Many parents are concerned that their teens are sleep deprived and that this will affect their academic performance, but how much do they really need? Eric Eide and Mark Showalter reveal their findings
MANY PARENTS ARE TROUBLED that their children, especially teenagers, are sleep deprived. There is a natural worry that teens are sabotaging their current school performance and future opportunities for educational success by sleeping too little. Research suggesting a link between sleepiness and behavioral problems is also a cause of great concern for both parents and teachers.
|What we know|
|● Few teens get the recommended hours of sleep a night.
● Older teens who sleep 7 hours a night tend to have the highest test scores.
● Teens who sleep less than 6 hours a night or more than 11 hours tend to do poorly on tests.
National recommendations in the U.S. are that children and teens should get 9.25 hours of sleep a night. This is based on ground-breaking research conducted at Stanford University in the 1970s which found that children and adolescents naturally tend to get 9–10 hours of sleep each night when there are few distractions. Surveys suggest that few children and a tiny fraction of teens get that much sleep, especially on school nights, so should this be a matter of concern?
There are many potential reasons for children to not get the recommended amount of sleep. One reason is of particular relevance to educators: an hour spent sleeping is an hour not studying. As with most good things, there is a trade-off. Although a teenager might want additional sleep, a student who follows the recommendations would potentially have 10–14 fewer hours of time a week than a student who got the average amount of reported sleep for older teens of about 7 hours. Perhaps those extra hours would be spent playing video games or hanging out with friends. But it also means there is substantially less time for homework, projects, test preparation, and participation in extracurricular activities that can be important for college admissions.
Although there is clear evidence from other studies that severe sleep deprivation can significantly impair mental functioning, the impact of lower amounts of sleep loss is less clear. In order to understand more fully how sleep impacts young people, we studied the interaction of sleep and student performance on math and reading tests and how that interaction changes with age.
Data and methods
The data for our study come from the Child Development Supplement (CDS) of the Panel Study of Income Dynamics (PSID), administered by the Survey Research Center at the University of Michigan (psidonline.isr.umich.edu). These are nationally representative data designed to explore socio-demographic, psychological, and economic aspects of childhood and child development. We used data from interviews with 2,019 families in 2002–2003, providing information on 1,724 children and adolescents aged 10 to 19. This data was designed to collect information concerning the development of human capital in children and adolescents, and contains a rich set of variables for both the child and the family. The outcomes we focused on were math and reading scores on standardized tests. The tests were administered by the organization collecting the survey data and are used as a measure of academic performance. The sleep variable is a self-reported answer to the question: “How many hours of sleep do you usually get a night?” Our statistical analysis estimates:
- How differences in hours of student sleep are correlated with differences in math and reading test scores.
- How the relationship between sleep and average test scores varies between age groups.
- How demographic and economic factors affect the relationship between sleep and test scores.
The hours of sleep correlated with highest average test scores are quite similar across the math and reading tests. We also observed a clear pattern of declining sleep hours across age groups. For example:
● 10-year-olds: 9 to 9.5 hours of sleep per night are associated with the highest average test scores.
● 12-year-olds: 8 to 8.5 hours of sleep per night are associated with the highest average test scores.
● 16-year-olds: About 7 hours of sleep per night are associated with the highest average test scores.
Importantly, we also found that average test scores do not change dramatically across a relatively large range of reported sleep hours. For example, for older teens, 16–18 years old, sleeping 7 hours is not much different than sleeping 9 hours in terms of predicted test score performance. But declines in performance become more dramatic at the extremes: substantially below 6 hours of sleep, or above 11 hours.
What does this mean?
Our findings offer some reassurance for parents – students can do very well academically with less sleep than was previously thought. The results are tempered by additional evidence in our research that substantial sleep loss, for example, a 16-year-old getting less than 6 hours a night, or excessive sleep, that same teen getting over 11 hours a night, are associated with significant declines in test score performance. Sleep does matter!
One question that arises is why our results differ from the studies that led to the national guidelines. A key difference between our study and how the national guidelines were determined is that we observe what students actually do in the home, not what they do in a strictly controlled laboratory setting. In the laboratory setting, children are not faced with the choice of whether to study or to sleep, whereas at home during the school year that choice is a fact of life. We do not view these two approaches as incompatible, but they do give different perspectives on how sleep affects student outcomes. We find that the relation between sleep and test score performance is more nuanced than previously thought. There appears to be a range of sleep hours that are consistent with good performance on exams, and that this range tends to decline with the age of the student.
Related to that point is the common perception that more sleep is always preferred to less. When it comes to academic performance, that notion is unlikely to be true. More sleep comes at a cost in terms of less time to spend on studying and other productive activity. This implies that there is a balance to be found. The exact nature of that balance is likely to vary somewhat from student to student. We do observe a substantial amount of individual variation in our data: there are some students who can score high on exams with low hours of sleep and others who do fine with more hours of sleep. But the “average” or “typical” older teen evidently finds that balance at about 7 hours of sleep.
There is certainly much yet to be explored and important qualifications to make concerning our results. Our work does not explore the link between sleep and overall physical and mental health, or between sleep and behavioral problems. We also do not consider the effects of daytime sleep (napping) on academic performance or its link with nighttime sleep. Nor do we account for the timing of nighttime sleep, which has had an important role in the discussion of school start times. These and other related issues offer fruitful avenues for further investigation.
About the authors
Eric R. Eide is the department chair and a professor of economics at Brigham Young University. His research focuses on how health factors influence education outcomes. He previously worked as an economist for the RAND Corporation assisting with education reform in Qatar. Mark H. Showalter is a professor of economics at Brigham Young University. He served as senior economist on the President’s Council of Economic Advisers in 2003–2004 and is an associate editor at the journal Economics of Education Review.
Eide ER, and Showalter MH (2012), Sleep and Student Achievement, Eastern Economic Journal, advance online publication, January, 2012.
Mitru G, Millrood D, and Mateika JH (2002), The Impact of Sleep on Learning and Behavior in Adolescents, Teachers College Record, 104, 704–726.
National Sleep Foundation (2000), Adolescent Sleep Needs and Patterns: Research Report and Resource Guide, Washington, DC.
Wolfson AR, and Carskadon MA (2003), Understanding Adolescents’ Sleep Patterns and School Performance: A Critical Appraisal, Sleep Medicine Reviews, 7, 491–506.
Matricciani LA, Olds TS, Blunden S, Rigney G, and Williams MT (2012), Never Enough Sleep: A Brief History of Sleep, Recommendations for Children, Pediatrics,129 (3), 548–556.