title: Impact of a modest delay in school start time in Hong Kong school adolescents.
abstract: To examine the effects of a modest delay (15 min) in school start time (SST) on adolescent sleep patterns, mood, and behaviors.
  
  
  
  Two secondary schools in Hong Kong with a total of 1173 students (intervention: n = 617; comparison school n = 556) completed both baseline and follow-up questionnaires. School start time was delayed by 15 min, from 7:45 a.m. to 8:00 a.m., in the intervention school. The comparison school maintained their regular SST at 7:55 a.m. Students' sleep-wake patterns, daytime sleepiness, and mental and behavioral aspects were assessed by validated questionnaires before and after the intervention.
  
  
  
  Students in the intervention school significantly delayed their weekday wake-up time (p < 0.001) and increased their total time in bed (p < 0.001) when compared to students in the comparison school. Both groups experienced a delay in their weekday bedtime. The students in the intervention school showed improved mental health [General Health Questionnaire (GHQ) score, p = 0.015], better prosocial behaviors (p = 0.009), better peer relationships (p < 0.001), greater attentiveness (p < 0.001), less emotional problems (p = 0.002), and less behavioral difficulties (p < 0.001) as measured by Strengths and Difficulties Questionnaire (SDQ).
  
  
  
  A modest delay (15 min) in school start time can increase adolescent sleep with corresponding improvement in mood and behaviors. Current findings have significant implications for education policy, suggesting that school administrators and policy makers should systematically consider delaying school start time to promote sleep and health among school-aged adolescents.
  
  
  
  ChiCTR-TRC-12002798. The trial protocol can be accessed at: http://www.chictr.org/en/proj/show.aspx?proj=3955.
authors.affiliation: Department of Psychiatry, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, Hong Kong Special Administrative Region.
authors.forename: Ngan Yin
authors.initials: NY
authors.lastname: Chan
authors.affiliation: Department of Psychiatry, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, Hong Kong Special Administrative Region.
authors.forename: Jihui
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Department of Psychiatry, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, Hong Kong Special Administrative Region.
authors.forename: Mandy Wai Man
authors.initials: MW
authors.lastname: Yu
authors.affiliation: Department of Psychiatry, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, Hong Kong Special Administrative Region.
authors.forename: Siu Ping
authors.initials: SP
authors.lastname: Lam
authors.affiliation: Department of Psychology, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region.
authors.forename: Shirley Xin
authors.initials: SX
authors.lastname: Li
authors.affiliation: Department of Medicine and Therapeutics, Faculty of Medicine, The Chinese University of Hong, Shatin, Hong Kong Special Administrative Region.
authors.forename: Alice Pik Shan
authors.initials: AP
authors.lastname: Kong
authors.affiliation: Department of Pediatrics, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, Hong Kong Special Administrative Region.
authors.forename: Albert Martin
authors.initials: AM
authors.lastname: Li
authors.affiliation: Department of Psychiatry, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, Hong Kong Special Administrative Region. Electronic address: ykwing@cuhk.edu.hk.
authors.forename: Yun Kwok
authors.initials: YK
authors.lastname: Wing
mesh_terms: D000293:Adolescent; D000294:Adolescent Behavior / Q000523:psychology; D002940:Circadian Rhythm; D005260:Female; D006723:Hong Kong; D006801:Humans; D008297:Male; D012574:Schools; D012892:Sleep Deprivation / Q000517:prevention & control*; D013334:Students / Q000523:psychology; D011795:Surveys and Questionnaires; D013997:Time Factors
keywords: Adolescents; Comparison study; School start time; Sleep patterns