title: Time for bed: associations with cognitive performance in 7-year-old children: a longitudinal population-based study.
abstract: BACKGROUND
  Little is known about the links between the time that young children go to bed and their cognitive development. In this paper we seek to examine whether bedtimes in early childhood are related to cognitive test scores in 7-year-olds.
  
  
  METHODS
  We examined data on bedtimes and cognitive test (z-scores) for reading, maths and spatial abilities for 11 178 7-year-old children from the UK Millennium Cohort Study.
  
  
  RESULTS
  At age 7, not having a regular bedtime was related to lower cognitive test scores in girls: reading (β: -0.22), maths (β: -0.26) and spatial (β: -0.15), but not for boys. Non-regular bedtimes at age 3 were independently associated, in girls and boys, with lower reading (β: -0.10, -0.20), maths (β: -0.16, -0.11) and spatial (β: -0.13, -0.16) scores. Cumulative relationships were apparent. Girls who never had regular bedtimes at ages 3, 5 and 7 had significantly lower reading (β: -0.36), maths (β: -0.51) and spatial (β: -0.40) scores, while for boys this was the case for those having non-regular bedtimes at any two ages (3, 5 or 7 years): reading (β: -0.28), maths (β: -0.22) and spatial (β: -0.26) scores. In boys having non-regular bedtimes at all three ages (3, 5 and 7 years) were non-significantly related to lower reading, maths and spatial scores.
  
  
  CONCLUSIONS
  The consistent nature of bedtimes during early childhood is related to cognitive performance. Given the importance of early child development, there may be knock on effects for health throughout life.
authors.affiliation: Department of Epidemiology and Public Health, University College London, , London, 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: D000367:Age Factors; D002648:Child; D002657:Child Development; D003071:Cognition / Q000502:physiology*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D015999:Multivariate Analysis; D011159:Population Surveillance; D012890:Sleep; D012959:Socioeconomic Factors; D006113:United Kingdom
keywords: Cognition; Epidemiology; Sleep