Megan Brooks

June 22, 2016

DENVER — In very young children, exposure to bright light in the evening suppresses melatonin, which has implications for use of electronic devices before bed, new research shows.

Light-induced suppression of melatonin, which controls the sleep–wake cycle, has been studied in adolescents and adults, but studies in early childhood are lacking.

Lameese Akacem, MS, graduate student in the Sleep and Development Laboratory at the University of Colorado Boulder, and colleagues quantified the magnitude of melatonin suppression in response to evening bright-light exposure in 10 preschool-age boys and girls.

Akacem reported here at SLEEP 2016: 30th Anniversary Meeting of the Associated Professional Sleep Societies.

Lasting Effect

The children participated in a 7-day protocol. On days 1 to 5, they followed a stable sleep schedule, verified with actigraphy. On day 6, the children entered a dim-light environment (<10 lux in the angle of gaze) for 1 hour before providing saliva samples every 20 to 30 minutes from the afternoon until 50 minutes after scheduled bedtime (baseline condition).

On day 7, the children remained in dim-light conditions until 1 hour before bedtime, after which they were exposed to a bright-light stimulus for 1 hour (1033.8 lux; light condition) and then reentered dim-light conditions. Saliva samples were obtained before, during, and after bright-light exposure and were time-anchored to baseline samples.

"One hour of evening bright-light exposure suppressed children's melatonin secretion by roughly 90%," Akacem noted in her presentation. "Melatonin levels remained suppressed for up to 50 minutes after termination of the light stimulus. After the light exposure, melatonin levels did not return to 50% of those observed in the dim-light condition for 7 of the 10 children," she reported.

These findings, Akacem concluded, show that young children are sensitive to the melatonin suppression effects of light in the evening, which persisted after the end of bright-light exposure.

Akacem said further studies are needed to investigate the effect of light-induced melatonin suppression on sleep timing and bedtime resistance in young children, and to examine melatonin suppression in response to evening use of electronic devices.

Poor Pacifiers

Commenting on the study for Medscape Medical News, Saul Rothenberg, PhD, from the Sleep Center at Greenwich Hospital, Connecticut, said the study underlines the role of light exposure and sleep quality.

"Parental instincts to read to their children before bed is good because it's not exposing the kids to extra light at bedtime and minimizes time on devices. I think the lion's share of why kids have difficulty sleeping is related to the home environment. The light exposure issue gets more important as kids get older and become teenagers," said Dr Rothenberg.

"To me, the importance of the study is to say biological clocks are there and they are important, even when you're young, and you don't want to do anything that overtly or directly pushes them in the wrong direction. This message may be especially important for younger parents or parents with lower coping skills who resort to electronic devices to pacify their kids. That's clearly not helpful," he added.

The study was supported by the University of Colorado Boulder. The authors have disclosed no relevant financial relationships.

SLEEP 2016: 30th Anniversary Meeting of the Associated Professional Sleep Societies: Abstract 0130. Presented June 12, 2016.

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