title: Is spending time in screen-based sedentary behaviors associated with less physical activity: a cross national investigation.
abstract: BACKGROUND
  In Australia and the USA, national guidelines exist for limiting children's screen-exposure to two hours per day. This study aims to determine whether exceeding the suggested guidelines for screen-based sedentary behavior is associated with reduced levels of physical activity across different geographical regions.
  
  
  METHODS
  Data material were taken from the 2005/2006 survey of "Health Behaviour in School-aged Children (HBSC) study; A WHO cross-National Survey". Data were collected through questionnaires from 11-,13- and,15- year olds. The final sample included 200,615 adolescents from 39 different countries in Europe and North America. Gender and country stratified analyses regressed time spent in leisure-time vigorous physical activity (VPA) and days of 60 minutes moderate to vigorous physical activity (MVPA) on time spent in screen-based sedentary behaviors. To simplify interpretation, the estimates from each country were pooled using a meta-analytic procedure.
  
  
  RESULTS
  Exceeding 2 hrs of daily total screen-time was negatively associated with MVPA for both boys and girls, and with VPA for girls. When investigating the different types of screen-based behaviors separately, exceeding 2 hrs daily of TV viewing was associated with less MVPA for both boys and girls and less VPA for girls. Gaming was associated with less MVPA and VPA for boys, and non-gaming computer use was associated with higher levels of VPA for both genders. Stronger negative associations between physical activity and screen-based sedentary behaviors were found in countries where mean levels of physical activity were relatively high. The association between physical activity and sedentary behavior was not significantly associated with national levels of screen-based sedentary behaviors.
  
  
  CONCLUSIONS
  The displacement mechanism does not appear to be universal across countries. On a national level, negative associations between physical activity and screen-based sedentary behaviors are less likely to be found in countries with relatively low levels of physical activity. Consequently, national guidelines for limiting children and adolescents time in screen-based sedentary behavior may not be conducive to increasing levels of physical activity in all countries.
authors.affiliation: University of Bergen, Faculty of Psychology, Christiesgate 13, N-5015 Bergen, Norway. ole.melkevik@psyph.uib.no.
authors.forename: Ole
authors.initials: O
authors.lastname: Melkevik
authors.forename: Torbjørn
authors.initials: T
authors.lastname: Torsheim
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Iannotti
authors.forename: Bente
authors.initials: B
authors.lastname: Wold