The importance of sleep

Written by: John Dabell | Published:
Image: Adobe Stock

All teachers know that tired students make for poor learners. John Dabell looks at what the research tells us about why sleep is a fundamental part of the thinking and learning process

Without a good night’s sleep, our alertness, cognitive function, psycho-motor coordination and mood all go out the window. Our concentration and memory are noticeably affected and we get grumpy. Indeed, a lack of sleep is major risk factor for mistakes and poor decision-making.

Tiredness directly affects our productivity, emotional balance, brain and heart health, immune system, creativity, vitality, and even our weight. It compromises our cardiovascular health, energy balance, and ability to fight infections. There is also a higher risk of obesity, diabetes, injuries, poor mental health, and problems with attention and behaviour.

Indeed, neuroscientist Matthew Walker in Why We Sleep (2017) and clinical psychologist Vicki Culpin in The Business of Sleep (2018) warn that regularly sleeping less than seven hours a night is a disaster for our mental and physical wellbeing.

Eight hours a night is often quoted as being the magic figure, but the optimum sleeping time varies across ages and is affected by several factors, including lifestyle and health.

Although everyone differs in their vulnerability to sleep deprivation, performance is impaired when someone achieves two hours less sleep than required and performance deteriorates progressively with an accumulating sleep debt...

Sleep and teens: The research

Current sleep recommendations are founded on solid science and decades of observation and research. According to the National Sleep Foundation in America, teens aged 13 to 18 need about eight to 10 hours of sleep each night, although very few actually achieve that amount (Eaton et al, 2010) and many are chronically sleep deprived.

Dr Mary A Carskadon, a prominent American researcher in sleep and an authority on adolescent sleep, said: “Fundamentally, the issue is they are not filling up their tank at night and so they are starting the day with an empty tank.” (Carskadon, 2011; see also her Frontline interview)

Poor sleep in teenagers is also linked with risky behaviours including smoking, drinking, stimulant abuse, fighting, physical inactivity, anxiety, and suicidal tendencies.

Dr Carskadon points to a number of studies that have shown associations between insufficient sleep and adverse health outcomes in teens, including increased obesity risk, higher rates of motor vehicle accidents and accidental injuries, reduced cardiovascular health, and increased risk of depression.

However, the reasons why teenagers are not getting enough sleep are complex and varied, including extra-curricular activities, after-school jobs, home care responsibilities, homework, and the use and abuse of technology, including social media.

Good sleep management and sleep hygiene (behavioural and environmental practice that promotes better quality sleep) does play its part, but it is not just about going to bed earlier – this is about the science of sleep and the biology of teens.

Researchers have found that the sleep patterns of younger children allow them to get up early and be ready for learning. However, the biology of adolescents is at odds with early mornings. The research has found that the secretion of the sleep hormone melatonin begins at around 10:45pm and continues until about 8am, making it hard to get to sleep before 11pm and to wake up early.

The Teensleep Project, run by the Nuffield Department of Clinical Neurosciences at the University of Oxford, is the biggest study ever to look at teenage circadian delay and the effects of sleep education on academic, health and sleep outcomes. It states: “In adolescence, biological rhythms change in such a way that makes it difficult for teenagers to go to sleep and get up early. Therefore, asking an adolescent to get up at 7am to start school at 9am is akin to asking a 55-year-old to get up at 5am: this leads to a significant amount of sleep deprivation.

“This sleep deprivation interacts with biological rhythms, creating a period of low energy and tiredness which lasts into mid-morning.”

Walker and van der Helm (2009) found in their research that getting enough sleep allowed students to create new memory associations more effectively, whereas a lack of sleep hindered their ability and made them more likely to forget positive memories and to remember negative ones.

Dr Judith Owens is director of Harvard Medical School’s Center for Pediatric Sleep Disorders and says that the scientific literature shows that children and adolescents experience better learning and academic success and greater physical and mental health when their sleep is protected (Owens, 2014).

In a 2013 interview, she explained: “If teens’ sleep patterns are in conflict with their natural circadian rhythms, then that also has repercussions on cognitive function and emotional regulation as well as potential health consequences.” (Jegtvig, 2013)

An early start to the school day is therefore detrimental to health and learning. Dr Owens added: “The research is clear that adolescents who get enough sleep have a reduced risk of being overweight or suffering depression, are less likely to be involved in automobile accidents, and have better grades, higher standardised test scores and an overall better quality of life.” (Owens, 2014)

About time

According to a survey by Dunster et al (2018), the closer students get to a full eight hours a night of sleep, the better their grades, so one strategy proposed is to delay secondary school start times in order to lengthen adolescent sleep.

In 2014, the American Academy of Paediatrics issued a policy statement stating that “high schools and middle schools should start no earlier than 8:30am because there was compelling scientific evidence that early start times put students under physical and psychological stress correlated to emotional problems, obesity, sports injuries and other health risks”.

In their research, Kelley et al (2014) say that synchronising education start times to adolescent biology is the obvious way to address the problem of chronic sleep deprivation currently experienced by adolescents on school days. The authors conclude that students’ start times should be 8:30am or later at age 10; 10am or later at 16; and 11am or later at 18, and that synchronising education start times would enable immediate advances in attainment.

The Teensleep Project, meanwhile, argues that by changing the school start time by one hour, from 9am to 10am, teenagers will simply be more awake, alert and ready to learn.
Despite the evidence, starting later in the day would cause problems, especially for working parents. In response to a petition calling for schools to start at 10am the Department for Education said: “The government has given all schools the ability to set their own school hours so all schools have the autonomy to make decisions about the timetable and duration of their school day, including the flexibility to decide when their school day should start and finish.” (BBC, 2019)

  • John Dabell is a teacher, teacher trainer and writer. He has been teaching for 25 years and is the author of 10 books. Visit and read his previous best practice articles for SecEd via

Further information & research

  • Prevalence of insufficient, borderline, and optimal hours of sleep among high school students – United States 2007, Eaton et al, Journal of Adolescent Health, April 2010.
  • Teens and Sleep, information from the National Sleep Foundation (US):
  • How much sleep do we really need? Information from the National Sleep Foundation (US):
  • Sleep in adolescents: The perfect storm, Carskadon, Pediatric Clinics of North America, June 2011:
  • Frontline interview: Mary Carskadon, PBS:
  • Teensleep Project, Nuffield Department of Clinical Neurosciences:
  • Overnight therapy? The role of sleep in emotional brain processing, van der Helm & Walker, Psychological Bulletin, September 2009.
  • Insufficient sleep in adolescents and young adults, Judith Owens, Adolescent Sleep Working Group, American Academy of Pediatrics, September 2014:
  • Later teen bedtimes tied to school problems and distress, Jegtvig, Reuters, 2013:
  • Sleepmore in Seattle: Later school start times are associated with more sleep and better performance in high school students, Dunster et al, Science Advances, December 2018.
  • Synchronizing education to adolescent biology: ‘Let teens sleep, start school later’, Kelley et al, Learning, Media and Technology, August 2014:
  • MPs to debate late school starts for teenagers, BBC, February 2019:


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