Design of the Trial of Activity in Adolescent Girls (TAAG)

June Stevens, David M. Murray, Diane J. Catellier, Peter J Hannan, Leslie A. Lytele, John P. Elder, Deborah R. Young, Denise G. Simons-Morton, Larry S. Webber

Research output: Contribution to journalArticlepeer-review

132 Scopus citations

Abstract

The primary aim of the Trial of Activity in Adolescent Girls (TAAG) is to test an intervention to reduce by half the age-related decline in moderate to vigorous physical activity (MVPA) in middle school girls. The intervention will be evaluated using a group-randomized trial involving 36 middle schools. The primary endpoint is the mean difference in intensity-weighted minutes (i.e., MET-minutes) of MVPA between intervention and comparison schools assessed using accelerometry. The TAAG study design calls for two cross-sectional samples, one drawn from 6th graders at the beginning of the study and the second drawn from 8th graders at the end of the study following the 2-year implementation of the intervention. An important strength of this design over a cohort design is the consistency with the goals of TAAG, which focus on environmental-level rather than individual-level interventions to produce change. The study design specifies a recruitment rate of 80% and a smaller sample of girls at baseline (n=48 per school) than at follow-up (n=96 per school). A two-stage model will be used to test the primary hypothesis. In the first stage, MET-weighted minutes of MVPA will be regressed on school, time (baseline or follow-up), their interaction, ethnicity and week of data collection. The second stage analysis will be conducted on the 72 adjusted means from the first stage. In the main-effects model, we will regress the follow-up school mean MET-weighted minutes of MVPA on study condition, adjusting for the baseline school mean. The TAAG study addresses an important health behavior, and also advances the field of group-randomized trials through the use of a study design and analysis plan tailored to serve the main study hypothesis.

Original languageEnglish (US)
Pages (from-to)223-233
Number of pages11
JournalContemporary Clinical Trials
Volume26
Issue number2
DOIs
StatePublished - Apr 2005

Keywords

  • Accelerometry
  • Cross-sectional design
  • Group-randomized trial
  • Intervention
  • Middle School
  • Physical activity

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