A new study showed that children slightly exposed to light before bedtime can prompt the sleep-promoting hormone melatonin to plummet. This can cause sleep disruption long after the light goes out and potential future sleep issues.
Read about the research below:
“[Research] suggests that preschoolers are highly susceptible to the physiological impacts of light at night, and some children may be even more sensitive than others.
‘Our previous work showed that one, fairly high intensity of bright light before bedtime dampens melatonin levels by about 90% in young children,’ said first author Lauren Hartstein, a postdoctoral fellow in the Sleep and Development Lab at CU Boulder. ‘With this study, we were very surprised to find high melatonin suppression across all intensities of light, even dim ones.’
Light is the body’s primary time cue, influencing circadian rhythms that regulate everything from when we feel tired or hungry to what our body temperature is throughout the day.
When light hits the retina, a signal transmits to a part of the brain called the suprachiasmatic nucleus, which coordinates rhythms throughout the body, including nightly production of melatonin. If this exposure happens in the evening as melatonin is naturally increasing, it can slow or halt it, delaying the body’s ability to transition into biological nighttime.
Because children’s eyes have larger pupils and more transparent lenses than adults, light streams into them more freely. (One recent study showed that the transmission of blue light through a 9-year-old’s eye is 1.2-times higher than that of an adult).
‘Kids are not just little adults,’ said senior author Monique LeBourgeois, an associate professor of Integrative Physiology and one of the few researchers in the world to study the circadian biology of young children. ‘This heightened sensitivity to light may make them even more susceptible to dysregulation of sleep and the circadian system. . .’
This does not necessarily mean that parents must throw away the nightlight and keep children in absolute darkness before bedtime. But at a time when half of children use screen media before bed, the research serves as a reminder to all parents to shut off the gadgets and keep light to a minimum to foster good sleep habits in their kids. Notably, a tablet at full brightness held 1 foot from the eyes in a dark room measures as much as 100 lux.
For those children who already have sleep problems?
‘They may be more sensitive to light than other children,’ said LeBourgeois, noting that genes — along with daytime light exposure — can influence light sensitivity. ‘In that case, it’s even more important for parents to pay attention to their child’s evening light exposure.'”
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