(Reuters Health) – Allowing teens to start school just 10 minutes later each day can help them get more than 20 minutes of extra sleep on a typical night, a Canadian study shows.
While that might not sound like much, for some sleep-deprived teenagers there might be enough difference to help them get the recommended minimum of eight hours of sleep a night, researchers noted in Sleep Medicine.
"Our body's circadian hours naturally shift later in puberty, so teenagers get tired tonight (due to the release of melatonin later) and therefore, need to sleep longer in the morning to get enough rest," wrote study author Karen Patte of Brock University in Ontario said in an email.
"The delayed start time (school) has been recommended for adolescents to adjust to their delayed sleep schedule," Brock said. "This study shows how sensitive student sleep is to school schedules."
Inadequate sleep increases the risk of accidents and injuries in adolescents, obesity, poor eating habits, drug use, emotional problems and deficits in school attention, focus and achievement, Brock said.
Canadian guidelines recommend at least 9 hours of sleep per night for children aged 5 to 13 years and at least 8 hours for teens aged 14 to 17. For this study, the researchers tested data in adolescents in ninth grade to 12 in 49 Ontario secondary schools from 2012 to 2017.
Under the Canadian guidelines, children aged 5 to 13 must sleep at least nine hours a night and adolescents aged 14 to 17 must get at least eight hours. For this study, researchers examined data on adolescents in ninth grade to 12 in 49 Ontario schools from 2012 to 2017.
Every year, researchers survey schools about the start time and about how much sleep, screen time and exercise they get.
At first, students reported sleeping on average seven hours a day, with an average of 8.2 hours of total screen time and around 2 hours of moderate to strong physical activity.
School start hours start at 8am to 9:35 a.m.
During the study period, 11 out of 49 schools changed starting times, including three schools that did it twice.
Three schools delayed their start time by 5 minutes at several points during the study, and three pushed back their starting time 10 minutes, analysis was found.
While delaying schooling starting with 5 minutes does not appear to make a meaningful difference in how much teenagers sleep, students who get a delay of 10 minutes on average sleep 23.7 minutes longer than they did before the delay, the researchers report in Sleep Medicine.
In addition, two schools moved from 5 minutes and five schools changed the start time to take students in the previous 10 minutes.
Initially it appeared to produce less exercise, the study found.
When school starts 5 minutes before, students get an average of 8 minutes less exercise a day than children in school with consistent start time.
But when students switch to starting time 5 minutes later, they get an average of almost 11 minutes more exercise a day when the new start time is 8:15 or 8:20. In other schools with delayed start times, however, they lack exercise in normal days.
This study is not a controlled experiment designed to prove whether or how changes at the start of school can directly affect student sleep time, playtime or sports time. Another limitation is that schools were not randomly selected to change the time to start school, the study authors noted.
Even so, the results offer new evidence that even small delays at the start of school can have a positive impact on student sleep – with minimal disruption to school schedules – said Dr. Heather Manson, head of health promotion, chronic illness and prevention of injuries at Public Health Ontario.
"Compared to longer delays, a 10-minute delay might be more feasible to apply at the school level," Manson, who was not involved in the study, said via email.
SOURCE: bit.ly/2KoqhEW Sleeping Medicine, online October 12, 2018.