girl uses a tablet at night

Bright screens keep kids awake on school nights

Light from tablets or phones in the hour before bed can significantly disrupt sleep time for kids, particularly those between the ages of 9 and 15.

Enough light exposure at night can keep anyone from falling asleep as quickly as they otherwise would have. But a new study finds the sleep biology of boys and girls in the earlier stages of puberty are especially sensitive to light at night compared to older teens.

In lab experiments, an hour of night-time light exposure suppressed their production of the sleep-timing hormone melatonin significantly more than the same light exposure did for teens aged 11 to 16 who were farther into puberty.

Later and later

The brighter the light in the experiments, the more melatonin was suppressed. Among 38 children in early to middle puberty an hour of 15 lux of light (think dim “mood” lighting) suppressed melatonin by 9.2 percent, 150 lux (normal room light) reduced it by 26 percent, and 500 lux (as bright as in a supermarket) reduced it by 36.9 percent.

The 29 teens in the late or post-puberty stage were also affected, but not as much. Exposure to 15 lux did not suppress melatonin at all, 150 lux reduced it 12.5 percent, and 500 lux reduced it by 23.9 percent.

The effects were the same for boys and girls.

[Grades and moods suffer for teen night owls]

“Small amounts of light at night, such as light from screens, can be enough to affect sleep patterns,” says study senior author Mary Carskadon, professor of psychiatry and human behavior at Brown University.

“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.”

Researchers say children and their parents should limit use of screens at bedtime, even though it has become pervasive. One study found that 96 percent of teens use at least one form of technology in the hour before going to bed.

Other researchers from Brown, Monash University, and Rush University Medical Center are coauthors of the study. The National Institute of Mental Health and the National Heart Lung and Blood Institute supported the work that was published in the Journal of Clinical Endocrinology & Metabolism.

Source: Brown University