CME Author: Zeena Nackerdien
Study Authors: Gideon P. Dunster, Luciano de la Iglesia, et al.
Target Audience and Goal Statement:
Sleep specialists and pediatricians
The goal is to learn more about a Seattle School District in a study designed to understand whether delaying secondary school start times would correlate with increased adolescent sleep duration and better academic performance.
For this study, the authors posed the following questions:
- Does an intervention result in adolescents getting more sleep?
- Can longer sleep duration be correlated with better academic performance and other outcomes?
To answer these questions, the Seattle School District conducted a pre- and post-study in which investigators measured sleep/wake cycles using wrist activity devices, and other tools, following the introduction of a later start time to the school day during the 2016-2017 academic year.
Synopsis and Perspective:
Healthy sleep has many components, such as sufficient duration, regular sleep-wake patterns, efficiency, alertness, and satisfaction. Depressed moods, risk-taking behaviors, heart disease risk, and obesity are among the negative consequences of irregular sleep-wake patterns and insufficient sleep patterns (<8 hours per night). Adverse physical and mental outcomes due to chronic sleep deprivation occur regardless of age, but are especially important because of the role normal sleep plays in learning and memory consolidation.
The recommended daily sleep duration for adolescents is 8 to 10 hours; 62% of high school students report insufficient sleep. The hormonal response to the 24-hour daily light/dark exposure that influences circadian rhythm is altered in adolescents, making them physiologically yearn to stay awake later at night and to remain asleep later in the day. Additionally, older adolescents are able to stay awake longer, compared with younger adolescents, due to a reduced sleep pressure during wake periods. Many other factors play a role in the findings of insufficient sleep, including chronotype (timing of daily activity) of the individual, changes in social life, and the use of electronic devices that may keep teenagers awake during the evening.
The 2014 School Health Policies and Practices Study showed that 93% of high schools and 83% of middle schools in the U.S. started school before 8:30 a.m. Because many adolescents are sleep-deprived, The American Academy of Pediatrics has recommended a later start date to the school day. But there are currently no objectively measured, long-term data, showing that a later school start time correlates with prolonged adolescent sleep time.
Horacio O. de la Iglesia, PhD, of the University of Washington in Seattle, and colleagues, worked with science teachers and sophomores (grade 10) of two public high schools in that city. Study participants wore wrist-watch monitors for 2 weeks to track activity, light exposure, and other measures of sleep hygiene. Sleep habits of sophomores were compared in spring 2016 before the school start time was shifted from 7:50 a.m. to 8:45 a.m. to spring 2017, after the instituted change.
Factors such as school, sex, depression index, and chronotype, did not emerge as significantly different between years. Non-school day sleep schedules and the number of naps between the 2 years also did not show significantly different changes; however, the pre- and post-research study showed that there was an increase in the daily median sleep duration of 34 minutes.
Survey findings suggested that students were less sleepy on those days, according to de la Iglesia and colleagues. Additionally, there was also a 4.5% increase in median student grades and an improvement in attendance as first-period absenteeism dropped from 15.5 to 13.6 per student-year (P<0.0001).
“Although it is highly likely that increased sleep was the cause for reduced sleepiness, it is much harder to attribute causality for 4.5% higher grades on increased sleep; nevertheless, it is certainly reasonable that students who are better rested and more alert should display better academic performance,” de la Iglesia told MedPage Today.
Study limitations include the lack of a control group due to the nature of the study, and the possibility that year-to-year improvements in exam scores and grades in the science classes may be due to unconscious bias regarding the impact of later start times.
Source Reference: Science Advances, Dec. 12, 2018; DOI:10.1126/sciadv.aau6200
Study Highlights: Explanation of Findings
Over the past century, sleep has shortened by about 1 hour in children. Some surveys have reported longer sleep times when the school start time is shifted to a later hour; however, there is no objectively recorded data showing that delaying the school start time prolongs daily sleep in adolescent students. Another short-term study showed that delaying the start time by 1 hour for a week resulted in a 1-hour gain of sleep when compared with themselves under the normal schedule and to non-delayed controls.
Many children do not get the recommended 9 hours of sleep per night during the school year. The investigators stated that, to the best of their knowledge, this is the first report to show that an across-the-district change in school start times resulted in a significant increase in objectively measured sleep. Lengthening the median sleep duration from 6 hours and 50 minutes to 7 hours and 24 minutes would bring society closer to restoring the historical sleep values present for several decades, before evenings within brightly lit environments and with access to light-emitting screens were common among teenagers, according to the authors.
Investigators also analyzed school-wide data for first-period punctuality and attendance. Compared with the high school in the more affluent area, the school in a poorer area had less tardiness and fewer absences after the change. This suggests that delaying high school start times could help close the learning gap between low and high socioeconomic groups.
“After the change was made. the two schools were much more similar to each other in terms of attendance and late arrival,” de la Iglesia said. “This suggests — although we can’t prove it yet — that delayed school start times could benefit lower-income students more and contribute to reducing the achievement gap. That is very exciting.”
A delayed start time of 55 minutes did not correspond to a sleep duration increment of 55 minutes. Most likely, other factors keep students up at night, so the researchers suggested that delayed school start times should be coupled with advice on sleep hygiene. For instance, students could be advised that the heightened use of screens late at night has been linked to a delay in falling asleep.
Although the findings appear to show a benefit to later high school start times, de la Iglesia said that it may take time for other large school systems to follow Seattle’s lead.
“One of the main obstacles is cultural — the idea that teens are sleeping later because they are lazy, which isn’t true. They are not lazy. They are just following their biological timing, and that isn’t going to change,” he said.
He added that economic and institutional obstacles have also prevented school systems from adopting later high school start times. Many school systems don’t have enough buses to make the change, and sports coaches have fought it because later start times mean later dismissals, which interfere with practice schedules.
“It is certainly not an easy thing to do, but it could have huge benefits,” de la Iglesia said. “It is pretty clear that high school students will get more sleep if school start times are later.”
Original story for MedPage Today by Salynn Boyles
Robert Jasmer, MD Associate Clinical Professor of Medicine, University of California, San Francisco and Dorothy Caputo, MA, BSN, RN, Nurse Planner