title: Children's sedentary behaviour: descriptive epidemiology and associations with objectively-measured sedentary time.
abstract: BACKGROUND
  Little is known regarding the patterning and socio-demographic distribution of multiple sedentary behaviours in children. The aims of this study were to: 1) describe the leisure-time sedentary behaviour of 9-10 year old British children, and 2) establish associations with objectively-measured sedentary time.
  
  
  METHODS
  Cross-sectional analysis in the SPEEDY study (Sport, Physical activity and Eating behaviour: Environmental Determinants in Young people) (N=1513, 44.3% boys). Twelve leisure-time sedentary behaviours were assessed by questionnaire. Objectively-measured leisure-time sedentary time (Actigraph GT1M, <100 counts/minute) was assessed over 7 days. Differences by sex and socioeconomic status (SES) in self-reported sedentary behaviours were tested using Kruskal-Wallis tests. The association between objectively-measured sedentary time and the separate sedentary behaviours (continuous (minutes) and categorised into 'none' 'low' or 'high' participation) was assessed using multi-level linear regression.
  
  
  RESULTS
  Sex differences were observed for time spent in most sedentary behaviours (all p ≤ 0.02), except computer use. Girls spent more time in combined non-screen sedentary behaviour (median, interquartile range: girls: 770.0 minutes, 390.0-1230.0; boys: 725.0, 365.0 - 1182.5; p = 0.003), whereas boys spent more time in screen-based behaviours (girls: 540.0, 273.0 - 1050.0; boys: 885.0, 502.5 - 1665.0; p < 0.001). Time spent in five non-screen behaviours differed by SES, with higher values in those of higher SES (all p ≤ 0.001). Regression analyses with continuous exposures indicated that reading (β = 0.1, p < 0.001) and watching television (β = 0.04, p < 0.01) were positively associated with objectively-measured sedentary time, whilst playing board games (β = -0.12, p < 0.05) was negatively associated. Analysed in categorical form, sitting and talking (vs. none: 'low' β = 26.1,ns; 'high' 30.9, p < 0.05), playing video games (vs. none: 'low' β = 49.1, p < 0.01; 'high' 60.2, p < 0.01) and watching television (vs. lowest tertile: middle β = 22.2,ns; highest β = 31.9, p < 0.05) were positively associated with objectively-measured sedentary time whereas talking on the phone (vs. none: 'low' β = -38.5, p < 0.01; 'high' -60.2, p < 0.01) and using a computer/internet (vs. none: 'low' β = -30.7, p < 0.05; 'high' -4.2,ns) were negatively associated.
  
  
  CONCLUSIONS
  Boys and girls and children of different socioeconomic backgrounds engage in different leisure-time sedentary behaviours. Whilst a number of behaviours may be predictive of total sedentary time, collectively they explain little overall variance. Future studies should consider a wide range of sedentary behaviours and incorporate objective measures to quantify sedentary time where possible.
authors.forename: Tessa
authors.initials: T
authors.lastname: Klitsie
authors.forename: Kirsten
authors.initials: K
authors.lastname: Corder
authors.forename: Tommy L S
authors.initials: TL
authors.lastname: Visscher
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Atkin
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Jones
authors.affiliation: Medical Research Council, Epidemiology Unit, University of Cambridge, Cambridge, UK. esther.vansluijs@mrc-epid.cam.ac.uk.
authors.forename: Esther M F
authors.initials: EM
authors.lastname: van Sluijs
mesh_terms: D056044:Actigraphy; D002648:Child; D002652:Child Behavior / Q000523:psychology; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007899:Leisure Activities / Q000523:psychology; D008297:Male; D057185:Sedentary Behavior; D012737:Sex Factors; D012959:Socioeconomic Factors; D011795:Surveys and Questionnaires; D013997:Time Factors; D006113:United Kingdom / Q000453:epidemiology