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 “There are probably many possible pathways between screen time and
sleep, some of which are direct,” said lead author Mari Hysing of
Uni Research Health in Bergen, Norway. “The light from the screens
may directly affect our circadian rhythms, and teenagers may be
especially sensitive.”
As reported in the journal BMJ Open, she and her coauthors analyzed
survey responses from almost 10,000 teens, ages 16 to 19, in Western
Norway.
More than 90 percent of girls and 80 percent of boys reported using
a cell phone in the hour before bed, and laptops were almost as
common.
Throughout the day, girls reported an average of 5.5 hours of screen
time with any device - a personal computer, cell phone, MP3 player,
tablet, game console or TV - and boys averaged almost seven hours
per day. A large proportion of those hours were spent chatting
online. Boys and girls spent an average of half an hour each day on
emails.
Boys averaged almost an hour on console video games and more than an
hour on PC games.
Using any device in the hour before bed was associated with a 13 to
52 percent increase in the likelihood of needing more than 60
minutes to fall asleep, the researchers found.
More than four daytime hours of screen time was associated with a
similar increase in risk of “sleep latency,” or taking a long time
to fall asleep.
Screen time was also linked to an increased risk of a sleep deficit
of at least two hours, meaning the kids said they needed two more
hours of sleep than they were actually getting.
The teens tended to use many devices at once, so it was hard to
compare them and see if certain devices were more strongly linked to
sleep quality, Hysing said.
Several studies recently have showed that the more frequently young
people use these media devices, the greater the chance their sleep
will be disturbed, said Michael Gradisar, a clinical psychologist
and sleep researcher at Flinders University in Adelaide, South
Australia.
“This study by Hysing and colleagues was eye-opening because they
showed that screen use above the recommended two hours per day was
associated with sleep durations well below the norm, and in the
range we see linked with poor school performance, emotional
disturbances, and in some cases suicidal ideation,” Gradisar, who
was not part of the new study, told Reuters Health by email.
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“There is now much evidence, including this study, to suggest that
screen time has a direct effect on sleep,” Hysing told Reuters
Health by email.
But, Hysing said, it could also be that “some families who do not
have fixed bedtimes for their teenagers are the same who do not
limit screen time.”
Also, she said. “We know that depressed teenagers often sleep less,
and this might also be related to screen time use.”
This study only included data from one point in time, so there is no
way to prove that using screens caused a change in sleep patterns,
said Emma Adam, a developmental psychologist at Northwestern
University in Chicago.
“We can’t rule out the possibility that they use screens more
because they can’t sleep, but certainly there is other evidence that
screen time right before bed affects sleep,” Adam told Reuters
Health by phone.
The National Sleep Foundation recommends that teens avoid eating,
drinking, or exercising within a few hours of their bedtime and try
to avoid the TV, computer and telephone in the hour before going to
bed.
“While there has been a focus on media use in younger children, we
know that many teenagers do not have parental-set bedtimes nor
restrictions on media use,” Hysing said. “The most important thing
we can do is to keep the night screen free.”
SOURCE: http://bmj.co/1Dups2u
BMJ Open, online February 2, 2015.
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