title: Association of light exposure on physical activity and sedentary time in young people.
abstract: BACKGROUND
  To investigate whether light exposure was associated with objectively measured physical activity (PA) and sedentary behaviour in young people.
  
  
  METHODS
  Participants (n=229, 46.7% female) were young people (mean 8.8 years [SD±2.2]) from the borough of Camden, UK. Daily sedentary time, moderate and vigorous PA (MVPA) and light exposure were measured using a tri-axial accelerometer with an ambient light sensor during the summer. Multiple linear regression models examined associations between average daily light exposure, sedentary time and time in MVPA. Models were repeated investigating weekdays and weekend days separately. Analyses were adjusted for pre-specified covariables, including age, sex, device wear time, ethnic group, school and body fat.
  
  
  RESULTS
  There were significant associations between average daily light exposure and time sedentary (β coefficient=-11.2, 95% CI, -19.0 to -3.4) and in MVPA (β coefficient=3.5, 95% CI, 1.2 to 5.9). Light exposure was significantly associated with weekend sedentary time (β coefficient=-10.0, 95% CI, -17.6, -2.4), weekend MVPA (β coefficient=3.7, 95% CI, 1.7, 5.7), weekday sedentary time (β coefficient=-15.0, 95% CI, -22.7 to -7.2), but not weekday MVPA (β coefficient=2.0, 95% CI, -0.5 to 4.5).
  
  
  CONCLUSIONS
  Average daily light exposure is positively associated with time in MVPA and negatively associated with sedentary time. Increasing daylight exposure may be a useful intervention strategy for promoting physical activity.
authors.affiliation: Health Behaviour Research Centre, University College London, London WC1E6BT, UK. d.aggio@ucl.ac.uk.|Physical Activity Research Group, Department of Epidemiology and Public Health, University College London, London WC1E6BT, UK. d.aggio@ucl.ac.uk.
authors.forename: Daniel
authors.initials: D
authors.lastname: Aggio
authors.affiliation: Health Behaviour Research Centre, University College London, London WC1E6BT, UK. m.hamer@ucl.ac.uk.|Physical Activity Research Group, Department of Epidemiology and Public Health, University College London, London WC1E6BT, UK. m.hamer@ucl.ac.uk.
authors.forename: Lee
authors.initials: L
authors.lastname: Smith
authors.affiliation: Health Behaviour Research Centre, University College London, London WC1E6BT, UK. m.hamer@ucl.ac.uk.|Physical Activity Research Group, Department of Epidemiology and Public Health, University College London, London WC1E6BT, UK. m.hamer@ucl.ac.uk.
authors.forename: Abigail
authors.initials: A
authors.lastname: Fisher
authors.affiliation: Physical Activity Research Group, Department of Epidemiology and Public Health, University College London, London WC1E6BT, UK. m.hamer@ucl.ac.uk.
authors.forename: Mark
authors.initials: M
authors.lastname: Hamer
mesh_terms: D000273:Adipose Tissue; D000293:Adolescent; D000328:Adult; D003430:Cross-Sectional Studies; D005006:Ethnicity; D005260:Female; D006801:Humans; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D017440:Photoperiod; D012574:Schools; D057185:Sedentary Behavior