Excessive smartphone screen time linked to earlier puberty onset

conference abstract, experimental study, rats

Reports and Proceedings EUROPEAN SOCIETY FOR PAEDIATRIC ENDOCRINOLOGY

Exposure to blue light, via regular use of tablets and smartphones, may alter hormone levels and increase the risk of earlier puberty, according to data from a rat study presented today at the 60th Annual European Society for Paediatric Endocrinology Meeting. Longer duration of blue light exposure was associated with earlier puberty onset in the female rats, which also showed reduced levels of melatonin, increased levels of some reproductive hormones, and physical changes in their ovaries. The use of blue-light-emitting mobile devices has previously been linked to disrupted sleeping patterns in children but these findings suggest there could be additional risks for childhood development and future fertility.

The escalating use of blue light-emitting devices, such as tablets and smartphones, has previously been implicated in reducing sleep quality in both children and adults. This is thought to be through disruption of our body clock as blue light inhibits the evening rise in levels of the hormone, melatonin, which prepares our bodies for rest and sleep. Melatonin levels are overall higher during pre-puberty than in puberty, which is believed to play a role in delaying the start of puberty. Puberty is a complex process that involves the coordination of several body systems and hormones.

In recent years, several studies have reported increases in early puberty onset for girls, particularly during the COVID-19 pandemic. The link between blue light exposure and reduced melatonin levels suggests that increased screen time, such as during the pandemic restrictions, may be playing a role in this reported increase. However, it is very difficult to assess this in children.

In this study, Dr. Aylin Kilinç Uğurlu and colleagues in Ankara, Turkey, used a rat model to investigate the effects of blue light exposure on reproductive hormone levels and the time of puberty onset. Female rats were divided into three groups of six and exposed to either 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. Rats exposed to blue light also had reduced melatonin levels and elevated levels of specific reproductive hormones (oestradiol and luteinizing hormone), as well as physical changes in their ovarian tissue, all consistent with puberty onset. At the 12 hours of exposure, rats also showed some signs of cell damage and inflammation in their ovaries.