Add Health: Longitudinal Study of a Nationally Representative Sample of Adolescents in Grades 7-12 in the United States during the 1994-95 School Year, Followed into Adulthood with Five Interviews/Surveys in 1995, 1996, 2001-02, 2008, and 2016-18

The National Longitudinal Study of Adolescent to Adult Health [Add Health] is an ongoing longitudinal study of a nationally representative U.S. cohort of more than 20,000 adolescents in grades 7-12 (aged 12-19 years) in 1994 followed into adulthood with five interviews/surveys in 1995, 1996, 2001-02, 2008, and 2016-18. Add Health was designed to understand how social environments and behaviors in adolescence are linked to health and achievement outcomes in young adulthood. Add Health contains unprecedented environmental, behavioral, psychosocial, biological, and genetic data from early adolescence and into adulthood on a large, nationally representative cohort with unprecedented racial, ethnic, socioeconomic, and geographic diversity. Add Health has a large, multidisciplinary user base of over 50,000 researchers around the world who have published over 3,400 research articles. Add Health is housed at the Carolina Population Center of the University of North Carolina at Chapel Hill. Add Health datasets are distributed according to a tiered data disclosure plan designed to protect the data from the risk of direct and indirect disclosure of respondent identity. Add Health's large sample size, population diversity and rich longitudinal database of psychosocial, physical, and contextual data will permit investigation of an exceptionally broad range of phenotypes with known genetic variation. Prospective longitudinal measures are available to document change over time in each of these phenotypes, as well as change in the social environment and life experiences, making the Add Health sample ideal for understanding genetic linkages with health and behavior across the life course. The original design of Add Health included important features for understanding biological processes in health and developmental trajectories across the life course of young people, including an embedded genetic sample with more than 3,000 pairs of adolescents with varying biological resemblance (e.g., twins, full sibs, half sibs, and adolescents who grew up in the same household but have no biological relationship), testing of saliva and urine for sexually transmitted infections and HIV, and biomarkers of cardiovascular health, metabolic processes, immune function, renal function, and inflammation. Add Health therefore has critical objective indicators of health status and disease markers in young adulthood, well before chronic illness or its complications emerge in later adulthood. Because DNA has been collected on the full sample at Wave IV, it is possible to link genetic profiles with social, behavioral, and biological measures over time from adolescence into adulthood. Add Health sampled the multiple environments in which young people live their lives, including the family, peers, school, neighborhood, community, and relationship dyads, and provides independent and direct measurement of these environments over time. Add Health contains extensive longitudinal information on health-related behavior, including life histories of physical activity, involvement in risk behavior, substance use, sexual behavior, civic engagement, education, and multiple indicators of health status based on self-report (e.g., general health, chronic illness), direct measurement (e.g., overweight status and obesity), and biomarkers. No other data resource with this expanse of genotype and phenotype data on a large nationally representative longitudinal sample with race, ethnic, socioeconomic, and geographic diversity exists. A complete reference guide on study design and accomplishments can be found on the Add Health website: https://cdr.lib.unc.edu/concern/articles/6t053j27s.]]>
Quality Control Analysis of Add Health GWAS DataQuality Control of Gene Expression DataThe Wave IV DNA collection was intended to address specific study aims of the Add Health Program Project but also to serve as an archive for future genetic testing when new technology developments could be exploited and genotyping costs reduced. Among eligible respondents at Wave IV, 92% were located and 80% re-interviewed, yielding a Wave IV sample size of 15,701. Of the 15,701 respondents interviewed, 96% consented to DNA collection for purposes of the Program Project aims, and 12,234 (78%) agreed to archive their DNA for future analysis "related to long term health". The extracted DNA is of high quality. The table below displays information (unweighted) about consent for DNA collection and archiving by race/ethnicity. Although there is some variation, primarily regarding archiving of samples, consent was uniformly high across groups, and yielded more than 12,000 samples for genome-wide genotyping with 9,974 passing quality control review. Race/ Ethnicity Group Number (percentage) consenting to collect DNA Number (percentage) of consenting respondents who consent to archive Number (percentage) of consenting archive respondents who pass QC for dbGaP file Hispanic 2393 (96%) 1883 (75%) 1448 (77%) Black 3312 (96%) 2491 (72%) 2081 (84%) White 8372 (97%) 7088 (82%) 5896 (83%) Other, non-Hispanic (Asian, American-Indian, other, including missing race) 1063 (95%) 772 (69%) 550 (71%) TOTAL 15,140 (96%) 12,234 (78%) 9974 (82%) The Wave IV sample consists of Wave I participants who agreed to participate in the study at Wave IV. The information below provides background on the Wave I sampling design, Wave I in-home sample that is followed prospectively through time, and the longitudinal design. In-Home Wave I Samples: Main (core) sample All students who completed the In-School Questionnaire plus those who did not complete a questionnaire but were listed on a school roster were eligible for selection into the core in-home sample. This is a nationally representative sample of adolescents in grades 7 through 12 in the US in the 1994-95 school year. Students in each school were stratified by grade and sex. About 17 students were randomly chosen from each stratum so that a total of approximately 200 adolescents were selected from each of the 80 pairs of schools. A total core sample of 12,105 adolescents was interviewed. Special oversamples Ethnic: Based on self-reported data from the In-School Questionnaire, four supplementary ethnic-group samples were drawn. Following are the numbers of completed cases in these samples: 1,038 blacks from well-educated families (with a parent with a college degree) 334 Chinese 450 Cuban 437 Puerto Rican In addition, the in-home Wave I sample contains more than 1,500 Mexican-Americans and significant numbers of Nicaraguans, Japanese, South Koreans, Filipinos, and Vietnamese. Saturation: To enable analysis of social networks, all enrolled students in 16 schools were selected for in-home interviews. These were two large schools (with a total combined enrollment exceeding 3,100) and 14 small schools (with enrollments of fewer than 300). One of the large schools is predominantly white and is located in a mid-sized town. The other is ethnically heterogeneous and is located in a major metropolitan area. The 14 small schools, some public and some private, are located in both rural and urban areas. Disabled: A sample of 589 students self-reported on the In-School Questionnaire that they had physical disabilities involving the use of their limbs. Adolescents were considered to be limb disabled if they indicated on the In-School Questionnaire (1) that they had difficulty using their hands, arms, legs, or feet because of a physical condition and (2) that they had used a mechanical device (e.g., wheelchair, cane, brace, or artificial limb) for the past 12 months or more. Genetic: The genetic sample consists of pairs of siblings living in the same households. Identical twins, fraternal twins, and half siblings were sampled with certainty. In addition, non-related pairs, such as step-siblings, foster children, and adopted (non-related) siblings, were part of the genetic sample. The majority of full-sibling pairs entered into the sample by chance (disproportionately drawn from the 16 saturation-school samples). Longitudinal Design Beginning with an in-school questionnaire administered to a nationally representative sample of students in grades 7-12, the study followed up with a series of in-home interviews conducted in 1995, 1996, 2001-02, and 2008. The fifth wave of data collection was conducted in 2016-2018. Other sources of data include questionnaires for parents, siblings, fellow students, and school administrators and interviews with romantic partners. Preexisting databases provide information about neighborhoods and communities. The following figure shows the longitudinal design of Add Health including the recent Wave V interview. ]]>
Initiated in 1994 and supported by three program project grants to date from the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) with co-funding from 23 other federal agencies and foundations, Add Health is the largest, most comprehensive longitudinal survey of adolescents ever undertaken. Add Health was developed in response to a mandate from the U.S. Congress to fund a study of adolescent health, and Waves I and II focus on the forces that influence adolescents' health and risk behaviors, including personal traits, families, friendships, romantic relationships, peer groups, schools, neighborhoods, and communities. As participants aged into adulthood, the scientific goals of the study expanded. Wave III, conducted when respondents were between 18 and 26 years old, focuses on how adolescent experiences and behaviors are related to decisions, behavior, and health outcomes in the transition to adulthood. At Wave IV, respondents were ages 24-32 and beginning to assume adult roles and responsibilities. Wave IV significantly expanded biological data collection with markers of cardiovascular, metabolic, and immune function. Follow up at Wave IV has enabled researchers to study developmental and health trajectories across the life course of adolescence into adulthood using an integrative approach that combines the social, behavioral, and biomedical sciences in its research objectives, design, data collection, and analysis. The multilevel and longitudinal nature of the environmental data of the Add Health study allows researchers to characterize the social, physical and health environment in ways that are not possible with other studies. This design feature provides unique scientific opportunities to study the roles of gene-environment interactions (GxE) and gene environment correlations (rGE) in understanding health and behavioral outcomes. Add Health has promoted the research opportunities and use of its data within the broad social and biomedical communities, resulting in prolific research production with unparalleled disciplinary breadth. Add Health has become a national and global data resource for over 50,000 Add Health researchers, who have obtained more than 1000 independently funded research grants and produced over 3,400 research articles published in 750+ different disciplinary journals. Add Health data provide a broad disciplinary base for research and methodological training; more than 800 masters' theses and doctoral dissertations are based on Add Health. The Add Health website (https://addhealth.cpc.unc.edu/) averages over 60,000 hits per month. ]]>