Exposure to blue light, through regular tablet and smartphone use, can alter hormone levels and increase the risk of earlier puberty, according to data from a rat study presented at the Society's 60th Annual Meeting. European Pediatric Endocrinology.
The longer duration of blue light exposure was associated with an earlier onset of puberty in the female rats, who also showed reduced levels of melatonin, increased levels of some reproductive hormones, and physical changes in their ovaries.
The use of mobile devices that emit blue light has previously been linked to disturbed sleep patterns in children, but these results suggest there may be additional risks to child development and future fertility.
The increasing use of blue light-emitting devices, such as tablets and smartphones, has previously been linked to reduced sleep quality in both children and adults. This is thought to be due to the disruption of our body clock, as blue light inhibits the nightly rise in levels of the hormone melatonin, which prepares our bodies for rest and sleep.
Melatonin levels are generally higher during prepuberty than puberty, which is thought to contribute to delaying the onset of puberty. Puberty is a complex process that involves the coordination of various body systems and hormones.
In recent years, several studies have reported the increase in early onset of puberty in girls, especially during the Covid-19 pandemic. The relationship between blue light exposure and reduced melatonin levels suggests that increased screen time, such as during pandemic restrictions, may be playing a role in this reported increase. However, it is very difficult to assess this in children.
LESS MELATONIN, MORE REPRODUCTIVE HORMONES
In this study, Dr. Aylin Kilinç Ugurlu and her colleagues from Ankara, Turkey, used a rat model to investigate the effects of blue light exposure on reproductive hormone levels and the timing of puberty onset. The female rats were divided into three groups of six and exposed to a normal light cycle, 6 hours or 12 hours of blue light.
The first signs of puberty occurred significantly earlier in both groups exposed to blue light, and the longer the duration of exposure, the earlier the onset of puberty.
The rats exposed to blue light also had reduced levels of melatonin and increased levels of specific reproductive hormones (estradiol and luteinizing hormone), as well as physical changes in their ovarian tissue, all consistent with the onset of puberty. At 12 hours of exposure, the rats also showed some signs of cell damage and inflammation in their ovaries.
Dr. Aylin Kilinç Ugurlu points out that they have discovered that exposure to blue light, sufficient to alter melatonin levels, "is also capable of altering the levels of reproductive hormones and causing an earlier onset of puberty in our rat model Also, the longer the exposure, the earlier the onset," he warns.
In addition, he warns that, "since this is a study with rats, we cannot be sure that these results are reproduced in children, but these data suggest that exposure to blue light could be considered a risk factor for the onset more early puberty.
He points out that it is difficult to mimic blue light exposure equivalent to tablet use in children in rats, but the timing of puberty in rats is roughly equivalent to that in humans, if adjusted for the shorter life expectancy of the rats.
Hormonal and ovulation changes that occur during prepuberty and puberty in female rats are also comparable to those in humans. So, despite the limitations of the study, these results support further investigation of the potential impacts of blue light exposure on hormone levels and the onset of puberty in boys.
The team plans to investigate the cell damage and inflammatory effects seen after longer exposure to blue light, as this could have long-term repercussions on reproductive health and fertility. They will also assess whether the use of mobile devices with "night light" that minimizes blue light can reduce the effects seen in the rat model.
Dr. Aylin Kilinç Ugurlu adds that "although it is not conclusive, we advise that the use of blue light-emitting devices be minimized in prepubertal children, especially at night, when exposure can have more hormone-disrupting effects." .