COGA participants). These criteria yielded a sample of 2,174 candidates from 1,528 nuclear families, of which 74% were single-participant families. Living participants’ contact details were in many cases determined through family members and internet searches. Death information was initially obtained from relatives, state death registries, newspapers, and online obituaries (e.g., obituaries.com, legacy.com, findgraves.com, Social Security Death Index). In addition, the National Death Index (NDI; https://www.cdc.gov/nchs/ndi/index.htm), a comprehensive database that compiles death certificate information from all states, was used to establish or validate dates and causes of death for deceased individuals and those of uncertain status.
