title: Screen time, adiposity and cardiometabolic markers: mediation by physical activity, not snacking, among 11-year-old children.
abstract: BACKGROUND
  There is evidence for a relation of TV viewing with adiposity and increased cardiometabolic risk factors in children and adolescents. It is unclear to what extent this relation is mediated by snacking and lack of physical activity. We determined whether associations of screen time with adiposity and cardiometabolic markers were mediated by these behaviours.
  
  
  METHODS
  Children from a population-representative Dutch birth cohort (n=1447) reported screen time and other lifestyle factors by a questionnaire around the age of 11 years (range 10-14) and had anthropometry and cardiometabolic markers measured around the age of 12 years (range 12-14). Adjusted associations of screen time with snacking, physical activity, adiposity and cardiometabolic markers (total-to-high-density lipoprotein cholesterol (TC/HDLC) ratio, blood pressure, glycated haemoglobin) were assessed by using formal mediation analysis. We tested the hypothesized paths by structural equation modeling, which allows quantification of the indirect effects associated with potential mediators.
  
  
  RESULTS
  Children with ⩾20 h screen time per week consumed more snacks (1.9 vs 1.3 portions per day) and were less physically active (4.3 vs 4.8 days per week) than children with maximum 6 h screen time. Screen time was directly associated with higher adiposity (standardized β=0.10-0.12 depending on the outcome, P<0.001), and indirectly through less physical activity. The association of screen time with TC/HDLC ratio was almost completely mediated by adiposity (β=0.39, P<0.0001), and to a minor extent by physical activity (β=-0.06, P=0.02). There was no direct association of screen time with TC/HDLC ratio.
  
  
  CONCLUSIONS
  The adverse association of screen time with adiposity was partly mediated by physical activity, but not by snacking. The association of screen time with TC/HDLC ratio was almost completely mediated by adiposity. Our results may suggest that future efforts in society and public health should be directed to replace screen time with physical activity for reducing children's adiposity and cardiometabolic risk.
authors.affiliation: 1] Center for Nutrition, Prevention and Health Services, National Institute for Public Health and the Environment, Bilthoven, The Netherlands [2] Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: N E
authors.initials: NE
authors.lastname: Berentzen
authors.affiliation: Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: H A
authors.initials: HA
authors.lastname: Smit
authors.affiliation: Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: L
authors.initials: L
authors.lastname: van Rossem
authors.affiliation: Institute for Risk Assessment Sciences (IRAS), Division of Environmental Epidemiology, Utrecht University, Utrecht, The Netherlands.
authors.forename: U
authors.initials: U
authors.lastname: Gehring
authors.affiliation: Department of Epidemiology, University Medical Center Groningen, GRIAC Research Institute, University of Groningen, Groningen, The Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: Kerkhof
authors.affiliation: Department of Pulmonology, University Medical Center Groningen, GRIAC Research Institute, University of Groningen, Groningen, The Netherlands.
authors.forename: D S
authors.initials: DS
authors.lastname: Postma
authors.affiliation: 1] Center for Information Technology and Methodology Consultancy, National Institute for Public Health and the Environment, Bilthoven, The Netherlands [2] Division of Human Nutrition, Wageningen University, Wageningen, The Netherlands.
authors.forename: H C
authors.initials: HC
authors.lastname: Boshuizen
authors.affiliation: Center for Nutrition, Prevention and Health Services, National Institute for Public Health and the Environment, Bilthoven, The Netherlands.
authors.forename: A H
authors.initials: AH
authors.lastname: Wijga
mesh_terms: D050154:Adiposity; D015415:Biomarkers; D015992:Body Mass Index; D002318:Cardiovascular Diseases / Q000453:epidemiology / Q000517:prevention & control*; D002648:Child; D003201:Computers; D004522:Educational Status; D005247:Feeding Behavior / Q000523:psychology; D005260:Female; D007722:Health Knowledge, Attitudes, Practice; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008659:Metabolic Diseases / Q000453:epidemiology / Q000517:prevention & control*; D009426:Netherlands / Q000453:epidemiology; D012307:Risk Factors; D057185:Sedentary Behavior; D062410:Snacks; D013690:Television; D013997:Time Factors
chemical_list: D015415:Biomarkers