title: Sleep duration and adiposity in older adolescents from Otago, New Zealand: relationships differ between boys and girls and are independent of food choice.
abstract: BACKGROUND
  While relationships between sleep and BMI have been extensively studied in younger children the effect of sleep duration on adiposity in adolescents, who are undergoing rapid growth periods, is less well known. There is also a lack of consistent evidence on the role of sleep on other measures of adolescent body composition which may be more reflective of health than BMI in this age group. Previous research investigating whether these relationships differ between sexes is also inconsistent. Therefore the objective of this study was to investigate relationships between sleep duration and multiple body composition measures in older adolescents and to investigate if these relationships differ between boys and girls.
  
  
  METHODS
  A web-based cross-sectional survey and anthropometric measurement of 685 adolescents (mean age 15.8 years) from 11 schools in Otago, New Zealand. Height and weight were measured by trained researchers and fat mass and fat-free mass were estimated using bio-impedance. Generalised estimating equations were used to examine associations between sleep duration and the following body composition measures: BMI, waist circumference (WC), waist-to-height ratio (WHtR), fat mass index (FMI), and fat-free mass index (FFMI). Analyses were adjusted for ethnicity, deprivation, the number of screens in the bedroom and fruit and vegetable consumption.
  
  
  RESULTS
  When data from all participants were analysed together, no significant relationships were seen between sleep duration and any body composition measure but significant sex interactions were seen. An hour increase in average nightly sleep duration in boys only was associated with decreases of 1.2% for WC, 0.9% for WHtR, 4.5% for FMI and 1.4% for FFMI in multivariate models. Similar results were seen for weekday and weekend night sleep duration.
  
  
  CONCLUSIONS
  Sex specific factors may play a role in relationships between sleep and body composition in older adolescents. The results in boys were most pronounced for FMI, a measure of total adiposity, which suggests that insufficient sleep in adolescent boys may affect fat mass more than lean mass and that the use of measures such as BMI may result in an under-estimation of relationships.
authors.affiliation: Department of Human Nutrition, University of Otago, PO Box 56, Dunedin 9054, New Zealand. paula.skidmore@otago.ac.nz.
authors.forename: Paula M L
authors.initials: PM
authors.lastname: Skidmore
authors.forename: Anna S
authors.initials: AS
authors.lastname: Howe
authors.forename: Maria A
authors.initials: MA
authors.lastname: Polak
authors.forename: Jyh Eiin
authors.initials: JE
authors.lastname: Wong
authors.forename: Alex
authors.initials: A
authors.lastname: Lubransky
authors.forename: Sheila M
authors.initials: SM
authors.lastname: Williams
authors.forename: Katherine E
authors.initials: KE
authors.lastname: Black
mesh_terms: D050154:Adiposity / Q000208:ethnology; D000293:Adolescent; D000294:Adolescent Behavior / Q000208:ethnology; D041923:Adolescent Development; D015992:Body Mass Index; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D004032:Diet / Q000009:adverse effects* / Q000208:ethnology; D005247:Feeding Behavior / Q000208:ethnology; D005260:Female; D006306:Health Surveys; D006801:Humans; D020407:Internet; D008297:Male; D009520:New Zealand / Q000453:epidemiology; D050177:Overweight / Q000453:epidemiology / Q000208:ethnology / Q000209:etiology* / Q000517:prevention & control; D015995:Prevalence; D012727:Sex Characteristics; D012890:Sleep; D012892:Sleep Deprivation / Q000208:ethnology / Q000503:physiopathology*; D018881:Suburban Health / Q000208:ethnology; D014504:Urban Health / Q000208:ethnology
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