Screen time only appears to have an affect on sleep when used in bed, a new study has found. File photo. Photo: 123RF
Screen time in the two hours before bed has little impact on kids, but using phones and laptops in bed leads to a worse night's rest, according to a new study on children's sleep.
University of Otago researchers used body and infrared cameras to monitor the screen use and sleep of 85 children aged between 11 and 14 over a week.
They found 99 percent of the young people 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.
Lead author Dr Bradley Brosnan, of the Edgar Diabetes and Obesity Research Centre, said this was not surprising. But the most interesting finding was that screen time before they got into bed had little impact on their sleep.
"That was the most surprising and contradicts the current sleep hygiene guidelines which say no screens before bed. But we found that it's really about the timing of when you use screens," he said.
Researchers found the children's sleep was only affected if they used their devices in bed.
"That's when it can have a real impact, it's the closest time to when you're about to shut your eyes. So just trying to wind down during that time is really important," Brosnan said.
"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 more than one device was used at the same time, such as watching a movie on Netflix on a laptop while playing Xbox on a gaming device, he said.
Brosnan said every additional 10 minutes of this type of screen time reduced the amount of sleep they got that night by almost the same amount.
"Our findings suggest that the impact of screen time on sleep is primarily through time displacement delaying sleep onset rather than any direct effects of blue light or interactive engagement as we didn't find associations with sleep latency and wakefulness during the sleep period."
Brosnan recommended parents keep screens out of their children's bedrooms at night time.
"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."
"Perhaps a more practical strategy could be just to clearly say no screens once you're in bed."
Brosnan has been developing screenwise.co.nz, an online platform to help parents better manage screen time at home.