title: Longitudinal associations of parental and peer influences with physical activity during adolescence: findings from the COMPASS study.
abstract: BACKGROUND
  To examine temporal variations in parental and peer influences on adolescent physical activity (PA) and whether these variations predicted changes in PA.
  
  
  METHODS
  We analyzed data from Years 1, 2 and 3 of the COMPASS study. Participants were 22 909 students in Grades 9 to 12 (mean age [years] = 15.42 ± 1.12, 46% boys, 85% White), who had completed the following survey items on 2 or more consecutive occasions: age, sex, grade, race/ethnicity, moderate-to-vigorous physical activity (MVPA), parental encouragement and parental instrumental support for PA, and number of active peers. We used a linear-mixed model to investigate longitudinal effects of parental and peer influences on changes in square-root transformed average MVPA. We used a generalized-estimating-equations (GEE) model to investigate compliance with Canadian PA guidelines for youth. These models included parental encouragement, instrumental support and number of active peers as time-varying predictors, adjusting for sociodemog raphic factors and grade as covariates, and accounting for the clustering within children and schools.
  
  
  RESULTS
  We found that adolescents perceived significantly less parental encouragement and instrumental support and reported fewer active peers as they got older. In addition, the adjusted models suggest that, for a one-unit increase in the score of parental encouragement, parental instrumental support and number of active peers, average MVPA significantly increased by 0.22 units, 0.23 units and 0.16 units, respectively. For the same one-unit increase, adjusted odds of an adolescent complying with the PA guidelines increased by 9%, 4% and 6%, respectively.
  
  
  CONCLUSIONS
  Promoting parental support and facilitating the formation and maintenance of a physically active friendship network may play an important role in attenuating declines in PA during adolescence.
authors.affiliation: School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: E Y
authors.initials: EY
authors.lastname: Lau
authors.affiliation: School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: G
authors.initials: G
authors.lastname: Faulkner
authors.affiliation: School of Public Health and Health Systems, University of Waterloo, Waterloo, Ontario, Canada.
authors.forename: W
authors.initials: W
authors.lastname: Qian
authors.affiliation: School of Public Health and Health Systems, University of Waterloo, Waterloo, Ontario, Canada.
authors.forename: S T
authors.initials: ST
authors.lastname: Leatherdale
mesh_terms: D000293:Adolescent; D000294:Adolescent Behavior; D002170:Canada; D015444:Exercise; D005260:Female; D017408:Guidelines as Topic; D006801:Humans; D016014:Linear Models; D008137:Longitudinal Studies; D008297:Male; D010287:Parent-Child Relations; D000067074:Peer Influence; D011446:Prospective Studies
keywords: active peers; parental encouragement; parental instrumental support; physical activity