title: Perceived family functioning and friendship quality: cross-sectional associations with physical activity and sedentary behaviours.
abstract: BACKGROUND
  This study examined the association of adolescent-reported family functioning and friendship quality with objectively-measured moderate to vigorous physical activity (MVPA), sedentary time, and self-reported sedentary behaviours.
  
  
  METHODS
  Data are from the ROOTS study. MVPA and sedentary time were assessed using combined movement and heart rate sensing. Time spent TV viewing, using the internet, playing video games, doing homework and reading for pleasure was self-reported. Data on objectively-measured and self-reported outcomes for weekdays was available for 738 (age 14.5y, 55.7% female) and 800 (56.3% female) participants, respectively. Adolescents perceived family functioning and friendship quality (Two subscales: 'Good friendship qualities', 'Friendship difficulties') was assessed by questionnaire. Analyses were conducted using multi-level linear or logistic regression.
  
  
  RESULTS
  Adolescents reporting better family functioning accumulated more MVPA on weekdays (beta; 95% confidence interval: 0.57; 0.17,0.98). Higher scores on the good friendship qualities subscale was associated with greater MVPA throughout the week (weekdays: 1.13; 0.62,1.65, weekend: 0.56; 0.09,1.02) and lower sedentary time on weekdays (-10.34; -17.03,-3.66). Boys from better functioning families were less likely to report playing video games at the weekend (OR; 95% confidence interval: 0.73; 0.57,0.93) or reading for pleasure (weekday: 0.73; 0.56,0.96 weekend: 0.75; 0.58,0.96). Boys who attained higher scores on the good friendship qualities scale were less likely to play video games at the weekend (0.61; 0.44,0.86) or report high homework on weekdays (0.54; 0.31,0.94). A higher score for good friendship qualities was associated with lower odds of girls playing video games during the week (0.76; 0.58,1.00) or reading for pleasure at the weekend (0.61; 0.42,0.88). Girls that reported fewer friendship difficulties had lower odds of high TV viewing (0.76; 0.62,0.93) or playing video games (0.71; 0.52,0.97) at the weekend, and lower odds of reading for pleasure (0.63; 0.49,0.81) or reporting high homework on weekdays (0.70; 0.52,0.95).
  
  
  CONCLUSIONS
  Family functioning and friendship quality exhibit a complex pattern of association with physical activity and sedentary behaviour that varies by sex and day of the week. Findings highlight the potential value of targeting interpersonal aspects of the family and friendships as an adjunct to behaviour change interventions.
authors.affiliation: MRC Epidemiology Unit & UKCRC Centre for Diet and Activity Research (CEDAR), University of Cambridge School of Clinical Medicine, 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.affiliation: MRC Epidemiology Unit & UKCRC Centre for Diet and Activity Research (CEDAR), University of Cambridge School of Clinical Medicine, Cambridge Biomedical Campus, Box 285, Cambridge, CB2 0QQ, UK. klc29@medschl.cam.ac.uk.
authors.forename: Kirsten
authors.initials: K
authors.lastname: Corder
authors.affiliation: Developmental Psychiatry Section, Department of Psychiatry, University of Cambridge, Cambridge, UK. ig104@cam.ac.uk.
authors.forename: Ian
authors.initials: I
authors.lastname: Goodyer
authors.affiliation: Developmental Psychiatry Section, Department of Psychiatry, University of Cambridge, Cambridge, UK. drdianebamber@gmail.com.
authors.forename: Diane
authors.initials: D
authors.lastname: Bamber
authors.affiliation: MRC Epidemiology Unit & UKCRC Centre for Diet and Activity Research (CEDAR), University of Cambridge School of Clinical Medicine, Cambridge Biomedical Campus, Box 285, Cambridge, CB2 0QQ, UK. ulf.ekelund@nih.no.|Department of Sport Medicine, Norwegian School of Sports Sciences, Oslo, Norway. ulf.ekelund@nih.no.
authors.forename: Ulf
authors.initials: U
authors.lastname: Ekelund
authors.affiliation: MRC Epidemiology Unit & UKCRC Centre for Diet and Activity Research (CEDAR), University of Cambridge School of Clinical Medicine, Cambridge Biomedical Campus, Box 285, Cambridge, CB2 0QQ, UK. Soren.Brage@mrc-epid.cam.ac.uk.
authors.forename: Soren
authors.initials: S
authors.lastname: Brage
authors.affiliation: Developmental Psychiatry Section, Department of Psychiatry, University of Cambridge, Cambridge, UK. vjd20@medschl.cam.ac.uk.
authors.forename: Valerie
authors.initials: V
authors.lastname: Dunn
authors.affiliation: MRC Epidemiology Unit & UKCRC Centre for Diet and Activity Research (CEDAR), University of Cambridge School of Clinical Medicine, Cambridge Biomedical Campus, Box 285, Cambridge, CB2 0QQ, UK. esther.vansluijs@mrc-epid.cam.ac.uk.
authors.forename: Esther M F
authors.initials: EM
authors.lastname: van Sluijs
mesh_terms: D000293:Adolescent; D000294:Adolescent Behavior; D003430:Cross-Sectional Studies; D015444:Exercise; D005190:Family; D005260:Female; D033062:Friends; D015438:Health Behavior; D006801:Humans; D020407:Internet; D016015:Logistic Models; D008297:Male; D016017:Odds Ratio; D010465:Perception; D057185:Sedentary Behavior; D057566:Self Report; D012737:Sex Factors; D011795:Surveys and Questionnaires; D013690:Television; D018910:Video Games