Blue light from phones and tablets may alter hormone levels and increase the risk of early 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 get older, their melatonin levels naturally drop to allow for the onset of puberty.
Scientists now believe that melatonin suppression resulting from smartphone use may put children at risk of experiencing an earlier puberty, impacting future fertility.
Their findings come from a rat study presented at the 60th Annual Meeting of the European Society for Pediatric Endocrinology.
dr. Aylin Kilinc Ugurlu, of Ankara City Hospital in Turkey, one of the researchers involved, said: “Since this is a rat study, we cannot be sure that these findings will be replicated in children, but these data suggest that blue light exposure can be considered a risk factor for the onset of puberty.”
The researchers used a rat model to see whether exposure to blue light had any effect on reproductive hormone levels and the time of puberty onset in female rodents.
The laboratory animals were divided into three groups of six and exposed to either a normal light cycle, or six hours 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 time, the earlier the onset of puberty.
Decreased melatonin levels and increased 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, showing signs of cell damage and inflammation.
Dr Kilinc Ugurlu said: “We have found that exposure to blue light, sufficient to alter melatonin levels, is also able to alter reproductive hormone levels and induce earlier pubertal onset in our rat model.”
The researchers said their findings merit further investigation into the possible effects of blue light exposure on hormone levels and the onset of puberty in children.
dr. Kilinc Ugurlu added: “Although inconclusive, we would advise that the use of devices that emit blue light should be kept to a minimum in prepubescent children, especially in the evenings when exposure can have the most hormone-altering effects.”
Commenting on the findings, Dr. Amy Orben, program leader, track scientist at the MRC Cognition and Brain Sciences Unit, University of Cambridge, who was not involved in the study: “The impact of blue light on young people and sleep is still under-researched and unclear, even in humans. .
“This study in rats gives us little to no evidence about what would be found in human children.
“Furthermore, exposure to pure blue light for extended periods of time is not an accurate representation of young people’s screen use.
“This is especially true for the 12-hour blue light condition in the study, which would have provided a very stressful environment for the rats.”