title: Evidence for a Possible Link between Bedtime and Change in Body Mass Index.
abstract: OBJECTIVE
  The aim of the current study was to examine the longitudinal relationship between bedtimes and body mass index (BMI) from adolescence to adulthood in a nationally representative sample.
  
  
  METHODS
  Three waves of data from the National Longitudinal Study of Adolescent Health were used to assess the bedtimes and BMI of 3,342 adolescents between 1994 and 2009. Hypotheses were tested with hierarchical linear models using a two-level, random intercept and slopes model.
  
  
  RESULTS
  Later average bedtime during the workweek, in hours, from adolescence to adulthood was associated with an increase in BMI over time (b = 0.035 kg/m(2) per min later bedtime per 6 years; standard error = 0.016; t = 2.12, degrees of freedom = 3,238, P < 0.05). These results remained significant after controlling for demographic characteristics and baseline BMI. Although sleep duration, screen time, and exercise frequency did not attenuate the relationship between workday bedtime and BMI over time, fast-food consumption was recognized as a significant partial mediator of the relationship between bedtimes and BMI longitudinally.
  
  
  CONCLUSIONS
  The results highlight bedtimes as a potential target for weight management during adolescence and during the transition to adulthood.
authors.affiliation: Department of Psychology, University of California, Berkeley, CA.
authors.forename: Lauren D
authors.initials: LD
authors.lastname: Asarnow
authors.affiliation: Department of Psychiatry, Division of Child and Adolescent Psychiatry, Columbia University, New York State Psychiatric Institute, New York, NY.
authors.forename: Eleanor
authors.initials: E
authors.lastname: McGlinchey
authors.affiliation: Department of Psychology, University of California, Berkeley, CA.
authors.forename: Allison G
authors.initials: AG
authors.lastname: Harvey
mesh_terms: D000293:Adolescent; D000294:Adolescent Behavior / Q000502:physiology; D000067697:Adolescent Health; D000328:Adult; D000375:Aging / Q000502:physiology; D015992:Body Mass Index; D003201:Computers / Q000706:statistics & numerical data; D004035:Diet Therapy; D015444:Exercise / Q000502:physiology; D057140:Fast Foods / Q000009:adverse effects; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D009765:Obesity; D012890:Sleep / Q000502:physiology*; D013690:Television / Q000706:statistics & numerical data; D013997:Time Factors; D055815:Young Adult
keywords: BMI; bedtime; longitudinal; obesity; sleep