New research offers a compelling reason for parents to ban
smartphones, tablets and laptops in their children's bedrooms at night:
The bright light of these devices may lower levels of melatonin, a
hormone that prompts sleep.The effect was most pronounced for kids just
entering puberty, with nighttime melatonin levels suppressed by up to 37
percent in some cases, the investigators found.With a recent study
suggesting that 96 percent of teens use at least one high-tech device in
the hour before bedtime, the researchers have a suggestion for parents.
"The
message is that we really have to be careful about protecting our
especially young teens from light at night, which means parents need to
get all screens out of the bedroom, because ultimately they can be quite
damaging to a child's capacity to get enough sleep," said study
co-author Mary Carskadon. She is a professor of psychiatry and human
behavior at Brown University's Alpert Medical School, in Providence,
R.I.Puberty and changing sleep habits go hand-in-hand, the study authors
noted, as growing kids start to push for later bedtimes.To some degree,
the shift is likely prompted by several social factors, including the
loosening of parental restrictions, budding friendships and media. But
scientists believe that biological factors also play a role, as a
child's internal sleep clock starts to changAt the heart of that change
is light sensitivity, said Carskadon, who's also director of the Sleep
and Chronobiology Research Laboratory at the E.P. Bradley Hospital. Her
team theorized that puberty increases a child's sensitivity to light at
night, causing melatonin levels to stay low and delay sleep.
But
the researchers also suspected this natural process could be knocked
out of whack when newly light-sensitive children are around the bright
glare of modern technology.So the study authors focused on 38 children
between the ages of 9 and 15 (early puberty), along with 29 boys and
girls between the ages of 11 and 16 (later or post-puberty).For four
nights, all were exposed to a single hour of light, involving four
different brightness levels. Brightness levels ranged from near-dark
"romantic restaurant lighting" all the way up to what Carskadon called
"light you would find in the produce section of your favorite large
supermarket."The exposures occurred either at 11 p.m. or 3 a.m., the
authors said.The result: While melatonin readings were uniform during
the early morning light tests, late-night light tests caused much
greater melatonin suppression among boys and girls at the earliest
stages of puberty.
In that group, dim "mood" lighting suppressed
melatonin by more than 9 percent, while "normal" room light triggered a
26 percent dip and "bright" light prompted a 37 percent plunge. Overall,
older teens saw much smaller drops in melatonin levels, the study
found.The study did not prove that bright light before bedtime causes
adolescents to get less sleep, however."We cannot say we found a sleep
'disturbance,'" Carskadon said. "But what we did find was that young
children exposed to light at bedtime saw their melatonin production
suppressed. And this could cause sleep rhythms to be affected in a way
that causes children to stay up later, which is exactly what adolescents
need not to be doing."Dr. Jim Pagel, director of Rocky Mountain Sleep
in Pueblo, Col., agreed with the finding."It doesn't surprise me," he
said. "At puberty onset, the circadian pattern is very unstable and very
sensitive to light. So the problems they're finding make sense."
That
opinion was seconded by Kelly Baron, director of the Behavioral Sleep
Medicine Program at Northwestern University's Feinberg School of
Medicine in Chicago."This study didn't actually test how light affected
sleep itself, but it did find that it causes a problem on the pathway to
sleep by suppressing melatonin," Baron said."At the same time, other
studies have consistently shown that electronics in the bedroom are
detrimental to sleep for both parents and kids, frankly, which means we
all really should be thinking about ways to limit our exposure to
electronics, and light in general, before we go to bed," Baron said.
The study findings were published online recently in the Journal of Clinical Endocrinology & Metabolism.
- Health24
Light from smartphones and tablets affects melatonin levels
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