In October of 2014, on this very blog, I wrote about the new AAP policy statement calling for delayed school start times for adolescents. I agreed with their labeling of insufficient sleep as “one of the most common, important, and potentially remediable health risks in children”, and I still do. Since that post, the evidence in support of pushing start times back to at least 8:30 AM has continued to mount.

A new study involving children in the Seattle School District was published on Wednesday in Science Advances, and it has been making the rounds in various medias. It gives us even more data to support efforts to improve teen sleep by allowing extra time in the morning. Not only did it show that the extra time resulted in more overall sleep, because there has been some concern that kids will just stay up later, but it also had academic benefits. I’ll discuss the study shortly, but first a brief recap of concerns regarding teen sleep deprivation.

What are the common adolescent sleep challenges?

Teenagers these days are often fighting an uphill battle when it comes to getting adequate sleep, which is considered by most sleep experts to be in the 8.5 to 9.5 hours per night range. Some teens do well with less than the recommended amount of sleep, but for far too many it adversely affects school performance and can even lead to long-term mental and physical health problems. It also increases the risk of traffic accidents and fatalities.

Technology is one of the most obvious reasons why older children are getting less sleep. Most of them have electronic media in their rooms, if not attached to their bodies in the form of a smart phone, at all times. The evidence is clear that the internet and social media are a major factor in delayed sleep initiation. Popular energy drinks, with their large amounts of caffeine and other stimulants, can also play a role.

From a biological perspective, among the many changes that a child undergoes with the onset of puberty is an alteration of the internal circadian rhythm and sleep drive. Most adolescents gradually shift towards favoring staying up later and subsequently sleeping later. Even without the influence of social media and caffeine, teens often have difficulty falling asleep before 11 PM and waking before 8 AM. With chronic insufficient sleep, a teen may not feel truly alert until after 10 AM. Again, there is variability between individuals but this affects the vast majority of even healthy teenagers.

It is the combination of multiple factors, such as those discussed above, but also including the need to wake up earlier on weekdays for school, that leads to a buildup of daytime fatigue. Many teenagers will try to catch up on the weekends or holidays. While this is a manifestation of their underlying biological sleep preference, it is also driven by sleep pressure accumulated during the week. It doesn’t actually solve the problem, and may make it harder for teens to adjust sleep cycles over the long haul.

How common is insufficient sleep in adolescents?

According to the technical report that accompanied the 2014 AAP policy statement, the concern that teenagers are not getting enough sleep is based on solid epidemiological data, and is likely even underestimated because self and parent reporting tends to overestimate actual hours slept. With that in mind, the 2006 National Sleep Foundation Sleep in America Poll revealed that 3 out of 4 kids average less than 8 hours of sleep each night by their senior year. The 2014 NSF poll found that only 10% of children aged 15-17 get the recommended amount of sleep, and almost 60% get less than 7 hours.

These surveys and others reveal the fact that most teens feel tired at school, with many reporting episodes of falling asleep in class. Furthermore, most teens feel the need to compensate with stimulants and extra weekend sleep. Unfortunately, also per a number of surveys, parents are largely unaware of these issues and believe that their teenage children are getting the recommended amount of sleep.

How does insufficient sleep harm adolescents?

The list of potential harms from insufficient sleep in the adolescent population is long and varied, and includes both immediate and long term effects. The 2014 AAP report highlights three categories of negative effects: Physical health and safety, mental health and behavior, and school performance. I’ll highlight some of the major potential consequences in each.

Obesity and long term cardiovascular events like heart attacks and stroke have been linked to insufficient sleep starting in the teenage years. More acute is the major issue of “drowsy driving” and the risk of motor vehicle accidents, with 50,000 fatigue-related accidents occurring each year involving a driver under the age of 25. Increased consumption of caffeine, and potential associated toxicity, is clearly linked to poor sleep, but use of prescription stimulants that have been diverted from their intended indications is also a concern.

Teenagers with chronic inadequate sleep are more likely to have anxiety conditions and depression. They are also at risk for difficulties with impulse control and self-regulation, increasing risk-taking behaviors. Poor sleep can also interfere with the ability to process stress, which can exacerbate the likelihood of illness and maladaptive coping strategies. And not surprisingly, adequate sleep plays an important role in cognitive function, memory, and attention. Poor sleep thus can interfere with academic success, increase missed days of school, and lead to higher rates of dropping out.

More experts weight in

In April of 2017, the American Academy of Sleep Medicine published their policy statement on the subject of adolescent sleep and delayed school start times. It echoes the concerns of the AAP:

During adolescence, internal circadian rhythms and biological sleep drive change to result in later sleep and wake times. As a result of these changes, early middle school and high school start times curtail sleep, hamper a student’s preparedness to learn, negatively impact physical and mental health, and impair driving safety. Furthermore, a growing body of evidence shows that delaying school start times positively impacts student achievement, health, and safety.

They also point a lack of public awareness of sleep deprivation in teens and how school start times are partly to blame. Like the AAP, they also call for pushing start times back to at least 8:30 AM for older children.

Now back to the new study

In 2016, after significant community effort to address transportation logistics and scheduling of after school activities, start times in the Seattle School District middle and high schools were pushed back to 8:45 AM. Researchers at the University of Washington saw this as a golden opportunity. They could assess the amount of sleep students got both before and after the switch, as well as academic performance.

Students in the study got, on average, a bit more than 30 minutes of extra sleep each school night. This may seem trivial to some, although I bet most readers recognize how significant an extra half hour of sleep can be, particularly when it is consistent over a lengthy period of time. Improvements were seen in daytime sleepiness, grades, and tardiness, with the biggest effect in students in low socioeconomic groups. Although not studied, it is reasonable to consider that decreased sleep inertia would result in safer driving.

There were a couple interesting aspects of this study that I believe are worth pointing out. The first is that it didn’t rely only on each student’s recall of sleep amounts. Rather the study involved the use of wrist activity trackers to log sleep-wake cycles. Also, they employed a simple but clever method of determining if delaying school start time brought students more into alignment with their natural circadian timing and reduced social jet lag. As predicted, students had less discrepancy between sleep patterns on school and non-school nights.

Conclusion: What are we waiting for?

What the study cannot do is prove beyond all doubt that the increased sleep is what resulted in the improved outcomes. The students were not blinded. They knew that they were involved in the research and thus there could have been an observer effect. But data collected over the years certainly seems to be triangulating on the conclusion that if you allow kids to sleep more, they will do better in school and live healthier and safer lives.

Transitioning to later school start times can be challenging. It takes buy-in from schools, parents, and the community. But it can be done. As I said in 2014, it certainly appears to be worth a difficult transition period. We shouldn’t ignore other modifiable behaviors that interfere with adolescent sleep, however.


Posted by Clay Jones

Clay Jones, M.D. is a pediatrician and a regular contributor to the Science-Based Medicine blog. He primarily cares for healthy newborns and hospitalized children, and devotes his full time to educating pediatric residents and medical students. Dr. Jones first became aware of and interested in the incursion of pseudoscience into his chosen profession while completing his pediatric residency at Vanderbilt Children’s Hospital a decade ago. He has since focused his efforts on teaching the application of critical thinking and scientific skepticism to the practice of pediatric medicine. Dr. Jones has no conflicts of interest to disclose and no ties to the pharmaceutical industry. He can be found on Twitter as @SBMPediatrics and is the co-host of The Prism Podcast with fellow SBM contributor Grant Ritchey. The comments expressed by Dr. Jones are his own and do not represent the views or opinions of Newton-Wellesley Hospital or its administration.