Teenagers who spend more time watching TV, using iPads and playing electronic games take longer to fall asleep and get poorer quality rest. A new study suggests the growth in use of electronic media devices by children could harm their physical and mental health.
The 16-19-year-olds were asked how much screen time they spent outside school hours, and on what activities, for any of six electronic devices: computer, tablet, smartphone, MP3 player, games console（游戏机）and TV. They were also asked questions about their sleep routine on weekdays and at weekends: when they normally went to bed and got up; how much sleep they needed to feel rested; and how long it took them to get to sleep. Girls spent longer on their computers chatting online while boys spent longer playing games on computers.
The study found poorer quality sleep was related to more time spent on such devices, and it often took more than an hour todrop off. Total daytime screen use of more than four hours was related to a 49 percent greater risk of taking longer than 60 minutes to fall asleep.
On average, the teens said they needed 8-9 hours of sleep to feel rested. But those who spent more than two hours emailing or chatting online were more than three times as likely to sleep for less than five hours. Those spending more than four hours in front of any screen were 3.5 times as likely to sleep for less than five hours. Computers were the device most likely to cause problems.
Dr Mari Hysing, of Uni Research Health, Bergen, said screen use may simply replace sleeping time or it may affect sleep by stimulating the nervous system. It is also possible that the light from electronic devices may affect a teenager's body clock. "The recommendation is not to have a TV in the bedroom," added Dr Mari Hysing.
