title: Bedroom media, sedentary time and screen-time in children: a longitudinal analysis.
abstract: BACKGROUND
  Having electronic media in the bedroom is cross-sectionally associated with greater screen-time in children, but few longitudinal studies exist. The aim of this study was to describe longitudinal patterns of ownership and examine cross-sectional and longitudinal associations of bedroom media with children's sedentary behaviour.
  
  
  METHODS
  Data are from the Sport, Physical activity and Eating behaviour: Environmental Determinants in Young people (SPEEDY) study, collected at 3 time-points: baseline (2007, T0; age 10.3 ± 0.3 years), 1-year (T1y) and 4-year (T4y) follow-up. For each assessment, 1512 (44.9% male), 715 (41.0% male), and 319 (48.3% male) participants provided valid accelerometer data. Outcome variables were accelerometer-assessed sedentary time and self-reported screen-time. The presence of a television or computer in the bedroom was self-reported by participants and a combined bedroom media score calculated as the sum of such items. Cross-sectional and longitudinal associations between bedroom media and each outcome were examined using multi-level linear regression.
  
  
  RESULTS
  Bedroom TV ownership fell from 70.9% at T0 to 42.5% at T4y. Having a TV in the bedroom (beta; 95% CI*100, T0: -1.17; -1.88, -0.46. T1y: -1.68; -2.67, -0.70) and combined bedroom media (T0: -0.76; -1.26, -0.27. T1y: -0.79; -1.51, -0.07) were negatively associated with objectively measured weekly sedentary time at T0 and T1y. Having a computer in the bedroom (beta; 95% CI, T0: 0.15; 0.02, 0.29. T4y: 0.35; 0.10, 0.60) and combined bedroom media (T0: 0.09: 0.01, 0.18. T4y: 0.20; 0.05, 0.34) were positively associated with screen-time at T0 and T4y. Relative to participants without a computer throughout the study, children that had a computer in their bedroom at T0 but not at T4y (beta; 95% CI for change in screen-time: -8.02; -12.75, -3.29) reported smaller increases in screen-time.
  
  
  CONCLUSIONS
  The bedroom media environment changes with age and exhibits a complex relationship with children's sedentary behaviour. Modifying children's bedroom media environment may impact upon screen-time but appears unlikely to influence overall sedentary time.
authors.affiliation: UKCRC Centre for Diet and Activity Research (CEDAR), MRC Epidemiology Unit, University of Cambridge School of Clinical Medicine, Institute of Metabolic Science, Cambridge Biomedical Campus, Box 285, Cambridge CB2 0QQ, UK. aa595@medschl.cam.ac.uk.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Atkin
authors.forename: Kirsten
authors.initials: K
authors.lastname: Corder
authors.forename: Esther M F
authors.initials: EM
authors.lastname: van Sluijs
mesh_terms: D061725:Accelerometry; D000293:Adolescent; D002648:Child; D002652:Child Behavior; D002675:Child, Preschool; D003201:Computers; D003430:Cross-Sectional Studies; D004777:Environment; D005247:Feeding Behavior; D005260:Female; D006801:Humans; D016014:Linear Models; D008137:Longitudinal Studies; D008297:Male; D009043:Motor Activity; D055361:Multilevel Analysis; D010287:Parent-Child Relations; D012424:Rural Population; D057185:Sedentary Behavior; D057566:Self Report; D012959:Socioeconomic Factors; D013177:Sports; D013690:Television; D014505:Urban Population; D018910:Video Games