title: Changes in bedtime schedules and behavioral difficulties in 7 year old children.
abstract: OBJECTIVE
  Causal links between disrupted sleep and behavioral problems in nonclinical populations are far from clear. Research questions were as follows: Are bedtime schedules associated with behavioral difficulties? Do effects of bedtime schedules on behavior build up over early childhood? Are changes in bedtime schedules linked to changes in behavior?
  
  
  METHODS
  Data from 10,230 7-year-olds from the UK Millennium Cohort Study, with bedtime data collected at 3, 5, and 7 years, and behavioral difficulties scores as rated by mothers and teachers were analyzed.
  
  
  RESULTS
  Children with nonregular bedtimes had more behavioral difficulties. There was an incremental worsening in behavioral scores as exposure through early childhood to not having regular bedtimes increased: mother rated (nonregular any 1 age, β = 0.53; nonregular any 2 ages, β = 1.04; nonregular all 3 ages, β = 2.10, P < .001) and teacher rated (β = 0.22, β = 0.73, β = 1.85, P < .001). Difference in differences analysis showed that for children who changed from nonregular to regular bedtimes there were clear nontrivial, statistically significant improvements in behavioral scores: A change between age 3 and 7 corresponded to a difference of β = -0.63, and a change between age 5 and 7 corresponded to a difference of β = -1.02). For children who changed from regular to nonregular bedtimes between ages 5 and 7 there was a statistically significant worsening in scores, β = 0.42.
  
  
  CONCLUSIONS
  Having regular bedtimes during early childhood is an important influence on children's behavior. There are clear opportunities for interventions aimed at supporting family routines that could have important impacts on health throughout life.
authors.affiliation: Department of Epidemiology and Public Health, University College London, 1-19 Torrington Place, London, WC1E 6BT, UK. y.kelly@ucl.ac.uk.
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Kelly
authors.forename: John
authors.initials: J
authors.lastname: Kelly
authors.forename: Amanda
authors.initials: A
authors.lastname: Sacker
mesh_terms: D002648:Child; D002652:Child Behavior / Q000502:physiology* / Q000523:psychology*; D002653:Child Behavior Disorders / Q000175:diagnosis / Q000453:epidemiology* / Q000523:psychology*; D002675:Child, Preschool; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D012890:Sleep / Q000502:physiology*; D012959:Socioeconomic Factors; D013997:Time Factors; D006113:United Kingdom / Q000453:epidemiology
keywords: International Centre for Lifecourse Studies in Society and Health; Millennium Cohort Study; child behavior; sleep