Exposure to blue light, like that from smartphones or tablets, may accelerate bone growth and bone age, leading to early puberty in rats. This research, presented at the 62nd Annual European Society for Paediatric Endocrinology Meeting in Liverpool, sheds light on how the use of blue light-emitting devices could impact growth and development and raises important questions about the long-term health effects in children, who are increasingly exposed to screens from a young age.
As children grow and develop, long bones such as the femur progressively elongate at each end. These growing ends – areas of smooth, elastic cartilage known as 'growth plates' – eventually solidify which stops growth in height. Girls generally stop growing and reach their maximum height between ages 14 and 16, while boys finish their growth between 16 and 18 years of age. However, in recent years, several studies have reported a rise in early puberty in both girls and boys, in which they might grow quickly at first but often stop growing earlier than usual. One factor may be the increased use of blue light-emitting devices.
In this study, researchers from Gazi University in Turkey examined 18 male and 18 female rats aged 21-days-old, equally divided into three groups of six and exposed to either a normal light cycle, six hours or 12 hours of blue light until the first signs of puberty. They measured their length and femurs and found that the rats exposed to blue light had a faster growth, particularly in their bones, and started puberty earlier compared to those in standard light conditions.
Previous research from the same group has also shown that rats exposed to blue light have a higher risk of early puberty. However, this association has never been studied in bone growth and pubertal development before. "This is the first study to show how blue light could potentially influence physical growth and development, prompting further research into the effects of modern screen exposure on children's growth," said lead researcher Dr Aylin Kılınç Uğurlu.
Although Dr Kılınç Uğurlu warned: "As this a rat study, we cannot be sure that these findings would be replicated in children but our data suggest that prolonged exposure to blue light accelerates both the physical growth and maturation of the growth plate, leading to early puberty."
"While the increased growth may sound beneficial, our study also found that blue light exposure led to earlier structural changes in the growth plates of the rats' bones, suggesting an impact on long-term bone age," said Dr Kılınç Uğurlu. "This means their bones matured too soon which could potentially cause them to be shorter than average as adults."
The researchers are now planning to investigate how blue light exposure before puberty affects height and skeletal development in adult rats. "We want to explore the long-term effects of pre-pubertal blue light exposure and find out whether certain exposure durations or intensities have reversible or permanent effects on the skeleton later in life," said Dr Kılınç Uğurlu. "Ultimately, this research could lead to preventative measures for safe screen use during childhood development."
