Numerous studies have demonstrated that too much screen time before bed can keep kids up at night. New research from Brown University adds another layer of understanding to the relationship between light and sleep in children and teens. The study finds that young tweens and teens in the early stages of puberty are strongly affected by nighttime light, much more than older teens in late or post-puberty. The findings indicate that parents should limit young teens’ exposure to light before bedtime.
The researchers examined the sleep biology of boys and girls aged 9 to 16 in lab experiments. To determine the impact of light on sleep, the researchers exposed the children to various levels of light and then measured their melatonin—a hormone associated with sleep timing. The 38 children in early or middle puberty and 29 teenagers in late or post-puberty were exposed to an hour of light at 15 lux (dim light), 150 lux (normal room brightness) and 500 lux (bright like a supermarket).
An hour of nighttime light exposure significantly reduced melatonin production for children in early puberty and moderately reduced melatonin production for older teenagers. For children in early puberty, 15 lux of light suppressed melatonin by 9.2 percent, 150 lux suppressed melatonin by 26 percent, and 500 lux suppressed melatonin by 36.9 percent. For older teens, 15 lux of light had no effect on melatonin production. 150 lux and 500 lux reduced melatonin production by 12.5 percent and 23.9 percent, respectively. There was no difference in melatonin production between boys and girls.
“Small amounts of light at night, such as light from screens, can be enough to affect sleep patterns. Students who have tablets or TVs or computers—even an ‘old-school’ flashlight under the covers to read—are pushing their circadian clocks to a later timing. This makes it harder to go to sleep and wake up at times early the next morning for school,” stated senior study author Mary Carskadon, professor of psychiatry and human behavior at Brown University and director of chronobiology and sleep research at the E.P. Bradley Hospital.
This research is published in the Journal of Clinical Endocrinology & Metabolism.
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