Nick Carne
Starting the school day later means teenagers get more sleep, perform better academically and and in some cases are more punctual, a US study suggests.
Researchers from the University of Washington (UW) and the Salk Institute for Biological Studies monitored students at two Seattle high schools before and after 18 schools in the district moved the opening bell from 7.50am to 8.45am, and found that 34 of those extra 55 minutes were spent asleep.
That boosted the total amount of sleep on school-nights from a median of six hours and 50 minutes to seven hours and 24 minutes, bringing it closer to the suggested minimum of eight hours for teenagers. It was associated with a 4.5% increase in the median grades of students across both schools.
At one school, considered to be economically disadvantaged, there were also significantly fewer instances of late arrivals and absenteeism.
The reason is linked to the fact that teenagers don’t just choose to stay up late – they are wired that way. Thus, they’d like more morning sleep, if given the opportunity.
And that’s just what the study found. The participants didn’t stay up even later; they merely took advantage of the chance to sleep longer.
The researchers say that is consistent with the natural biological rhythms of adolescents, which are quite different to those of adults and young children.
“All of the studies of adolescent sleep patterns in the United States are showing that the time at which teens generally fall asleep is biologically determined, but the time at which they wake up is socially determined,” says UW’s Gideon Dunster.
“This has severe consequences for health and wellbeing, because disrupted circadian rhythms can adversely affect digestion, heart rate, body temperature, immune system function, attention span and mental health.”
In their study, which is reported in a paper published in in the journal Science Advances, Dunster and colleagues used wrist activity monitors rather than relying solely on self-reported sleep patterns.
Ninety-two students drawn from both schools wore the monitors all day for two-week periods in the spring of 2016, when school still started at 7:50 am, and a second group of 88 wore them for a similar period in 2017, about seven months after school starting times shifted later.
The monitors gathered information about light and activity levels every 15 seconds, but no physiological data about the students, and the researchers used this to determine when the students were awake and asleep.
And they were surprised by the findings. “Thirty-four minutes of extra sleep each night is a huge impact to see from a single intervention,” co-author Horacio de la Iglesia comments.
