Exposure to blue light through regular use of tablets and smartphones may alter hormone levels and increase the risk of precocious puberty, according to data from a rat study presented today at the 60th Annual Meeting of the European Society of Pediatric Endocrinology.. A longer duration of blue light exposure was associated with an earlier onset of puberty in female rats, which also showed reduced levels of melatonin, increased levels of certain reproductive hormones, and physical changes in their ovaries. . The use of mobile devices emitting blue light has already been linked to sleep disturbances in children. However, these results suggest that there may be additional risks to child development and future fertility.
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The increasing use of blue light-emitting devices, such as tablets and smartphones, has already been implicated in reduced sleep quality in children and adults. This is believed to be because blue light disrupts our biological clock, as it inhibits the rise in melatonin levels, the hormone that prepares our body for rest and sleep. Melatonin levels are generally higher during pre-puberty than during puberty, which is thought to play a role in delaying the onset of puberty. Puberty is a complex process that involves the coordination of several bodily systems and hormones.
In recent years, several studies have reported an increase in the early onset of puberty in girls, especially 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, may play a role in this reported increase. However, it is not easy to assess this phenomenon in children.
In this study, Dr. Aylin Kilinç Uğurlu and colleagues from Ankara, Turkey, used a rat model to investigate the effects of blue light exposure on reproductive hormone levels and timing of birth. onset of puberty. 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 appeared 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 showed reduced levels of melatonin, elevated levels of specific reproductive hormones (estradiol and luteinizing hormone), and physical changes in their ovarian tissue, all consistent with the onset of puberty. After 12 hours of exposure, the rats also showed some signs of cell damage and inflammation in their ovaries.
Dr Aylin Kilinç Uğurlu comments: “We found that blue light exposure, sufficient to alter melatonin levels, is also able to alter reproductive hormone levels and cause earlier onset of puberty in our rat model. Also, the longer the exposure, the earlier the onset. »
Although Dr. Aylin Kilinç Uğurlu cautions: “As this is a rat study, we cannot be sure that these results would be replicated in children, but these data suggest that exposure to blue light could be considered a risk factor for earlier onset of puberty. »
It is difficult to mimic blue light exposure equivalent to a child’s tablet use in rats. Nevertheless, the timing of puberty in rats is about equal to that of humans, if we take into account the lower life expectancy of rats. Also, the hormonal and ovulation changes that occur during pre-puberty and puberty in female rats are comparable to those in humans. Thus, despite the limitations of the study, these results argue for further investigation of the potential health effects of blue light exposure on hormone levels and the onset of puberty in children. children.
The team plans to study the cellular damage and inflammatory effects detected after longer exposure to blue light, as this could have long-term implications for reproductive health and fertility. She will also assess whether the use of blue light to minimize the nighttime lighting functions of mobile devices can reduce the effects observed in the rat model.
Dr. Aylin Kilinç Uğurlu adds: “Although this is not conclusive, we advise to minimize the use of blue light emitting devices in pre-pubertal children, especially in the evening, when exposure may have the greatest effect on hormones. »
Effects of blue light exposure and its duration on the puberty process of rats
Introduction : Over the past decade, blue light (BL) sources such as tablets and phones have increased across all age groups. Due in particular to the Covid-19 pandemic, exposure to screens has also increased in childhood. However, the effects of blue light exposure during puberty are unclear. We therefore sought to examine the impact of screen exposure and exposure time on puberty.
Methods : Eighteen 21-day-old immature female Sprague Dawley rats were divided into three groups consisting of six rats in each group: Control Group (CG), Experimental Group-1 (EG-1), and Experimental Group-2 (EG- 2). Rats in the CG group were maintained under standard conditions with 12/12 hour light-dark cycles. Rats in groups EG-1 and EG-2 were exposed to BL (450-470 nm/irradiance of 0.03 µW/cm2) for 6 hours and 12 hours, respectively. Rats were exposed to BL until the first signs of puberty appeared and were euthanized. Sera FSH, LH, Estradiol, testosterone, DHEA-S, leptin, and melatonin were studied by the ELISA method. The ovaries and uterus were dissected for histomorphological examination.
Results: Median days to puberty for CG, EG-1, and EG-2 were 38th32ndet 30th days, respectively. (p: 0.001) A negative correlation was found between the day of entry into puberty of the groups, the exposure to BL and the duration of the exposure. (r:-0.910, p
FSH, testosterone, DHEA-S, and leptin levels of all groups were similar. (p > 0.05) However, LH and estradiol levels of EG-1 were higher compared to CG. (p:0.027) There was a negative correlation between BL exposure, exposure time and melatonin levels (ro:-0.537, p:0.048). Ovarian tissue was consistent with puberty in all groups. As BL exposure time increased, capillary dilation and edema in the overtissue increased. Prolonged exposure caused polycystic-like (PCO-like) morphological changes and granulosa cell apoptosis.
Conclusion: Our study is the first to show the effects of exposure to BL on puberty. Our study showed that exposure to BL and duration of exposure leads to precocious puberty. In addition, PCO-like inflammation and apoptosis were detected in ovaries with increasing duration of BL exposure.
Studies show an increase in cases of precocious puberty and an acceleration in the rate of puberty during the lockdown period compared to the pre-pandemic period. Our study demonstrated the effects of BL exposure on puberty and the relationship between increasing exposure time.