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Design Facts at a Glance

design_facts.jpgScope of Data | Samples | Instruments

Scope of Data

The Add Health study collects data to use in exploring the influences of both the individual attributes of respondents and the attributes of their various environments on health and health-related behavior. Below are examples of vital areas covered by the study:   

  • chronic and disabling conditions
  • injury
  • mental health status (focus on depression)
  • suicidal intentions/thoughts
  • health-service access and use
  • height
  • weight
  • blood pressure
  • biomarkers for metabolic, immune and inflammatory processes
  • medications
  • personality
  • religiosity and spirituality
  • sleep patterns
  • physical activity
  • diet
  • substance use/abuse
  • violence
  • delinquency, criminal offending, and involvement with the criminal justice system
  • education history and high school transcripts
  • work experiences and military service
  • relationships (parents, teachers, friends, romantic partners)
  • sexual behavior
  • sexually transmitted infections
  • contraception
  • pregnancy
  • children and parenting
  • household composition
  • neighborhood and school characteristics

Samples

Wave I, Stage 1

School sample: stratified, random sample of all high schools in the US. A school was eligible for the sample if it included an 11th grade and had a minimum enrollment of 30 students. A feeder school—a school that sent graduates to the high school and that included a 7th grade—was also recruited from the community.

High schools were stratified into 80 clusters

  • Region—Northeast, Midwest, South, West
  • Urbanicity—Urban, suburban, rural
  • School size—125 or fewer, 126–350, 351–775, 776 or more students
  • School type—public, private, parochial
  • Percent white—0, 1–66, 67–93, 94–100
  • Percent black—0, 1–6, 7–33, 34–100
  • Grade span—K–12, 7–12, 9–12, 10–12
  • Curriculum—general, vocational/technical, alternative, special education

Wave I, Stage 2

An in-home sample of 27,000 adolescents was drawn consisting of a core sample from each community plus selected special oversamples. Eligibility for oversamples was determined by an adolescent's responses on the In-School Questionnaire. Adolescents could qualify for more than one sample. In addition, parents were asked to complete a questionnaire about family and relationships.

Number of completed adolescent in-home interviews by sample

  • Core—12,105 adolescents representative of adolescents in grades 7–12 during the 1994–1995 school year in the US
  • Saturated schools—3,702 adolescents from 16 schools in which all students were selected for the in-home sample
  • Disabled—471 adolescents who reported having a limb disability
  • Blacks from well-educated families—1,038 black adolescents with a parent with a college degree
  • Chinese—334 adolescents
  • Cuban—450 adolescents
  • Puerto Rican—437 adolescents
  • Adolescents residing together Twin—1,981 adolescents
    Full sibling—1,186 adolescents
    Half sibling—783 adolescents
    Non-related adolescent—415 adolescents
    Sibling of twins—162 adolescents

Wave II

The Wave II in-home interview sample is the same as the Wave I in-home interview sample, with a few exceptions:

  • the majority of 12th-grade respondents were removed from the Wave II sample, as they exceeded the grade eligibility requirement (12th graders who were part of a genetic pair were retained);
  • the Wave I disabled sample was not reinterviewed at Wave II;
  • the Wave II sample contains a small number of adolescents who did not participate in the first wave; and
  • no parent interview was conducted at Wave II.

In addition, school administrators were contacted by telephone to update school information.  Information about neighborhoods/communities was gathered from a variety of previously published databases.

Wave III

The in-home Wave III sample consists of Wave I respondents who could be located and re-interviewed six years later. A sample of 1,507 partners of original respondents was also interviewed. Wave III also collected High School Transcript Release Forms as well as samples of urine (for sexually transmitted infections) and saliva (for HIV testing and, for full siblings and twins, DNA extraction).

Wave IV

All original Wave I in-home respondents were eligible for in-home interviews at Wave IV.  Wave IV also included collection of blood pressure readings, anthropometric measures (height, weight, and waist circumference), saliva for DNA, and blood spots from a fingerstick from all consenting respondents. To estimate the reliability of biological measures in the Add Health population, we repeated anthropometric measures and collection of biospecimens on 100 Wave IV respondents.

Instruments

Wave I

  • 90,118 adolescent In-School Questionnaires
    (September 1994–April 1995)
  • 164 School Administrator Questionnaires
    (September 1994–April 1995)
  • 20,745 adolescent In-Home Interviews
    (April 1995–December 1995)
  • Add Health Picture Vocabulary Test
    (April 1995–December 1995)
  • 17,669 Parent Questionnaires (parent specific component)
    17,713 Parent Questionnaires (child specific component)
    (April 1995–December 1995)

Wave II

  • 128 School Administrator Questionnaires
    (May 1996–June 1996)
  • 14,738 adolescent In-Home Interviews
    (April 1996–August 1996)

Wave III

  • 15,197 young adult In-Home Interviews and biomarker collection
    (July 2001–April 2002)
  • Add Health Picture Vocabulary Test Scores
    (July 2001–April 2002)

Wave IV

  • 15,701 adult In-Home Interviews and biomarker collection
    (April–June 2007 (pretest), January 2008–February 2009 (main study))