Children and adolescents are particularly vulnerable to the sleep-disrupting effects of screen time, as their brains, sleep patterns, and eyes are still developing, according to a new study.
“The vast majority of studies find that kids and teens who consume more screen-based media are more likely to experience sleep disruption,” said first author Dr. Monique LeBourgeois, an associate professor in the Department of Integrative Physiology at the University of Colorado Boulder. “With this paper, we wanted to go one step further by reviewing the studies that also point to the reasons why digital media adversely affects sleep.”
Of more than five dozen studies looking at kids between the ages of five and 17 from around the world, 90 percent found that more screen time is associated with delayed bedtimes, fewer hours of sleep, and poorer sleep quality, the researchers report.
Biological, neurological, and environmental factors all play a role, the scientists note.
Because their eyes are not fully developed, children are more sensitive than adults to the impact of light on the internal body clock.
“Light is our brain clock’s primary timekeeper,” LeBourgeois said, explaining that when light hits the retina in the eye in the evening hours it signals the circadian system to suppress the sleep-promoting hormone melatonin, delaying sleepiness, and pushing back the timing of the body clock.
“We know younger individuals have larger pupils, and their lenses are more transparent, so their exposure and sensitivity to that light is even greater than in older individuals.”
The researchers point to one study that found that when adults and school-age children were exposed to the same amount and intensity of light, the children’s melatonin levels fell twice as much.
Studies have also shown that short-wavelength “blue light” — ubiquitous in hand-held electronics — is particularly potent at suppressing melatonin.
“Through the young eyes of a child, exposure to a bright blue screen in the hours before bedtime is the perfect storm for both sleep and circadian disruption,” LeBourgeois said.
The “psychological stimulation” of digital media — whether it’s exposure to violent media or texting with friends — can also sabotage sleep by boosting cognitive arousal, according to the researchers.
The researchers also note that children and adolescents who leave a phone or computer on overnight in their bedroom are significantly more likely to have trouble sleeping. More than 75 percent of youths have screen-based media in their bedrooms, 60 percent interact with them in the hour before bedtime, and 45 percent use their phones as an alarm.
A recent report from Commonsense Media showed mobile media device use has tripled among young children since 2011, with kids under eight using them 48 minutes a day and many parents incorporating digital media into the bedtime routine.
This summer, LeBourgeois launched a five-year, $2.5 million study funded by the National Institutes of Health, in which her research team goes into the homes of volunteer families, exposes children to varying intensities of light and collects saliva samples to measure changes in melatonin levels and the timing of the biological clock. Ultimately, she believes the study will reveal how little light it takes to impact sleep and circadian rhythms in young children and lead to science-based guidelines for parents and device-makers.
“The preschool years are a very sensitive time of development during which use of digital media is growing more and more pervasive,” she said. “There’s a lot we don’t know.”
LeBourgeois offers these recommendations for parents:
- Limit children’s media use in the hour before bedtime.
- Turn off all electronic media devices at bedtime, and charge them in a central location outside bedrooms.
- Remove all electronic media from your child or teen’s bedroom, including TVs, video games, computers, tablets, and cell phones.
The study was published in the journal Pediatrics.
Source: University of Colorado Boulder