sábado, 12 de agosto de 2017

Schools Start Too Early | Features | CDC

Schools Start Too Early | Features | CDC

Centers for Disease Control and Prevention. CDC twenty four seven. Saving Lives, Protecting People

Schools Start Too Early

Boy sleeping in class

Starting school later can help adolescents get enough sleep and improve their health, academic performance, and quality of life.
Not getting enough sleep is common among high school students and is associated with several health risks including being overweight, drinking alcohol, smoking tobacco, and using drugs, as well as poor academic performance. One of the reasons adolescents do not get enough sleep is early school start times. The American Academy of Pediatrics has recommended that middle and high schools start at 8:30 a.m. or later to give students the opportunity to get the amount of sleep they need, but most American adolescents start school too early.
According to the 2014 School Health Policies and Practices Study,[1.88 MB] 93% of high schools and 83% of middle schools in the U.S. started before 8:30 a.m.
According to an earlier CDC study that analyzed US Department of Education data from the 2011-2012 school year:
  • 42 states reported that most (75%-100%) public middle and high schools started before 8:30 a.m.
  • The percentage of schools starting at 8:30 a.m. or later varied greatly by state. For example,
    • No schools in Hawaii, Mississippi, and Wyoming started after 8:30 a.m.
    • Most schools in North Dakota (78%) and Alaska (76%) started after 8:30 a.m.
Alert student raising hand
Adequate sleep enables improved academic performance.

Adolescents and Sleep

The American Academy of Sleep Medicine[221 KB] recommends that teenagers aged 13 to 18 years should regularly sleep 8 to 10 hours per day for good health. Adolescents who do not get enough sleep are more likely to
  • Be overweight.
  • Not engage in daily physical activity.
  • Suffer from symptoms of depression.
  • Engage in unhealthy risk behaviors such as drinking, smoking tobacco, and using illicit drugs.
  • Perform poorly in school.
During puberty, adolescents become sleepy later at night and need to sleep later in the morning as a result in shifts in biological rhythms.1 These biological changes are often combined with poor sleep habits (including irregular bedtimes and the presence of electronics in the bedroom).2 During the school week, school start times are the main reason students wake up when they do.3 The combination of late bedtimes and early school start times results in most adolescents not getting enough sleep.

Everyone Can Play an Important Role

  • Model and encourage habits that help promote good sleep:
    • Setting a regular bedtime and rise time, including on weekends, is recommended for everyone—children, adolescents, and adults alike. Adolescents with parent-set bedtimes usually get more sleep than those whose parents do not set bedtimes.
    • Dim lighting. Adolescents who are exposed to more light (such as room lighting or from electronics) in the evening are less likely to get enough sleep.
    • Implement a “media curfew.” Technology use (computers, video gaming, or mobile phones) may also contribute to late bedtimes. Parents should consider banning technology use after a certain time or removing these technologies from the bedroom.
  • Consider contacting local school officials about later school start times. Some commonly mentioned barriers to keep in mind are potential increases in transportation costs and scheduling difficulties.
Health care professionals
  • Educate adolescent patients and their parents about the importance of adequate sleep and factors that contribute to insufficient sleep among adolescents.
School officials
  • Learn more about the research connecting sleep and school start times. Good sleep hygiene in combination with later school times will enable adolescents to be healthier and better academic achievers.


  1. Crowley SJ, Acebo C, Carskadon MA. Sleep, circadian rhythms, and delayed phase in adolescence. Sleep Med. 2007;8:602–12.
  2. Bartel KA, Gradisar M, Williamson P. Protective and risk factors for adolescent sleep: a meta-analytic review. Sleep Med Rev. 2014;21:72–85.
  3. Knutson KL, Lauderdale DS. Sociodemographic and behavioral predictors of bed time and wake time among US adolescents aged 15 to 17 years. J Pediatr. 2009;154:426–30, 30 e1.

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