Blue light from phones and tablets can alter hormone levels and increase the risk of precocious puberty in children, early research suggests.
Blue light is thought to suppress the secretion of melatonin, a hormone that helps control the sleep cycle and is also associated with delaying the onset of puberty in young children.
As children age, their melatonin levels naturally decrease to allow for the onset of puberty.
Scientists now believe that suppressing melatonin following the use of smartphones could risk children experiencing precocious puberty, with implications for future fertility as well.
Their findings come from a rat study presented at the 60th annual meeting of the European Society of Pediatric Endocrinology.
Dr Aylin Kilinc Ugurlu, of Ankara City Hospital in Turkey, one of the researchers involved, said: ‘As this is a study in mice, we cannot be sure that these results are being replicated in children, but these data suggest that blue light exposure could be considered a risk factor for early onset of puberty.
The researchers used a rat model to see if blue light exposure had any effect on reproductive hormone levels and the time to onset of puberty in female rodents.
The lab creatures were divided into three groups of six and exposed to either a normal light cycle or either six or 12 hours of blue light.
The team found that the first signs of puberty were “significantly earlier” in the two groups exposed to blue light.
They also found that the longer the exposure duration, the earlier the onset of puberty.
Reduced levels of melatonin and elevated levels of two specific reproductive hormones – estradiol and luteinizing hormone were also observed in rats exposed to blue light.
There were also physical changes in their ovarian tissue, with signs of cell damage and inflammation.
Dr Kilinc Ugurlu said, “We found that exposure to blue light, sufficient to alter melatonin levels, is also capable of altering reproductive hormone levels and causing early onset of puberty in our rat model.” .
The researchers said their findings warrant further investigation into the potential impacts of blue light exposure on hormone levels and the onset of puberty in children.
Dr. Kilinc Ugurlu added: “Although inconclusive, we recommend minimizing the use of blue light emitting devices in prepubertal children, especially in the evenings when exposure can have the most hormone-altering effects.”
Commenting on the findings, Dr Amy Orben, lead scientist of the program at MRC Cognition and Brain Sciences Unit, University of Cambridge, who was not involved in the research, said: “The impact of blue light on young people and sleep is still under-researched and unclear, even in humans.
“This rat study gives us little or no evidence on what would be found in human babies.
“Further, exposure to pure blue light for long periods is not an accurate portrayal of young people’s screen use.
“This is especially true of the 12 hours of blue light in the study, which would have created a very stressful environment for the mice.”