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A new study released this week in the journal Sleep found that later school start times for middle and high school students led to a significant increase in their sleep. Nearly 1 in 10 high school students reported higher sleep quality with a later start time, while 1 in 5 high schoolers reported a reduction in daytime sleepiness.
Previous studies have examined the impact of later school start times on students’ sleep, however, this study is notable for its size and duration. Researchers surveyed approximately 28,000 K-12 students in a suburban Denver, CO, school district, and followed them for three years — one year prior to a school start time shift, and then for two years post-change.
|Age||Average Daily Sleep Post-Change||Average Weekly Sleep Post-Change|
(14-18 years old)
|+ 43-52 minutes||+ 4 hours|
(11-14 years old)
|+ 30 minutes||+ 2.5 hours|
(5-11 years old)
|– 11 minutes||n/a|
Researchers found later start times had the greatest impact on high school students, who reported start times after 8:30am led to an average of 43-52 minutes of additional sleep per night. The survey data showed that while weekday bedtimes remained largely consistent (with a shift of about 14 minutes later), weekday wake times were as much as 60 minutes later than prior to the start time change. On average, high schoolers gained nearly four additional hours of sleep per week, which also helped decrease weekend “oversleep” to make-up for the sleep loss during their week.
Middle school students also reported an increase in sleep duration, though not as dramatic as high schoolers. These students reported going to bed about nine minutes later and waking up about 37 minutes later than before the shift, which led to middle schoolers gaining nearly 30 minutes of additional sleep per night — nearly 2.5 hours total per week.
Elementary school students saw the least disruption to their sleep schedule. To accommodate the later start times of high school and middle school students, the district shifted elementary school start times to a full 60 minutes earlier. While these students shifted to an earlier bedtime and wake time, this group (and their parents) reported a nominal reduction in overall sleep (approximately 11 minutes), but it wasn’t significant enough to lead to daytime sleepiness in these kids.
While additional research needs to be done on how these shifts might impact more racially and economically diverse school districts, the findings suggest that aligning school start times with student circadian rhythms can make a big difference for teenagers.