New Study Shows How Screen Time Affects Kids’ Sleep

Researchers found that even minimal exposure to light before bed interfered with kids’ sleep. Here are 5 tips for keeping their circadian rhythms in check.

A young girl sits in front of a large window with a cityscape in the background. She is concentrated on tablet that emits blue light. A new study shows that light exposure before bed -- especially blue light -- negatively impacts children's sleep more than previously thought.
CMB / Getty Images

Parents know that bedtime can be a struggle — often an epic battle. All we want at the end of our long days is to relax with a favorite book or TV show, but sometimes our little munchkins decide that 7 p.m. is the perfect time to start bouncing off the walls.

We’ve all been there, and that’s why we try our best to ensure that nothing interferes with bedtime. According to a new study, though, there might be something that’s having a bigger impact on our kids’ sleep than we might realize: light exposure.

That’s right — researchers from the University of Colorado Boulder found that even minimal exposure to light before bed interfered with kids’ sleep. This can include screen time, but also any type of light in the room.

Let’s take a look at what this study means for parents, and what we can do to minimize the impact.

How light exposure affects our ability to catch Zzz’s

All of us are sensitive to light at bedtime, says Dr. Funke Afolabi-Brown, a triple board-certified sleep medicine physician and founder of Restful Sleep. “Light is the strongest cue for our circadian rhythm (internal clock),” she explains. “At night time, our brains produce a hormone called melatonin, inducing sleepiness.”

The more light we’re exposed to in the hours before bedtime, the less melatonin we produce, which makes it more difficult to fall asleep. You may have noticed this in your own life at times, says Dr. Chris Winter, neurologist, sleep specialist, Sleep Advisor, and author ofThe Rested Child.”

“Anybody who has frequent power outages or who spends a lot of time in the dark or in the woods will tell you, it’s really healthy for sleep,” he says. “When you really control light and make it go away, it’s amazing how positive an impact it has.”

What the study found

Although all of us are impacted by light exposure at bedtime, this new study, published in the Journal of Pineal Research, found that children are particularly sensitive to this phenomenon.

Researchers studied 36 preschool-aged children over the course of nine days, tracking both light exposure and the kids’ melatonin levels. Eight days in, the researchers turned the kids’ homes into what they described as “caves,” making the light as low as possible, and putting black tape on their windows.

The following day was the opposite: The kids were set up with a light table (to mimic the experience of looking at a glowing screen). Not all of the light tables had the same intensity. Some were as low as 5 lux while others were as high as 5,000 lux.

Researchers found that melatonin levels decreased a whopping 70 to 99% on the night that kids used the light table. There was little difference between the kids who were exposed to less intense light versus kids who were exposed to more intense light.

“Together, our findings indicate that in preschool-aged children, exposure to light before bedtime, even at low intensities, results in robust and sustained melatonin suppression,” Lauren Hartstein, one of the study researchers said in a press release.

Why children are more sensitive to light exposure

According to Afolabi-Brown, there are physiological reasons why kids are more sensitive to light exposure than adults.

“Children, particularly preschoolers, are more sensitive to light at bedtime because they have larger pupils than older children and adults,” she explains. “This means the light hitting the back of their eye has a greater impact on the suppression of melatonin.”

5 tips for decreasing light exposure before bed

Let’s be honest: Many parents rely on screen time in the evenings, and the idea of turning our homes into caves every night sounds completely impractical. But there’s no need to fret. Winter says there are few things parents can do to keep our kids’ natural circadian rhythms in check.

Save screen time for the morning
While it’s important to limit screen time in the evenings, exposing your kids to light in the morning is just fine, and even helpful for regulating their circadian clocks, Winter says. If your child is unhappy about nighttime limits, Winter suggests letting them go all-out in the morning.

Use low-intensity lights
Dimming lights is important, but so is the type of light you are using. Winter notes that purchasing lights that don’t have a lot of blue-green wavelength is a smart idea. This may mean decreasing the use of fluorescent light bulbs and certain LED lights at night. Instead, consider warmer gold-hued lights or dim red lights, both of which produce less blue light.

Change your family’s screen time routines
To stick to a screen-free evening plan, you need to create routines that limit screen time at night, making especially sure that no one brings their phone or iPad into their bedroom.

Winter’s family does just that. “If you look in our kitchen at night, there’s five phones in this little cubby,” he shares. “Everybody’s got their own charging cord, all right there. You can access your phone whenever you want; you just have to come downstairs and check your messages.” Fill the time you might otherwise be watching TV with analog activities like board games and books.

Model screen time limits
Let’s face it: Parents are just as guilty of indulging in screen time at night as our kids are. “I think it’s important for parents to model it,” says Winter. “So if you can have a rule that nobody has their phones in their bedrooms, that includes the parents.”

Try blue light glasses
Blue light in particular can disrupt circadian rhythms. Winter suggests blue-light-filtering glasses — and kids can use them too! “A lot of kids have them on their bedside tables,” he says. “When it’s time to go to bed, they just put their little blue-blocker glasses on, and that way the light of the computer’s not affecting them as much.”

Some of these things are easier said than done, for sure, and it’s a bummer to find out that kids are even more sensitive to light exposure than we might have realized. But parents aren’t powerless here. Just a few tweaks to our kids’ bedtime routines can make a difference. And we parents deserve at least a few quiet hours to ourselves each night, don’t we?