For many years, the number of girls experiencing early puberty has risen dramatically, with more and more girls across the world showing signs of premature sexual development before the age of 8. By one estimate, around 10% of White girls and 23% of Black girls in the United States are now showing signs of puberty by age 7, such as breast development, and that’s a major health concern for a number of reasons. The pandemic has mysteriously exacerbated this trend with doctors reporting an overwhelming rise in the number of early puberty cases among girls.
Naturally, the first suspected culprit was the virus itself. But when they ran the numbers, public health experts found that even girls who were never infected started showing signs of early puberty in disproportionate numbers to what they were used to seeing. This trend was also apparent during the early months of the pandemic when coronavirus strains barely affected children. Next on the list was weight gain, a known risk factor for early puberty in both boys and girls, owed to increased sedentarism as a result of the lockdown, but studies showed that children didn’t actually put on extra weight during the pandemic.
So what gives? Researchers in Turkey have recently proposed a mechanism that may explain the pandemic-related surge in early puberty, which at first glance sounds outlandish but which should nevertheless be taken seriously considering the significant evidence they’ve gathered. They believe increased screen time — or rather increased exposure to blue light, to be more precise — may have triggered hormonal imbalances in very young girls, thereby triggering idiopathic precocious puberty, or extremely early onset of puberty.
Screen time and early puberty: what’s the connection?
Puberty is that tumultuous time in a person’s life in which they become sexually mature from a physical perspective. Normally, this process happens between ages 10 and 14 for girls and ages 12 and 16 for boys. During puberty, boys and girls undergo significant physical changes, which affect them differently. Boys grow a larger scrotum and penis, and their voices change, while girls develop breasts and begin menstruation.
It’s a pretty challenging period as teens have to cope with the fact that they’re morphing into what seems like a completely different body, at least compared to their preteen days. But for some, puberty starts much too early, and it can be a much more distressing experience for preteens.
Precocious puberty happens if girls are aged 8 or younger and boys are 9 or younger. It can happen due to a confluence of factors, including genetic syndromes, central nervous issues, or even tumors on the ovaries, adrenal glands, or brain. Between one in 5,000 and one in 10,000 children experience sexual precocity, with girls outnumbering boys by approximately ten to one.
During the pandemic, researchers have reported a surge in precocious puberty cases in many countries across the world, including the U.S., India, Italy, and Turkey. For instance, five pediatric endocrinology centers in Italy reported 300 girls with precocious puberty between March and September 2020, as opposed to 140 cases during the same period in 2019. In Turkey, a pediatric endocrinology clinic reported 58 cases in 2020, compared to 66 cases for the previous three years combined.
Many endocrinologists think that stress induced by the lockdown, which disrupted life and social activities, and the prospect of losing close family members is likely to blame for this worrisome uptick in early puberty among girls during the pandemic.
That may well very be the case, but a new study has found evidence that increased screen time may also be a significant contributing factor. In order to test this hypothesis, endocrinologists at the Gazi University and Ankara City Hospital in Turkey exposed 18 immature female rats to either a normal light cycle or blue light typically emitted by the LED screens of phones, tablets, and computer screens. The effect of blue light was tested in 6 hours or 12 hours of exposure.
The female rats exposed to both levels of blue light showed the first signs of puberty earlier than their counterparts exposed to natural light in a normal day-night cycle. The longer the duration of blue exposure, the earlier the onset of puberty. For instance, the female rats exposed to blue light had lower melatonin levels (the hormone that plays a key role in sleep) and elevated levels of oestradiol and luteinising hormone, both hormones related to reproduction. They also experienced physical changes in their ovaries. All of these signs are typical of the onset of puberty.
“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 study lead author Aylin Kilinç Uğurlu of Ankara City Hospital.
If you equivalate “rat years” with “human years”, in terms of life expectancy, both rats and humans typically start puberty at around the same age. The hormonal and ovulation changes occurring during both prepuberty and puberty are also very similar between humans and rats. However, Uğurlu cautions that rat models can never completely mimic the biology of humans, so there’s always the chance that these results only apply to rats. In fact, they usually don’t apply at all, as a 2006 review showed that only 37% of the most-cited animal studies (virtually the best studies) were replicated in subsequent human randomized trials.
That’s not to say that it couldn’t happen, though, as there are a lot of things that ‘click’. Blue light exposure is proven to inhibit melatonin production, which is why you find it hard to fall asleep after staying glued to your phone’s screen for hours just a few moments prior to bedtime. This disruption may potentially cause the body to ramp up certain hormones that produce a cascading effect in the body that may eventually trigger puberty earlier than it should.
“Although not conclusive, we would advise that the use of blue light emitting devices should be minimized in pre-pubertal children, especially in the evening when exposure may have the most hormone-altering effects,” Uğurlu said.
The findings were presented at the 60th Annual European Society for Paediatric Endocrinology Meeting