Researchers found that a nine-year-old who watched
five hours of television a day, for example, slept an average one
hour less a night than a nine-year-old who watched television for
less than an hour and a half a day, lead author Marcella Marinelli,
from the Center for Research in Environmental Epidemiology in
Barcelona, told Reuters Health.
The study team followed some 1,700 children for up to three years
and found those who increased their TV time got even less sleep as
they grew up.
"This study really demonstrated that kids who watch a lot of
television and continued to do so continued to have a trajectory of
less sleep than they should have," said Christina Calamaro, from the
Nemours Alfred I. duPont Hospital for Children in Delaware, who was
not involved in the research.
Marinelli and her colleagues write in JAMA Pediatrics that theirs is
the first study to examine the relationship over years between the
amount of time toddlers and school-age children spend watching
television and the amount they spend sleeping.
The American Academy of Pediatrics estimates the average child
spends eight hours a day in front of a screen. AAP recommends that
parents limit kids' daily screen time to one or two hours.
Pre-school age children need a total of 11 to 12 hours of sleep a
day and school-aged kids need at least 10 hours a day, according to
the National Institutes of Health.
Using data from a larger health study, Marinelli's team assessed the
sleep and television habits of 1,713 children in two Spanish cities
and on the Mediterranean island of Menorca.
In the cities of Sabadell and Valencia, researchers asked parents
how much time their children slept and how much TV they watched when
they were two years old and again when they were four years old. In
Menorca, researchers questioned the parents of children when they
were six years old and again at nine years old.
The researchers categorized children who watched less than an hour
and a half a day of television as "shorter" TV viewers and those who
watched more than that as "longer" viewers.
TV viewing times at the beginning of the study period ranged from
zero to a maximum of eight hours a day, though the median viewing
time was about one hour a day. Sleep times ranged from three to 20
hours a day initially, but the median was about 12 hours for
two-year-olds, 10 hours for four-year-olds and 11 hours for the
At all points, kids who were longer viewers got less sleep than kids
who were shorter viewers.
Median sleep times dropped by about two hours during the
two-to-three year follow-up period for all age groups. But kids who
increased their TV viewing during that period lost even more sleep
time than the others — an average of 20 percent.
Children who reduced their viewing time during follow-up tended to
get more sleep, but that result could have been due to chance, the
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Marinelli's team did not look at what kinds of shows the children
watched on television, what times of day they watched or where the
TVs were located. Their study cannot prove that TV viewing caused
the differences seen in sleep times or explain why that might be.
One recent study found slightly older kids, aged 11 to 13, slept
significantly less when they frequently watched television before
hitting the sack (see Reuters Health story of January 24, 2014 here:
The researchers adjusted their findings for other factors that might
influence the results — including the kids' gender, weight,
exercise, symptoms of attention-deficit hyperactivity disorder,
whether children slept alone or with others, humidity in their
bedrooms and the age of their mattresses. Researchers also adjusted
for parents' marital status, educational level and
"They controlled for all the right variables, and television popped
out," Calamaro said.
"We are not paying attention to how much technology children are
using and how much television children are watching and what it's
doing to their sleep."
Calamaro agreed with the study authors, who theorized that
fast-paced television images could disrupt children's brain
development or might cut children's motivation to play, exercise,
draw and do other things that enhance neurodevelopment. She said
television time could also simply displace sleep time.
Calamaro stressed the importance of playtime and sleep to children's
"This paper really says, wait a minute, when television viewing
starts young, it continues to be an issue for children's sleep as
they get older. It feeds into parents' need to limit technology at
an early age," she said.
Marinelli said she only allows her three-year-old daughter to watch
educational television and limits her to no more than half an hour a
"Parents must control the use of television especially in very young
children and also the use of other devices, for example mobile
phones," she said.
JAMA Pediatrics, online March 10, 2014.
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