Time spent on electronic devices linked to teen sleep problems
30 January 2015
The time spent looking at screens throughout the day and before
going to bed is directly related to poor quality sleep according to
a large study of teenagers published in the online journal BMJ Open.
The study looked at almost 10,000 16 to 19 year olds, all of whom
were part of the Norwegian youth@hordaland study in 2012.
The teens were asked how much screen time they spent outside of
school hours, and on what activities, for any of the following
electronic devices: computer; smartphone; Mp3 player; tablet; games
console; 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
get to sleep (sleep onset latency).
Some gender differences emerged in activities and preferred
devices. Games console use was more popular among the boys, whereas
girls were more likely to use smartphones and Mp3 players. Girls
spent significantly longer on their computers chatting online while
boys spent longer playing games on consoles and computers.
Almost all of the teens said they used one or more electronic
devices shortly (an hour) before going to bed.
Heightened risk of poor sleep
Although frequency of use differed among the various devices, use
of any device during the day and in the hour before bedtime was
linked to a heightened risk of taking longer than 60 minutes to get
In particular, use of a computer, smartphone, or Mp3 player in
the hour before bedtime was significantly associated with taking
longer to fall asleep. A period of more than half an hour is
normally defined as long sleep latency in adults, say the
Total daytime screen use of more than 4 hours was linked to a 49%
greater risk of taking longer than 60 minutes to fall asleep.
And a total of more than 2 hours of screen time after school was
strongly linked to both longer sleep onset latency and shorter sleep
On average, the teens said they needed 8-9 hours of sleep to feel
rested. But those who spent more than 2 hours emailing or chatting
online were more than three times as likely to sleep for less than 5
hours. While those who spent more than 4 hours in front of any
screen were more than 3.5 times as likely to sleep for less than 5
When the analysis looked at individual devices, the strongest
association for shortened sleep and less sleep than deemed necessary
was found for computers, although this technology was one of the
most commonly used of all the electronic platforms.
Multiple devices worse than single
Multi-taskers — those using more than one device — were also more
likely to take longer to get to sleep and to sleep for less — than
those who used only one device.
Teens who used four or more devices were 26% more likely to take
60 or more minutes to fall asleep than those who used just one.
And teens who used two to three devices were 50% more likely to
sleep for less than 5 hours than those who used just one device;
teens who used four or more devices were 75% more likely to do so.
Screen use may simply replace sleeping time or may interfere with
sleep by stimulating the nervous system, suggest the researchers, in
a bid to explain their findings. Alternatively, the light emitted
from electronic devices may interfere with the body clock (circadian
“The recommendations for healthy media use given to parents and
adolescents need updating, and age specific guidelines regarding the
quantity and timing of electronic media use should be developed,”
write the researchers.
“The current recommendation is not to have a TV in the bedroom.
It seems, however, that there may be other electronic devices
exerting the same negative influence on sleep, such as PCs and
mobile phones. The results confirm recommendations for restricting
media use in general,” they conclude.
Hysing M et al. Sleep and use of electronic devices in
adolescence: results from a large population-based study. BMJ Open.
2015;5:e006748. doi 10.1136/bmjopen-2014-006748