Scientists found how bright light keeps preschoolers wired at night

The sensitivity of the circadian system to evening bright light.


According to a new study, presenting preschoolers to an hour of brilliant light before sleep time totally close down their production of the sleep-promoting hormone melatonin and keeps it smothered for no less than 50 minutes after lights out. The investigation is the first to survey the hormonal effect evening light introduction can have on youthful kids. It comes when utilization of hardware is quickly extending among this age gathering and adds to a developing assortment of proof proposing that—on account of basic contrasts in their eyes—kids might be more helpless against the effect light has on rest and the body clock.

Lead author Lameese Akacem, a CU Boulder instructor said, “Although the effects of light are well studied in adults, virtually nothing is known about how evening light exposure affects the physiology, health, and development of preschool-aged children. In this study, we found that these kids were extremely sensitive to light.”

For the study, scientists enrolled 10 healthy children ages 3 to 5 years in a seven-day protocol. For the 5 days, the children followed a strict bedtime schedule to normalize their body clocks. They thus settled into a pattern in which their melatonin levels began to go up at about the same time each evening.

On day six, Akacem’s group came into the kids’ homes and made a diminish light condition, covering windows with dark plastic and swapping out existing lights with low-wattage knobs. This guaranteed every one of the kids was presented with a similar measure of light—which can impact melatonin timing and levels—before tests were taken.

That evening, the scientists took intermittent salivation tests to survey melatonin levels at different circumstances. The next night, subsequent to spending the day in what they energetically alluded to as “the give in,” the youngsters were welcome to shading or play with attractive tiles over a light table radiating 1,000 lux of light (about the shine of a splendid room) for 60 minutes.

At that point the analysts took tests once more, contrasting them with those taken the prior night. They found that the melatonin levels were 88 percent bring down after brilliant light introduction. Levels stayed stifled no less than 50 minutes after the light was stopped.

Coordinate examinations of this investigation and concentrates in grown-ups must be made with an alert in light of varying exploration conventions, the analysts stretch. Notwithstanding, they take note of that in one examination, a one-hour light boost of 10,000 lux (10 times that of the present investigation) stifled melatonin by just 39 percent in grown-ups.

Senior author Monique LeBourgeois said, “Light is our brain clock’s primary timekeeper. We know younger individuals have larger pupils, and their lenses are more transparent. This heightened sensitivity to light may make them even more susceptible to dysregulation of sleep and the circadian clock.”

“When light hits the retina in the eye in the evening, it produces a cascade of signals to the circadian system to suppress melatonin and push back the body’s entrance into its “biological night.” For preschoolers, this may not only lead to trouble falling asleep one night, but to chronic problems feeling sleepy at bedtime.”

The study sample size was small and it used only one intensity of light, 1,000 lux, which is far greater than the intensity of a typical handheld electronic device, she notes.

With a new $2.4 million grant from the National Institutes of Health, LeBourgeois recently launched a study in which she will expose 90 children to light of different intensities to determine how much it takes to impact the circadian clock.

LeBourgeois said, “The preschool years are a very sensitive time of development during which use of digital media is growing more and more pervasive. We hope this research can help parents and clinicians make informed decisions on children’s light exposure.”

The research is published today in the journal Physiological Reports.