use. We will also collect objective measures of health for cognition and AD/ADRD, sensory and physical functioning, wrist accelerometry, and anthropometrics. For the first time in NSHAP, we will include dominant grip strength, an objective online hearing test, leukocyte differentiation, Cystatin C for kidney function, and AD/ADRD plasma biomarkers. Data collected will permit examination of the social determinants of health disparities within and between ethnoracial groups, cohorts, and dyads. R5 will also provide the metrics to identify respondents with high mortality risk, which will enable us to prepare for a targeted, inter-round, follow-up study, to be proposed separately. R5 data will be archived and made publicly available at NACDA at the University of Michigan. NSHAP’s unparalleled combination of detailed social and biological measures make it uniquely suited to inform and support the work of medical practitio...