BOSTON – Teenagers slept more hours when they started school later, a new study found.
With 73% of high schoolers reporting receiving less than the recommended 8 hours of sleep per night, teens are among the most sleep-deprived members of society.
In this study, the later a teenager started school, the later he or she woke up, with average wake-up times having been just after 6:00 a.m. for those starting school between 7:00 and 7:30 a.m. and about 7:00 a.m. for those starting school after 8:30 a.m. But only those teens who started after 8:30 a.m. achieved the 8-hour recommended sleep duration, said Nicole Nahmod, during a presentation at the annual meeting of the Associated Professional Sleep Societies.
The students with the later school start times averaged 32 minutes of extra sleep, when compared with their early-rising colleagues, noted Ms. Nahmod, who is one of the study’s authors, a research technician, and study coordinator at Pennsylvania State University, Hershey. Specifically, adolescents who started school after 8:30 a.m. had a mean sleep duration of 8.1 hours, while those who started school earlier slept for only 7.5 hours a night.*
Nicole G. Nahmod
Acknowledging the importance of adequate sleep on teen health, mood, and school performance, the American Academy of Pediatrics recommends that middle schools and high schools begin at 8:30 a.m. or later. However, most school days start earlier than that, as evidenced by this dataset. While 72% of the study’s participants started school between 7:00 a.m. and 8:30 a.m., as many as 15% of the study participants began school during the narrower 7:00-7:30 a.m. window.
In this study, researchers from Penn State used data from 413 adolescents (mean age, 15.4 years; 46% male), who participated in a substudy of the Fragile Families & Child Wellbeing Study conducted across 20 large American cities. The study oversampled nonmarried pregnant mothers, resulting in a racially diverse sample and a high proportion of low-income families. The household income for 29% of the sample was below the poverty line.*
For this substudy, sleep duration was calculated from app-based daily diary reports of bed times, wake times, and school start times on days when a teen attended school.
The study was limited by its cross-sectional nature, but was enriched by a diverse range of school start times sampled from 20 U.S. cities, the high proportion of at-risk teens, and the use of a daily sleep diary.
“Current literature shows associations between later school start times and academic success, mood, and health. It also shows a decrease in motor vehicle accidents, tardiness, school dropout, and daytime sleepiness,” Ms. Nahmod noted.
Her continued research in this area involves analyzing the relationships between actigraphically assessed sleep measures in students and school start times.
Ms. Nahmod reported having no financial disclosures.
*This article was updated on June 6, 2017.