Regular exposure to blue light from excessive use of mobile phones and tablets may alter hormone levels and accelerate the onset of puberty, according to a study published at the 60th Annual European Society for Paediatric Endocrinology Meeting.
Exposure for a long time was associated with earlier puberty in female rats. These animals also produced lower melatonin levels and higher levels of reproductive hormones. Researchers already knew that blue light could disrupt sleeping patterns in children and adults, but this new study suggests additional risks due to using mobile phones and tablets during childhood.
Blue lights can disrupt sleep patterns because they disrupt our internal body clock. This exposure in the evening lowers the levels of melatonin which is essential for our bodies to rest and sleep. Melatonin levels are higher during pre-puberty than in puberty, and this drop is believed to play a role in the start of puberty (although puberty is a complex mechanism involving different body systems and hormones).
To assess whether exposure to blue light lowers melatonin levels and therefore triggers puberty earlier, a team of researchers from Ankara, Turkey, used female rats that were exposed to different light cycles: normal light cycle and 6 hours or 12 hours of blue light. The authors detected signs of puberty earlier in the groups exposed to blue light, with the longer duration of exposure causing the earliest onset of puberty.
Female rats exposed to blue light also had lower levels of melatonin, higher levels of estradiol and luteinising hormone (involved in reproduction), and physical changes to the ovarian tissue—all these and consistent with puberty onset. At the 12 hours of exposure, some rats even showed signs of damage and inflammation in the ovaries.
“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. In addition, the longer the exposure, the earlier the onset,” said Dr. Aylin Kilinç Uğurlu. However, “as this a rat study, we can’t be sure that these findings would be replicated in children, but these data suggest that blue light exposure could be considered as a risk factor for earlier puberty onset.”
In practical terms, it’s difficult to mimic exposure to blue light from a small device such as a phone or a tablet in rats, but the time of puberty is roughly equivalent to that of humans (adjusted for life expectancy), and the changes are identical. Despite the study limitations, these findings warrant further investigation of the potential health impacts on children.
“Although not conclusive, we would advise that the use of blue light emitting devices should be minimised in pre-pubertal children, especially in the evening when exposure may have the most hormone-altering effects,” concluded Dr. Uğurlu.