title: Prospective associations between sedentary time, sleep duration and adiposity in adolescents.
abstract: OBJECTIVE
  The objective of this study was to investigate whether objectively measured sedentary time and sleep duration are associated with changes in adiposity from mid- to late adolescence.
  
  
  METHODS
  Students (n = 504, 42% boys) were recruited from schools in Cambridgeshire, UK. At baseline (mean age 15.0 ± 0.3 years), sedentary time was objectively measured by ≥3 days of combined heart rate and movement sensing. Concurrently, sleep duration was measured by combined sensing in conjunction with self-reported bed times. Fat mass index (FMI; kg/m(2)) was estimated at baseline and follow-up (17.5 ± 0.3 years) by anthropometry and bioelectrical impedance. FMI change (ΔFMI) was calculated by subtracting the baseline from follow-up values. Linear regression models adjusted for basic demographics, moderate-to-vigorous physical activity (MVPA), and depressive symptoms were used to investigate associations of sedentary time and sleep duration (mutually adjusted for one another) with ΔFMI.
  
  
  RESULTS
  FMI increased by 0.5 and 0.6 kg/m(2) in boys and girls, respectively, but there was no association between sedentary time and ΔFMI in either gender (p ≥ 0.087), and no association between sleep duration and ΔFMI in girls (p ≥ 0.61). In boys, each additional hour of baseline sleep significantly reduced the ΔFMI by 0.13 kg/m(2) (p = 0.049), but there was little evidence for this association after adjusting for MVPA and depressive symptoms (p = 0.15).
  
  
  CONCLUSIONS
  Sedentary time may not determine changes in adiposity from mid- to late adolescence, nor may sleep duration in girls. However, sleep length may be inversely associated with adiposity gain in boys, depending on whether the relationship is confounded or mediated by MVPA and depression.
authors.affiliation: MRC Epidemiology Unit, University of Cambridge School of Clinical Medicine, Cambridge, UK. Electronic address: paul.collings@mrc-epid.cam.ac.uk.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Collings
authors.affiliation: MRC Epidemiology Unit, University of Cambridge School of Clinical Medicine, Cambridge, UK.
authors.forename: Katrien
authors.initials: K
authors.lastname: Wijndaele
authors.affiliation: MRC Epidemiology Unit, University of Cambridge School of Clinical Medicine, Cambridge, UK.
authors.forename: Kirsten
authors.initials: K
authors.lastname: Corder
authors.affiliation: MRC Epidemiology Unit, University of Cambridge School of Clinical Medicine, Cambridge, UK.
authors.forename: Kate
authors.initials: K
authors.lastname: Westgate
authors.affiliation: MRC Epidemiology Unit, University of Cambridge School of Clinical Medicine, Cambridge, UK.
authors.forename: Charlotte L
authors.initials: CL
authors.lastname: Ridgway
authors.affiliation: MRC Epidemiology Unit, University of Cambridge School of Clinical Medicine, Cambridge, UK.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Sharp
authors.affiliation: UKCRC Centre for Diet and Activity Research (CEDAR), MRC Epidemiology Unit, University of Cambridge School of Clinical Medicine, Cambridge, UK.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Atkin
authors.affiliation: Developmental Lifecourse Research Group, Department of Psychiatry, University of Cambridge, Cambridge, UK.
authors.forename: Diane
authors.initials: D
authors.lastname: Bamber
authors.affiliation: Developmental Lifecourse Research Group, Department of Psychiatry, University of Cambridge, Cambridge, UK.
authors.forename: Ian
authors.initials: I
authors.lastname: Goodyer
authors.affiliation: MRC Epidemiology Unit, University of Cambridge School of Clinical Medicine, Cambridge, UK.
authors.forename: Soren
authors.initials: S
authors.lastname: Brage
authors.affiliation: MRC Epidemiology Unit, University of Cambridge School of Clinical Medicine, Cambridge, UK; Department of Sport Medicine, Norwegian School of Sports Science, Oslo, Norway.
authors.forename: Ulf
authors.initials: U
authors.lastname: Ekelund
mesh_terms: D000293:Adolescent; D015992:Body Mass Index; D015331:Cohort Studies; D004739:England; D005260:Female; D006801:Humans; D008297:Male; D009043:Motor Activity; D063766:Pediatric Obesity / Q000453:epidemiology / Q000209:etiology*; D011446:Prospective Studies; D012307:Risk Factors; D057185:Sedentary Behavior; D012737:Sex Factors; D012890:Sleep; D012892:Sleep Deprivation / Q000150:complications / Q000453:epidemiology; D013223:Statistics as Topic
keywords: Body fatness; Cohort study; Obesity; Sedentariness; Sleep length; Youth