title: Patterns of adolescent physical activity, screen-based media use, and positive and negative health indicators in the U.S. and Canada.
abstract: OBJECTIVE
  To examine: (1) how adolescent physical activity (PA) and screen-based media use (SBM) relate to physical and social health indicators, and (2) crossnational differences in these relationships.
  
  
  METHODS
  Essentially identical questions and methodologies were used in the Health Behavior in School-Aged Children cross-sectional surveys of nationally representative samples of American (N = 14,818) and Canadian (N = 7266) students in grades 6 to 10. Items included questions about frequency of PA, SBM, positive health indicators (health status, self-image, quality of life, and quality of family and peer relationships), and negative health indicators (health complaints, physical aggression, smoking, drinking, and marijuana use).
  
  
  RESULTS
  In regression analyses controlling for age and gender, positive health indicators were uniformly positively related to PA while two negative health indicators were negatively related to PA. However, PA was positively related to physical aggression. The pattern for SBM was generally the opposite; SBM was negatively related to most positive health indices and positively related to several of the negative health indicators. The notable exception was that SBM was positively related to the quality of peer relationships. Although there were crossnational differences in the strength of some relationships, these patterns were essentially replicated in both countries.
  
  
  CONCLUSIONS
  Surveys of nationally representative samples of youth in two countries provide evidence of positive physical and social concomitants of PA and negative concomitants of SBM. These findings suggest potential positive consequences of increasing PA and decreasing SBM in adolescents and provide further justification for such efforts.
authors.affiliation: Prevention Research Branch, Division of Epidemiology, Statistics and Prevention Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Baltimore, Maryland, USA. iannottr@mail.nih.gov
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Iannotti
authors.forename: Michael D
authors.initials: MD
authors.lastname: Kogan
authors.forename: Ian
authors.initials: I
authors.lastname: Janssen
authors.forename: William F
authors.initials: WF
authors.lastname: Boyce
mesh_terms: D000293:Adolescent; D002170:Canada / Q000453:epidemiology; D002648:Child; D005260:Female; D015438:Health Behavior; D006304:Health Status; D006306:Health Surveys; D006801:Humans; D008019:Life Style; D008297:Male; D009043:Motor Activity; D012919:Social Behavior; D013690:Television; D014481:United States / Q000453:epidemiology; D018910:Video Games