title: Falling asleep: the determinants of sleep latency.
abstract: BACKGROUND
  Difficulty falling asleep (prolonged sleep latency) is a frequently reported problem in school-aged children.
  
  
  OBJECTIVE
  This study aimed to describe the distribution of sleep latency and factors that influence its duration.
  
  
  METHODS
  871 children of European mothers were recruited at birth. 591 (67.9%) children took part in the follow-up at 7 years of age. Sleep and daytime activity were measured objectively by an actigraph worn for 24 h.
  
  
  RESULTS
  Complete sleep data were available for 519 children (87.8%) with a mean age of 7.3 years (SD 0.2). Median sleep latency was 26 minutes (interquartile range 13-42). Higher mean daytime activity counts were associated with a decrease in sleep latency (-1.2 minutes per 102 movement count per minute, p = 0.05). Time spent in sedentary activity was associated with an increase in sleep latency (3.1 minutes per hour of sedentary activity, p = 0.01).
  
  
  CONCLUSIONS
  These findings emphasise the importance of physical activity for children, not only for fitness, cardiovascular health and weight control, but also for promoting good sleep.
authors.affiliation: Ritchie Centre for Baby Health Research, Monash Institute of Medical Research, Monash University, Melbourne, Australia.
authors.forename: G M
authors.initials: GM
authors.lastname: Nixon
authors.forename: J M D
authors.initials: JM
authors.lastname: Thompson
authors.forename: D Y
authors.initials: DY
authors.lastname: Han
authors.forename: D M O
authors.initials: DM
authors.lastname: Becroft
authors.forename: P M
authors.initials: PM
authors.lastname: Clark
authors.forename: E
authors.initials: E
authors.lastname: Robinson
authors.forename: K E
authors.initials: KE
authors.lastname: Waldie
authors.forename: C J
authors.initials: CJ
authors.lastname: Wild
authors.forename: P N
authors.initials: PN
authors.lastname: Black
authors.forename: E A
authors.initials: EA
authors.lastname: Mitchell
mesh_terms: D002648:Child; D015444:Exercise / Q000502:physiology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D017286:Polysomnography; D011446:Prospective Studies; D012044:Regression Analysis; D012621:Seasons; D007319:Sleep Initiation and Maintenance Disorders / Q000175:diagnosis / Q000209:etiology* / Q000523:psychology