We know it: it is not recommended to watch television, use your phone or tablet before sleeping because their blue light disturbs sleep. According to an American study, any exposure to light before bedtime can reduce levels of melatonin, the sleep hormone, in children.
- Exposure to light decreased melatonin levels in children by 69.4-98.7% compared to the previous night.
- About an hour after turning off the light, melatonin levels did not rise in most children.
The night light keeps away the monsters that hide under the children’s bed and fight against their fear of the dark. Problem: That super-dim lamp turned on at night could impact toddler sleep. This was revealed by American scientists in a study published in the journal Journal of Pineal Research January 8. They reported that any type of exposure, however small, to light, such as candlelight, could keep children awake.
“In adults, light during the evening suppresses melatonin in a non-linear manner as a function of intensity. In children, low-intensity light before bedtime has a robust melatonin suppressing effect (i.e. the sleep hormone)”, wrote the authors in the research.
An analysis of melatonin levels in children
Before drawing this conclusion, the researchers conducted their work with 36 children, aged 3 to 5, in good health for 9 days. During the study, the toddlers wore a wrist-mounted device that tracked their sleep and light exposure. For the first seven days, the children had to sleep at fixed times in order to set their biological clocks and have their melatonin levels rise each evening at around the same time.
On the eighth day, the team transformed the children’s room into a “cave”. She placed black plastic on all the windows so that the light would be dimmed. The scientists took saliva samples from the toddlers every half hour, from early afternoon until bedtime, to determine when their melatonin levels spiked. On the last day, the children played games on a light table an hour before bedtime. The light intensity varied from “5 to 5,000 lux”.
Decreased melatonin levels in children due to light exposure
According to the results, exposure to light reduced melatonin levels by 69.4 to 98.7 percent compared to the previous night. According to the scientists, even in response to light ranging in intensity from 5 to 40 lux (which is much dimmer than typical room light), melatonin dropped by an average of 78%. “We also found that melatonin levels remained below 50% for at least 50 minutes after the light was turned off for the majority (62%) of participants,” the researchers said.
“We were very surprised to see a high suppression of melatonin for all light intensities, even low,” said Lauren Hartstein, lead author of the study in a statement. The team concluded that preschoolers were very sensitive to light exposure before bedtime. She recommended that parents reduce the latter to promote good sleep habits in children.
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