Fear of the dark is common in preschoolers — it’s caused by a surge in cognitive development and imagination at this age. This is why some parents call on a nightlight to help ease their children into dreamland. But take caution about leaving all the lights open. Recent research has found that bright light close to bedtime hinders proper sleep in kids.
Exposed to bright lights an hour before bed, a child’s melatonin levels can be suppressed up to 90 percent, the study results revealed. “And the effects persisted even after the kids returned to dim light,” said lead author Dr. Lameese D. Akacem, an instructor at the University of Colorado and researcher in the Sleep and Development Lab, told The New York Times.
Melatonin is the hormone that regulates and induces sleep. Melatonin levels are typically low during the day and increase at night to prepare for sleep. It’s an important component of every human’s body clock — or how your body knows when it’s time to snooze and when you have to be awake.
“Although the effects of light are well studied in adults, virtually nothing is known about how evening light exposure affects the physiology, health, and development of preschool-aged children,” said Dr. Akacem.
For the study, published in the journal Physiological Reports, researchers observed and tracked the melatonin levels, through saliva samples, of 10 children ages 3 to 5 after being exposed to different sleep environments. First, for five days the kids were asked to follow a sleep schedule to establish a pattern for their body clock.
Then, on the sixth day, the children's homes were made into low-light “caves” where the windows were covered and the light bulbs were swapped for low-wattage ones. With the cave-like environment, the kids were already secreting melatonin almost an hour before their 8:27 PM bedtime.
The next day, researchers exposed the kids to bright light an hour before bedtime by having them play at a light table. “Fifty minutes after the light was gone, most of the children were still not back to 50 percent of the melatonin levels seen the day before,” reported The New York Times.
“Light is our brain clock's primary timekeeper,” senior author Dr. Monique LeBourgeois, an associate professor at the University of Colorado and the director of the sleep and development lab, told Science Daily. “We know younger individuals have larger pupils, and their lenses are more transparent. This heightened sensitivity to light may make them even more susceptible to dysregulation of sleep and the circadian clock.”
Therefore, light, she explained, may make it harder for preschoolers to sleep at night. Moreover, over time, it can even lead to chronic sleep problems at bedtime.
What’s the takeaway? “Parents should avoid having children exposed to very bright light before bedtime,” said Dr. Akacem. If your child is already in bed where the lights are low, try not to have her popping out into the bright light of other parts of the house.
As much as possible, have the parts of the home where your child is likely to come and go at night, like the bathroom and your bedroom, in low-light as well, advised Dr. LeBourgeois. “Just even a short exposure of bright light may suppress melatonin and shut down that sleep-promoting effect.”
The light table used for this study emitted light at levels above handheld screens — it was around the light level of a bright room. Dr. LeBourgeois’ next undertaking is to find out at what level will light start to negatively affect the body clock of a child with a focus on gadgets.
Why not get ahead and start limiting the kids’ screen time before bed already anyway? Past research has shown that it causes poor sleep in kids both in quality and quantity. Read about it here.