In fall of 2016, Seattle Public Schools announced they would shift high school start times from 7:50am to 8:45am, a delay of almost one hour. The hope was that later start times would allow high school students to get more sleep. At the time, parents had mixed reactions and school districts across the country waited in anticipation for potential impacts. No one knew how teens would react, so UW Biology Professor Horacio de la Iglesia and graduate student Gideon Dunster decided to find out. Over the course of two years, Horacio and Gideon conducted a study at Franklin High School and Roosevelt High School to study sleep, behavior, and circadian rhythms in affected high school students.
So, what were the results? It turns out that teens do indeed get more sleep with later start times. Not only that, later start times were correlated with improved academic performance and attendance as well.
Laying the groundwork for a dramatic policy change
For five years, a coalition of grassroots education advocates lobbied the school board to delay start times for secondary schools. Horacio joined a growing network of Seattle parents, teachers, and students to push for change. The literature on sleep medicine suggested that delayed start times would benefit teens by improving their sleep and kicking off a cascade of positive health benefits. After five years, Seattle Public Schools decided to take the leap.
Conducting the experiment
Horacio quickly realized that the new policy change provided a unique opportunity to study the effects of delayed start times in real-time. By studying students before and after the change, his lab would be able to monitor the effects of a widely debated policy. In order to collect preliminary data (before the change went into effect), Horacio and Gideon moved quickly to plan an experiment in the span of a few months. Fortunately, Horacio and Gideon had prior experience monitoring sleep in field studies and had already built connections with local high schools.
Two teachers at Roosevelt High School and one at Franklin High School agreed to allow Horacio and Gideon access to their classrooms – three cohorts per year totaling around 90 students. Horacio and Gideon visited each classroom and used fitness watches and sleep diaries to collect data over a two-week span.
Every time Horacio and Gideon visited a new classroom, they gave an introductory lecture on the biology of sleep. They also distributed demographic surveys, issued fitness watches, and provided instructions for the teens’ sleep diaries. For the next two weeks, students from one period would log data points about their sleep and wake-up times in their sleep diaries. When students from period 1 were done, they would download the data and hand the watches out again for period 3. The watches collected data related to light exposure levels and motion to confirm sleep diary entries. At the end of six weeks and three periods, Horacio and Gideon would give all students access to their own data and share a preliminary data analysis. They repeated their data collection for all three classes and returned again the next year – after school start times were pushed back.
The results of the sleep study
After spending a year on the data analysis, Horacio and Gideon found that teens got more sleep with delayed start times. Students reported being less tired and showed improved academic performance. Students from Franklin, which serves a majority of students from lower socioeconomic backgrounds, reported increased attendance, which began an important conversation around equity - that delayed start times could disproportionately benefit low-income students.
A teenager’s bedtime is biologically determined, but the time they wake up is dictated by their school. When schools delay start times, the new school schedules align far better with their students’ natural circadian rhythms. And getting more sleep provides an array of health improvements.
So what’s next? Horacio says his lab would be interested to see if the trend holds, perhaps conducting a similar study in the future. He would also like to see more school districts emulating Seattle Public Schools and collaborating with sleep experts on circadian biology. There is a huge sleep deprivation epidemic in the United States and we can do much more to understand and to help address the issue.
*A special thank you to the UW Biology Riddiford-Truman Award for providing funding at a critical time during this study.