It is known that many girls – and even boys – around the world are reaching puberty much earlier than before. It is usually due to the brain dispatching sending signals to the sex organs earlier than it should, but other causes blamed for it include greater exposure to endocrine-disrupting chemicals found in food, plastics, and personal-care products; obesity; a richer diet; and even stressful or abusive home environments.
Sometimes it is due to genetics, or rarely, there is a problem in the brain, such as an injury or tumor, or in the thyroid, adrenal, or sex glands.
Now, scientists in Turkey have documented another possible cause – exposure to blue light from smartphones or tablets, which led to precocious puberty in male rats.
The researchers who recently presented their findings at the 61st Annual European Society for Pediatric Endocrinology Meeting in the Hague were the first to investigate the link between blue-light exposure and early puberty in male rats.
They published their study in the journal Frontiers in Endocrinology under the title “Endocrine Disruptors Affecting the Human and Companion Animal Endocrine Functions – Similarities and Indicators in ONE Health Concept. The research shed light on how environmental factors, such as screen time, impact early puberty and testicular tissue, which could eventually lead to future prevention strategies for children.
The main source of natural blue light during the day is the sun. It improves cognitive functions, mood, and alertness in the daytime. However, artificial blue light sources at night such as fluorescent, LED, and that from TV screens have become prominent throughout the previous century. During the last decade, people of all ages have expanded the usage of touchscreen devices like tablets and smartphones. These mobile touch devices emit high-energy, short-wavelength blue light, they wrote.
“Because of the reduced eye-screen distance, blue-light exposure is more substantial with these items. In recent years, the age of use of these devices in children has fallen rapidly. We know that blue light at night has a suppressive effect on melatonin, and – in comparison to the impacts of other light wavelengths – the blue light had the most suppressive effect on melatonin. It is also a stress factor and induces oxidative processes in tissues.”
Several studies have reported increases in early puberty onset for both girls and boys during the COVID-19 pandemic, as children increased their use of blue light-emitting devices, but this is very difficult to investigate in children.
Researchers examined 18 male rates for their study
Now, the researchers from the Ankara Bilkent City Hospital and Gazi University in Turkey examined 18 male rats aged 21 days old that were divided into three groups of six and exposed to either a normal light cycle, to six hours or 12 hours of blue light.
The researchers found that the first signs of puberty occurred significantly earlier in male rats exposed to blue light. Additionally, the longer the rats were exposed to blue light, the earlier their puberty started, while they also showed suppressed sperm development and damaged testicular tissue.
A previous study from the same group has also shown an earlier onset of puberty in female rats due to blue light exposure. However, this association has never been studied in male rats before. “For the first time, we found a direct relationship between blue light exposure and early puberty in male rats,” said lead researcher Dr. Aylin Kılınç Uğurlu from Ankara Bikent City Hospital. “Our findings align with our previous work on female rats, which also showed similar effects, thereby providing a more comprehensive view of how blue light may influence puberty in both male and female rats.”
While the findings suggest that blue light exposure could potentially be a risk factor for earlier puberty onset, more research is needed. “I want to emphasize that this is a rat study, and direct results cannot be interpreted for humans. However, we provide an experimental foundation to further investigate the health consequences of ever-increasing screen time in modern society,” said Kılınç Uğurlu.
The researchers will next focus on assessing the impact of blue light exposure before puberty in adult rats. “We aim to expose both male and female rats to blue light before puberty and understand its long-term effects on reproductive organ damage and fertility,” concluded Kılınç Uğurlu. “Ultimately, this research could lead to preventative measures and contribute to the ongoing discourse on how modern lifestyles affect physiological development and long-term health.”
