The new data shows students get more sleep and report having more time to do their schoolwork when the first bell of the day is later.
The idea that middle school and high school students will do better in school if they get more sleep and aren’t chronically sleep-deprived sounds pretty intuitive, right? A growing body of research suggests one way to achieve this is to push school start times later.
The evidence led the American Academy of Sleep Medicine (AASM) to issue a position statement in April 2017 recommending start times of 8:30 a.m. or later be implemented for middle schools and high schools. According to a report published in August 2015 by the Centers for Disease Control and Prevention (CDC), which measured school start times across the United States for the 2011–2012 school year, only 14 percent of high schools and 19 percent of middle schools met that recommendation.
Now the largest study yet to look at this issue, which followed 15,700 students, suggests that both middle and high school students got more sleep and were less likely to feel too sleepy to do homework after their district pushed school start times later — by 50 minutes for middle school students and by 70 minutes for high school students. The data is considered preliminary because the researchers will continue to follow 5,000 of the students to analyze the effect of the change on students’ academic performance in the next two years.
The research was published in an abstract in the April 2019 issue of the journal Sleep, and it will be presented this week in San Antonio at Sleep 2019, the annual meeting of the Associated Professional Sleep Societies (which includes both the AASM and the Sleep Research Society).
The responses from the students have been overwhelmingly positive, says Lisa J. Meltzer, PhD, the associate director of pediatrics at National Jewish Health in Denver, Colorado, and the lead investigator of the study. “Overall, students felt that they were happier and that their friends were happier. They reported feeling more alert throughout the day, especially during the first period, and they were more engaged in the classroom.”
Students Got More Sleep After School Start Times Were Delayed
The data for the new study comes from the Cherry Creek School District in Greenwood Village, Colorado, which changed school start times for the 2017–2018 school year for middle school from 8 a.m. to 8:50 a.m. and for high school from 7:10 a.m. to 8:20 a.m. This decision was the result of over 18 months of community meetings and deliberation by the various community leaders and stakeholders, Dr. Meltzer says.
A total of 15,700 students completed online surveys in spring 2017 before the start time change, and 18,607 completed surveys after the start time change. The surveys asked questions about weekday and weekend bedtimes, wake times, total sleep time per night, extracurricular activity participation, sleepiness during homework, and academic engagement.
The survey data showed all students went to bed slightly later after the delayed start: The middle school students went to bed 8 minutes later on average; and high school students’ bed times were 13 minutes later. Total sleep time, however, increased. Middle school students woke up 38 minutes later on average, increasing their average nightly sleep time by 31 minutes. High school students woke up 58 minutes later, sleeping on average 48 minutes longer per night.
The change affected the students’ self-reported levels of sleepiness during the day and engagement in activities. The data showed:
- 44 percent of middle school students slept at least 9 hours, compared with only 38 percent before the school start time change.
- The number of high school students who were able to get 8 or more hours of sleep more than doubled, increasing to 58 percent after the change (from 27 percent before it).
- Scores on students’ self-reported levels of academic engagement (behaviors like participating in first period) were significantly higher after the start time change for all students.
- The number of students who said they felt too sleepy to do their homework fell from 46 percent to 35 percent for middle school students after the change, and from 71 to 56 percent for high school students.
Finally, the change seemed to have little impact on life after school. Critics of delaying school start times have been concerned students would engage less in after-school activities if school started and ended later, Meltzer says. The new data shows middle school participation in sports decreased by 8 percent after the change. Participation in high school sports shrank by less than 3 percent. Participation in other activities for both middle school and high school students decreased by less than 3 percent. And employment for high school students shrank by less than 3 percent.
One limitation of the data is the fact that, though the study population is a large one, all the data come from one school district. Additionally, the data comes from self-reported survey data, rather than being objectively measured, Meltzer notes.
The Study Isn’t the First to Show Later School Start Times Improve Sleep and Performance, but It’s One of the Biggest Data Sets on the Topic
“This research shows that this relatively small change made a very positive impact,” says Alon Y. Avidan, MD, MPH, a professor of neurology at the David Geffen School of Medicine at UCLA and the director of the UCLA Sleep Disorders Center, who was not involved in this research. The students reported being able to finish more schoolwork, and they reported getting more sleep, which is a really critical issue, he says.
The AASM sleep recommendations state that children 6 to 12 years old should sleep 9 to 12 hours at night, and teenagers ages 13 to 18 should sleep 8 to 10 hours a night. Yet data gathered in a 2015 CDC survey that included children from across nine states found that about 6 in 10 middle school students and 7 in 10 high school students are falling short on sleep on school nights. In addition to how this less-than-optimal sleep affects school performance, lack of sleep also increases the risk of obesity, depressive symptoms, drinking alcohol, smoking tobacco, and using illicit drugs, according to the CDC.
The new study isn’t the first to demonstrate that delaying school start times can have positive effects. Previous studies prompted the AASM to issue its 2017 statement urging schools across the United States to take such steps.
But the new study is one of the biggest. “This study is very large, with more than 15,000 students completing surveys. We’re talking about a huge power in terms of statistical significance,” says Dr. Avidan.
A study published in December of 2018 in the journal Science Advances found similar results in increased sleep times and less sleepiness in students by using activity trackers, for example, but included fewer than 200 participants.
Researchers Will Continue to Track How Later Starts Affect Students’ Academic Performance
The large scale of this project is just one factor that makes it different from other research on what happens when school start times are delayed, Meltzer says. In addition to the thousands of surveys that students will continue to complete over the next couple of years, researchers have obtained permission from more than 5,000 parents to link the data obtained in the survey with academic outcomes. “We’ll be able to follow the trajectory of those students year over year,” Meltzer explains.
This study reports the initial impact the delayed start has had on students (as measured by the surveys), but researchers plan to release further findings on data collected in surveys from parents, teachers, and focus groups, as well as district level and community level data.
“So far everything we’ve found across all these pieces completely supports what previous research has shown, which is that healthy school start times is incredibly beneficial for students,” Meltzer says.
Physiological Factors Unique to Older Adolescents and Teens May Explain Why Later School Start Times Are Beneficial
Adolescents go through puberty, usually starting sometime during middle school and continuing in high school, Meltzer says. Puberty is associated with hormone changes. One hormone that is affected is melatonin, a naturally produced hormone that regulates our sleep and wake cycles. “Melatonin is released when it’s dark and prepares our body for sleep. Bright light in the morning tells our body to stop making melatonin and wake up,” Meltzer says.
When adolescents go through puberty the timing of when melatonin gets released is delayed by about 1 to 2 hours, Meltzer explains. “What that means is that it’s very difficult for teens to fall asleep early and to wake up early. When we ask them to wake up and go to school early, it’s at a time when their brain is basically biologically asleep,” she says.
That’s why getting up early is more difficult and has a greater impact on middle and high school students than it does for adults, she adds.
“This research shows that when you align the circadian rhythms and you make them more harmonious with the sleep/wake patterns, you’re giving students more time to do work and get sufficient sleep,” adds Avidan.
The Barriers Standing in the Way of Later School Start Times Aren’t Prioritizing Students’ Needs and Well-Being
“It’s not ground-breaking or earth-shattering to know that this [delaying of school start times] really works,” says Meltzer. “I don’t think it’s lack of science holding districts back from making start times later. It’s the difficulty with change.”
But the new data from this Colorado school district shows that people can adapt to this change, she says. People and systems can adjust and it doesn’t negatively impact aspects of students’ lives in significant ways, including when you look at extracurricular activities and employment, she adds.
Barriers school districts face in moving start times include: costs associated with the change, impacts to the parents’ work schedules, and traffic, Meltzer says.
But prioritizing those barriers discounts the needs and well-being of students. “We change school start times to benefit the health and well-being of our students,” says Meltzer. “This is a critical decision for school districts to make.”
Becky Upham
APR