title: The transition of sleep-wake patterns in early adolescence.
abstract: OBJECTIVE
  To examine the relationship between school grade level and sleep-phase preference in early adolescence.
  
  
  METHODS
  A school-based cross-sectional study using a Sleep Habit Questionnaire.
  
  
  METHODS
  NA.
  
  
  METHODS
  One thousand five hundred and seventy-two students, grade 4 to grade 8, from 3 junior high schools and 3 elementary schools in Taipei were recruited using multistage sampling method. The response rates were 98.4% (1547) for participants and 95.9% (1509) for their parents.
  
  
  METHODS
  NA.
  
  
  RESULTS
  Each student participant completed a Sleep Habit Questionnaire, including sleep schedules, the Morningness/Eveningness (M/E) scale, the Pubertal Developmental Scale, and the Sleepiness Scale. The morning (N = 367) and evening (N = 364) groups were operationally defined as participants with the top 25% and the bottom 25% of the M/E score, respectively. A mixed model was used in data analysis to address the cluster effects arising from the school-based study. We found that the M/E score decreased and the proportion of the evening type increased across grade 4 to grade 8. The evening type was associated with decreased nocturnal sleep and later bedtimes and rise times, as well as with increased daytime sleepiness and compensation for sleep on weekends.
  
  
  CONCLUSIONS
  Our findings support the hypothesis that school grade level is significantly associated with the transition to evening type in early adolescence. We report that environmental factors may play a more important role than biologic factors, such as age, sex, and pubertal development, in the transition from morning type to evening type at early adolescence. Future longitudinal study is necessary to determine the trajectories of sleep-wake patterns in adolescents and their predictors.
authors.affiliation: Department of Psychiatry, National Taiwan University Hospital, College of Medicine, National Taiwan University, Taipei, Taiwan, ROC. gaushufe@ccms.ntu.edu.tw
authors.forename: Shur-Fen
authors.initials: SF
authors.lastname: Gau
authors.forename: Wei-Tsuen
authors.initials: WT
authors.lastname: Soong
mesh_terms: D000293:Adolescent; D002648:Child; D003430:Cross-Sectional Studies; D006970:Disorders of Excessive Somnolence / Q000453:epidemiology; D005260:Female; D006184:Habits; D006801:Humans; D015994:Incidence; D008297:Male; D020178:Sleep Disorders, Circadian Rhythm / Q000453:epidemiology*; D011795:Surveys and Questionnaires