Study suggests bright lights inhibit the production of melatonin in preschoolers

Mar 6 2018

A new study has revealed that an hour exposure to bright light inhibits the production of sleep-promoting hormone melatonin in preschoolers and maintains suppression for a minimum of 50 minutes after lights are switched off.

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The study is increasingly prominent given that the use of electronics amongst preschoolersis growing exponentially. It comes after a growing body of evidence suggesting that structural differences in the eyes of young children make them more vulnerable to impact of light on sleep and the body clock.

Lameese Akacem, the study’s lead author and a CU Boulder instructor and researcher in the Sleep and Development Lab, said that although the consequences of light in adults are well-studied, knowledge about how the exposure of light affects the health, physiology, and development of preschoolers is severely lacking.

The research involved the study of 10 healthy children between 3 to 5 years old over a seven day period. During days 1 to 5, the children followed a strict bedtime schedule to adjust their body clocks and establish a pattern in which their melatonin levels started to rise at about the same time each evening.

On the sixth day, the scientists visited the children’s homes and provided them with a dim-light environment. This was achieved by covering windows with black plastic and replacing existing lights with low-wattage light bulbs.

This ensured that all children were exposed to the same amount of light, allowing melatonin levels to be measured accurately.

The sixth day afternoon, the researchers took repeated samples of saliva to evaluate melatonin levels at different times. The following evening, after the children completed their day playfully that is referred to as “the cave,” they were asked to play or color with magnetic tiles on the surface of a light table that emits 1,000 lux of light (the brightness of light in a bright room) for an hour.

Then, the samples were taken again by the scientists, relating them to those samples that were taken the night before.

The levels of melatonin were 88% lower after the exposure of bright light. Levels were inhibited at least for 50 minutes after lights off.

When light reaches the retina in the eye during evening, it creates a cascade of signals to the circadian system to inhibit melatonin and push back the entrance of the body into its "biological night." For preschool-aged children, this may not only lead to have sleeping issues, but to persistent problems feeling sleepy at night, said LeBourgeois.

Melatonin also plays an important role in regulating blood pressure, glucose metabolism, and temperature.

The sample size used in the current study was 1,000 lux, which is significantly greater than the intensity of a basic handheld electronic device, she added.

The researchers stress that the comparisons between the current study and studies in adults must be considered with caution as they come with different research protocols.

The preschool years are a very sensitive time of development during which use of digital media is growing more and more pervasive. Use of electronic media among young children has tripled since 2011. We hope this research can help parents and clinicians make informed decisions on children's light exposure.”

Monique LeBourgeois, Senior Author

The scientists will now work to further explore the effects of bright light on circadian rhythms. The next study will involve exposing 90 children to different intensities of light.

Source:

https://www.eurekalert.org/pub_releases/2018-03/uoca-pet030518.php