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  • Researchers are trying to understand why some children are going through puberty at an earlier age
  • One theory is that blue light from devices may affect melatonin that could increase the risk of early-onset puberty.
  • A new rodent study looked at that possiblity, but experts say more research is needed.

Researchers are trying to figure out if exposure to blue light emitted by electronic screens could increase children’s risk of early onset puberty, and might even damage their future fertility.

Now new research presented at the 60th Annual European Society for Paediatric Endocrinology meeting found that rats exposed to blue light underwent puberty earlier.

Dr. Rebecca Fisk, a pediatric hospitalist at Lenox Hill Hospital in New York, told Healthline, that blue light is a part of the visible light spectrum that is emitted by the sun.

“Which in fact is where we get most of our blue light exposure,” she continued.

According to Fisk, artificial sources of blue light include LED and fluorescent lights, and electronic devices like smartphones, televisions, e-readers, video game consoles, computers, and tablets.

Researchers say they are investigating if there is a link between blue light exposure and reduced melatonin levels. And looking for evidence if increased screen time for children may play a role in this increase.

According to the study authors, melatonin levels are higher during pre-puberty than in puberty. As a result, high levels of melatonin may be a factor in delaying the start of puberty.

Researchers observed 18 female rats to investigate the effects of blue light exposure on reproductive hormone levels and the time of puberty onset.

The animals were separated into three groups; one exposed to a normal light cycle, while two were exposed to 6 or 12 hours of blue light each day.

In both groups exposed to blue light, puberty occurred significantly earlier than expected. The rats exposed to blue light longest were most affected.

Rats with 12 hours of exposure to blue light also showed signs of cell damage and inflammation in their ovaries. The animals were also found to have lower melatonin levels.

“We have found that blue light exposure, sufficient to alter melatonin levels, is also able to alter reproductive hormone levels and cause earlier puberty onset in our rat model,” study author Dr. Aylin Kilinç Uğurlu said in a statement.

Fisk explained that melatonin is a hormone produced by the brain in response to darkness.

“It is made mainly in the pineal gland; a small amount is made in the retina,” she said. “It aids with the timing of one’s circadian rhythms, our 24-hour internal clock, and also with sleep.”

She emphasized that exposure to light at night can block melatonin production.

“Any type of light can suppress melatonin secretion,” noted Fisk.

More study is needed to determine if these effects seen in rats would be applicable to humans.

“It is possible that disrupted melatonin, or perhaps more generally, disrupted sleep and sleep stages from blue light, can have an impact on child development,” confirmed Dr. Alex Dimitriu, double board-certified in Psychiatry and Sleep Medicine and founder of Menlo Park Psychiatry & Sleep Medicine and BrainfoodMD.

He added that the limitation of this study is how well these effects would generalize from rats to humans, which he pointed out, is “not always the case.”

“Whether melatonin is the common pathway is to be seen,” he said. “However it is without a doubt that blue screens impair sleep – both in quality and in quantity.”

Dimitriu noted that since this study observed rats, there is no certainty that these findings would be duplicated in children.

“In addition, this study involved a tiny sample of six rats per group,” he said. “In my opinion, this is far too small a sample size to be able to draw conclusions.”

“Not to mention that the reader is being asked to extrapolate data in a tiny sample of rats to effects in human beings, specifically children,” he continued.

Dimitriu said that although findings in this study are inconclusive, use of devices that emit blue light in the evening should be minimized for both pre-pubertal and pubescent children until more studies with larger sample sizes can address these issues.

“And determine if there is a causal relationship or if blue light exposure is a risk factor in pubertal onset occurring earlier,” he said.

Fisk said that the effects of early puberty in girls can be linked to a greater risk for certain health issues including breast cancer, teen pregnancy, HPV, heart disease, and diabetes.

“Early puberty, in both boys and girls, has also been connected to a higher risk of mental health issues such as anxiety and depression, eating disorders, and conduct disorders,” she said.

Fisk explained that early puberty can be slowed down through exercise, better nutrition (like less processed foods and fast foods), and awareness of hormones in food.

According to Dimitriu, limiting screen time, especially before bed, is good advice for everyone regardless if it is linked to the risk of early-onset puberty.

“Both adults and children will at minimum experience some drop in melatonin levels and some lightening of the quality of sleep following blue light exposure before bedtime,” he said.

For good sleep, Dimitriu said he advises his adult patients to turn “tech off at ten.”

“That would hold for kids, possibly closer to 7,” he added. “So there is some screen-free downtime before sleep.”

New research used an animal model to find that blue light exposure may increase the risk of early onset puberty in children.

Experts say more study needs to be done to verify that these findings would hold in a human population.