Parents of children and teenagers have long been warned about the dangers of screen time and digital devices before bed - the worry being that screens could harm the sleep patterns of young people.
Author
Rachael Taylor
Professor, Department of Medicine, University of Otago
But do screens really hurt the length and quality of sleep?
Our new research (link to come) found that using screens in bed was worse for sleep than using screens for hours before going to bed.
Sleep guidelines recommend no screen use in the hour or two before bed. But we found screen time in the two hours before bed had little impact on young people's sleep. Instead, it was screen time once in bed that caused problems.
Using cameras to track device usage and sleep, we found using a device in bed could cause more harm than screen time right up to bedtime.
These findings challenge long-held assumptions about screen time at night and could help parents improve the quality of their children's sleep.
Connecting sleep and screens
A number of global organisations recommend adolescents stop using devices in the hour or two before bed, and instead undertake activities like reading a book or quiet time with the family.
But these recommendations are based on research with a number of limitations. The studies were designed in such a way that researchers could link sleep and screens. But they don't tell us if changes in how young people used screens had an affect on the length or quality of sleep.
Most of the existing research also used questionnaires to assess both screen time and sleep. Questionnaires are unlikely to capture true screen time accurately, particularly if you are interested in knowing more than just how long an adolescent has spent on their device.
To address some of these weaknesses in the previous research, we asked 85 adolescents aged between 11 and 14 to wear a body camera on their chest for the three hours before bed, for four nights.
These cameras faced outwards and accurately captured when, what and how adolescents used their screens. Because we were interested in overnight screen time as well, a second infrared camera was placed on a tripod in the teenagers bedroom and captured their screen time while in bed. The research participants also wore an actigraph - a watch-sized device that objectively measured screen time.
Teen nighttime activity
It quickly became obvious the adolescents spent a lot of their screen time while in bed.
Our analysis looked at two time periods - from the two hours before they got into bed, and from once they were in bed (clearly under the covers) until they put their devices down and were clearly trying to go to sleep.
Our data showed 99% of the adolescents used screens in the two hours before bed, more than half once they were in bed, and a third even after first trying to go to sleep for the night. Just one teenager did not use screens before bed on any of the four nights.
The screen time before they got into bed had little impact on their sleep that night. However, screen time once in bed did impair their sleep. It stopped them from going to sleep for about half an hour, and reduced the amount of sleep they got that night.
This was particularly true for more interactive screen activities like gaming and multitasking - when they use more than one device at the same time (like watching a movie on Netflix on a laptop while playing Xbox on a gaming device).
In fact, every additional ten minutes of this type of screen time reduced the amount of sleep they got that night by almost the same amount - nine minutes.
Revisiting guidelines
Our research was an observational study looking at the established screen habits of young people.
The next step to better understanding this will be to conduct experiments that can actually prove different types and timings of screen time affect sleep.
That said, what we have already found challenges existing guidelines. Screens at night may not be the bogey man they have been made out to be. But allowing young people to have screens in bed can be detrimental to their quality of sleep.
So the simple message might be to keep those devices out of the bedroom.
Rachael Taylor receives funding from Lottery Health New Zealand.
