Evidence Highlights

  • Following is an overview of the Minnesota Sleep Society Teen Sleep Loss Toolkit, highlighting some of the evidence:

    Why Start School at 8:30 am or later?

    Teenagers have a natural shift in their sleep clock, causing them to go to bed later. They sleep best between the hours 10:45 pm and 8 am. While homework, extracurricular activities and screen time contribute to this issue, the main modifiable factor is early school start times. (Carskadon, 2011)

    About two-thirds of the teenagers in the country report obtaining less than the recommended 8-10 hours of sleep. (Wheaton et al, 2016)


    Academic Performance

    Later start times decrease absences and tardiness and improve academic performance with evidence showing better scores in core courses and on standardized tests along with improved graduation rates. (Wahlstrom, 2014Edwards, 2012and McKeever & Clark 2017)


    Car Accidents

    Car crash rates decreased by 16.5% when school start time were moved one hour later. (Danner & Phillips, 2008)


    Risk-taking Behaviors like Substance Use

    A study involving 12,154 high school students found teenagers who obtain less than eight hours of sleep vs. more than eight hours of sleep were more likely to engage in risky behaviors such as fighting, smoking, alcohol/marijuana use and sexual activity. (McKnight-Eily, 2011)


    Depression and Suicidal Thoughts

    Teenagers sleeping less than eight hours at night were about 3 times more likely to make a suicide attempt compared to those sleeping nine hours or more. (Liu, 2004).



    Teenagers who were not obtaining adequate sleep at age 16 were 20% more likely to be obese by the age of 21. (Shakira, 2014)


    Sports Related Injury and Performance

    Teenage athletes reporting 6 hours of sleep per night are 4 times more likely to be injured than those getting 9 hours of sleep. (Milewski, 2014)


    High-Risk Students

    Students with multiple high-risk factors (low income, students of color) experienced increased negative consequences of sleep deprivation including increased substance use and serious mental health consequences.  Larger effects of later start times in respect to improved grades were seen at the lower end of the grade distribution  (Winsler et al 2014, Edwards, 2012)


    High-Achieving Students

    “Intelligence and an intense work ethic are no protection from the effects of sleep deprivation” as authors report high-achieving students who had their sleep restricted to five hours a night did worse on cognitive tasks compared to their well-rested peers. (Lo, 2015)

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