Until recently, sleep guidelines recommended no screen use in the hour or two before bed.
But new research by University of Otago Edgar Diabetes and Obesity Research Centre dietitian and researcher Dr Bradley Brosnan has found it is screen time once in bed that is causing the problems.
"Screens before bed might not be as bad as you think. Really, the culprit is once you get into bed and use them.
"There’s two reasons for that. The more screen time you have, the more it cuts into sleep time — you can’t have both.
"The second reason is, the more stimulating activities that you’re doing — like gaming, chatting with friends or swiping through social media — the harder it makes it to get to sleep.
"A lot of adolescents are not getting the sleep that they really need."
Dr Brosnan said a lack of sleep impacted how people moved, ate and felt — particularly for teenagers who were still developing and growing physically and mentally.
"We need to protect their sleep as much as we can."
He said a "simple" sleep guideline in theory would be for devices to be kept out of the bedroom, allowing teenagers to use their devices before bed, but not in bed.
He said screen time was a mainstay in adolescents’ bedtime routines, and sleep guidelines needed to be re-evaluated to better reflect modern life.
"We need to revisit sleep guidelines, so they fit the world we live in, and actually make sense.
"The current ones aren’t achievable or appropriate for how we live."
The study involved 85 adolescents, aged 11-14, wearing body cameras on their chests from three hours before bed until they got into bed, over the course of one week.
Along with the body camera capturing when, what and how they used their screens, a second infrared camera was placed in their bedrooms to capture their screen time while in bed.
They also wore an actigraph — a watch-sized device which measured sleep.
The researchers found 99% of participants used screens in the two hours before bed, more than half used screens once in bed, and a-third used them after first trying to go to sleep for the night.
"Our most interesting findings were that this screen time before they got into bed had little impact on 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.
To help parents manage their children’s screen time, Dr Brosnan has been developing screenwise.co.nz, an online platform providing realistic, evidence-based tips and tools that parents can easily incorporate into their daily routines.
