title: Determinants of change in children's sedentary time.
abstract: BACKGROUND
  Understanding the determinants of sedentary time during childhood contributes to the development of effective intervention programmes.
  
  
  OBJECTIVE
  To examine family and home-environmental determinants of 1-year change in objectively measured sedentary time after-school and at the weekend.
  
  
  METHODS
  Participants wore accelerometers at baseline and 1 year later. Longitudinal data for after-school and weekend analyses were available for 854 (41.5%male, mean ± SD age 10.2 ± 0.3 years) and 718 (41.8%male, age 10.2 ± 0.3 years) participants. Information on 26 candidate determinants, including socioeconomic status (SES), availability of electronic media and parental rules for sedentary behaviours was self-reported by children or their parents at baseline. Change in the proportion of registered time spent sedentary was used as the outcome variable in multi-level linear regression models, adjusted for age, sex, body mass index and baseline sedentary time. Simple and multiple models were run and interactions with sex explored.
  
  
  RESULTS
  Children from higher socioeconomic status families exhibited greater increases in after-school (beta; 95% CI for change in % time spent sedentary 1.02; 0.37, 1.66) and weekend (1.42; 0.65, 2.18) sedentary time. Smaller increases in after-school sedentary time were observed in children with more siblings (-1.00; -1.69, -0.30), greater availability of electronic media (-0.81; -1.29, -0.33) and, for boys, more frequent family visits to the park (-1.89; -3.28, -0.51) and family participation in sport (-1.28; -2.54, -0.02). Greater maternal weekend screen-time (0.45; 0.08, 0.83) and, in girls, greater parental restriction on playing outside (0.91; 0.08, 1.74) were associated with larger increases in weekend sedentary time. The analytical sample was younger, more likely to be female, had lower BMI and was of higher SES than the original baseline sample.
  
  
  CONCLUSIONS
  Intervention strategies aimed at reducing parents' weekend screen-time, increasing family participation in sports or recreation (boys) and promoting freedom to play outside (girls) may contribute towards preventing the age-related increase in sedentary time.
authors.affiliation: UKCRC Centre for Diet and Activity Research, Institute of Public Health, Cambridge, United Kingdom. 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: Ulf
authors.initials: U
authors.lastname: Ekelund
authors.forename: Katrien
authors.initials: K
authors.lastname: Wijndaele
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Griffin
authors.forename: Esther M F
authors.initials: EM
authors.lastname: van Sluijs
mesh_terms: D015992:Body Mass Index; D002648:Child; D002652:Child Behavior; D015444:Exercise; D005190:Family; D005260:Female; D015438:Health Behavior; D006801:Humans; D008297:Male; D010290:Parents; D010988:Play and Playthings; D057185:Sedentary Behavior; D012923:Social Class; D012931:Social Environment; D013177:Sports; D013690:Television