Adolescents Benefit from Later School Start Times

A group of researchers from the Centers for Disease Control and Prevention, Sleep Research Society, American Academy of Sleep Medicine, and the American Academy of Dental Sleep Medicine performed an analysis of scientific literature around high school students’ sleep habits and performance.  They found that the later the high school start time, the better performance in teens, including fewer car accidents and longer sleep durations during the week.

This research was conducted to look at 18 peer-reviewed medical studies that were published before April 2016.  The goal was to evaluate sleep duration during the week in adolescents.  They found that duration increased by about 19 minutes when school started an hour later than usual.  Additionally, with the later start time, regular sleep time on school nights was about 53 minutes longer.  Furthermore, increased sleep because of later school start times led to fewer car accidents, less fluctuation in sleep duration between weekdays and weekends, and less daytime sleepiness.

Lead author of the research, Dr. Timothy Morgenthaler, professor of medicine at Mayo Clinic in Rochester, Minnesota and past president at AASM notes that the review was done to highlight the importance of evaluating the connection between high school student health and performance and later school start times.  There is a common belief that early school start times are a big reason students do not get enough sleep.  To add to that, the CDC did a study that found over 85% of American high schools had a start time before 8:30 a.m., which is the earliest time recommended by the AAP (American Academy of Pediatrics).

The analysis results were published in the December issue of the Journal of Clinical Sleep Medicine.

AASM recommends regularly getting 8 to 10 hours of sleep each night for teens between 13 and 18 years of age.  On the other hand, CDC studies show that more than 69% of teens get less than 8 hours of sleep on school nights.  AASM notes there is a natural circadian or biological “clock” shift that happens during pubescent years, leading to a preference for later nights, which clearly can conflict with early school times.

Dr. Morgenthaler reminds us that this nation’s future depends greatly on the mental, educational, and physical excellence of our youth, but the most recent surveys show that less than 1/3 of teens are getting enough sleep each night as recommended by leading medical authorities.  This is so concerning because sleep deprivation is directly linked to declining mental health, learning disabilities, focus problems, higher obesity rates, greater car accident rates, and even increased use of alcohol and drugs.

Ten of the 18 studies were cross-sectional, seven were prospective, and one was retrospective and historical; this qualifies the meta-analysis for systematic review, making the findings even more important and significant.  The majority of the studies looked at public schools, with just two being boarding schools.

There was mixed support that these findings show delayed start times at high school may improve grades or standardized test scores; however, further information in the study suggests that later school start times decreased school absences and tardiness.  Furthermore, having later school times may improve behavioral health as well.

Authors note that more studies are necessary to better examine the effects of later school start times.


Rachael Herman is a professional writer with an extensive background in medical writing, research, and language development. Her hobbies include reading, traveling, and cooking.


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