HRS investigates retirement and ageing and its influences on health outcomes in a population of adults in the United States of America. The study began in 1992, initially recruiting 12,652 individuals aged between 51 and 61 years, with oversampling of participants of ethnic minorities. The HRS has expanded over time to include multiple cohorts: the original HRS cohort (born from 1931 to 1941), Asset and Health Dynamics Among the Oldest Old (AHEAD; born from 1890 to 1923), Children of the Depression (CODA; born from 1924 to 1930), War Babies (born from 1942 to 1947), Early Baby Boomers (EBB; born from 1948 to 1953), Mid Baby Boomers (MBB; born from 1954 to 1959), and Late Baby Boomers (LBB; born from 1960 to 1965). Participants are community-dwelling individuals aged 50 years and older, with recruitment methods ensuring a representative sample of the United States population over 50 years. The study has continued to enrol new participants to maintain its representativeness, with the most recent additions being the Early Generation X (EGENX; born from 1966 to 1971) in 2022. Follow-up interviews are conducted every two years to track health, economic, and social changes over time.