Thanks in part to the ubiquity of handheld screens in modern society, sleep researchers are beginning to discover significant links between light, both natural and unnatural, and sleep. A 2014 study found that even small amounts of nighttime use of “portable light-emitting devices” like smartphones and tablets can significantly reduce individuals’ ability to fall and stay asleep. A more recent 2017 publication in the journal Pediatrics found that this nighttime screen time affects kids far worse than adults, yet the mechanisms behind that increased sensitivity remained unknown. Just this week, however, a new study published in the journal Physiological Reports claims to have found the link between light and kids’ sleep, suggesting that more darkness may be the key to helping children get the sleep they need.

This new study examined melatonin levels in 10 children, ages 3 to 5. Baseline measurements were taken over five days as they went about their normal sleep routines. The children then spent a whole day in dim light conditions, the night after which they spent an hour playing with a bright touchscreen before bed. Children’s melatonin levels were found to drop by 90% after this light exposure, and had only recovered to 50% an hour after their exposure. This is the first time such a direct link between melatonin and light exposure has been observed in a clinical setting.

The authors write that the discovery of this link could possibly open the doors to new means of combating childhood sleep issues:

To our knowledge, this study is the first to quantify the melatonin suppression response to evening light exposure in healthy 3‐ to 5‐year‐old children. In this well‐controlled innovative study, we found a robust and sustained response of the circadian system of young children to evening bright light exposure. Together, these data and our approach represent a first step in understanding the dynamics of the circadian response to light in early childhood and suggest that evening light exposure may increase risk for evening sleep disturbances in preschool‐age children.

While the authors of this study aren’t yet making recommendations, this is yet one more reminder to put the phones and tablets away as the sun goes down. Once kids are asleep, parents can also darken their homes to prevent kids from being exposed to light if they should wake up in the night.

Brett Tingley

Brett Tingley is a writer and musician from the mountains of Western North Carolina. Contact him at [email protected]

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