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expert reaction to an unpublished conference abstract on blue light exposure and puberty onset in mice

A conference abstract, presented at the European Society for Paediatric Endocrinology Meeting, discusses blue light exposure and puberty onset in mice.


Prof Stuart Peirson, Professor of Circadian Neuroscience, University of Oxford, said:

“I am surprised this is raised, as an unpublished abstract from a small conference, rather than once it is a published paper.

“Without attending the meeting or seeing the data I cannot accurately judge the science, but from the available information in the abstract, it would be overclaiming to say these findings have any significant relevance to humans, their screen use and puberty.

“LED phone screens emit white light, which is slightly blue enriched. This study appears to use a pure blue LED, which does not reflect screen exposure at all. They do not state the time of day of exposure, but presumably this is during the dark phase for 6h or 12h. They do not use a control light exposure, but exposure to white light would likely exert the same effects.

“Moreover, the translation from rats to humans is not straightforward. Rats are nocturnal rodents and light exposure during their normal active phase is likely to be a chronic stressor. Finally, no underlying mechanisms or pathways mediating these effects are proposed. Melatonin is a biological marker of night-time, and does not drive sleep. Indeed, in nocturnal rodents melatonin levels are high when animals are awake and active, and low when they sleep. In many seasonally breeding animals, daylength determines breeding status, and this is encoded by melatonin.”


Prof Kevin McConway, Emeritus Professor of Applied Statistics, The Open University, said:

“This study is rather hard to assess because we don’t have the full paper, only a fairly brief abstract and a press release. I’ve no specific reason to think that there were any issues in the conduct of the experiment or in its statistical procedures to cause concern, but without the full paper, I can’t be sure that it was all fine. Nothing is said in the available information about what kind of peer review it might have had – typically, conference papers like this would not have had full peer review yet.

“But the main reason to be very cautious in interpreting the results in relation to human children is that the study was done on rats, not humans, and the researchers make it clear that exposure to blue light in the rats was not the same as would happen in human children using smartphones, tablets or PCs. The researchers, rightly, are not claiming any more than that their findings suggest that blue light exposure may be a risk factor for early puberty in human girls. I’m no expert on how similar the reproductive physiology of pre-adolescent female rats is to that of human girls, but certainly the pattern of exposure of the rats sound a bit different from what you might expect for human girls. The rats were exposed to blue light, seemingly to the exclusion of any other light, for either half or all of the light time of each of their days. (For comparison and control purposes there were also rats that were not exposed to blue light at all.) Also it may be relevant that wild rats are mainly nocturnal, and despite the behaviour of some young humans I’ve met, humans do tend to be rather less nocturnal, so that responses to light of any kind in rats and in humans may not necessarily match.”


Prof Pete Etchells, Professor of Psychology and Science Communication, Bath Spa University, said:

“This is a report of an unpublished study that has been presented at an academic conference, and while this is a perfectly valid stepping stone in the research lifecycle, we must be very cautious in interpreting any study that has not yet gone through the necessary checks and balances of peer review. Unpublished and unreviewed research should be heavily caveated in the media, if it is going to be covered at all. Unfortunately, the press release here does not do a particularly good job of representing the underlying science. The press release talks at great length about the proposed impact of blue-light-emitting devices such as smartphones and computer tablets, in terms of sleep quality and puberty onset in human children. However the study itself looks at the effects of quite intense and prolonged levels of blue light exposure on puberty onset in rats. Because this is not a published study, it is difficult to ascertain the methodological robustness of the work, as very few methodological details are given and no data sets are available to assess. But it does not seem to me that the blue light exposure levels used are meaningfully comparable to those encountered by humans during the course of everyday digital device use. As it stands, this study doesn’t appear to tell us anything meaningful about digital technology use in children, or the effects of blue light on sleep or puberty.”


Dr Amy Orben, Programme Leader Track Scientist, MRC Cognition and Brain Sciences Unit, University of Cambridge, said:

“The impact of blue light on young people and sleep is still under-researched and unclear, even in humans. This study done on rats give us little to no evidence about what would be found in human children. Further, pure blue light exposure for long durations is not an accurate portrayal of young people’s screen use. This is especially the case for the 12 hours of blue light condition in the study, which would have made a very stressful environment for the rats. 

“For parents who are worried about their children’s screen use, I would recommend the Royal College of Paediatrics and Child Health screen time guidance for clinicians and parents:



The abstract ‘Blue Light Exposure and Exposure Duration Effects on Rats’ Puberty Process’ is being presented at the European Society for Paediatric Endocrinology Meeting.


Declared interests

Prof Stuart Peirson: No declarations of interest

Prof Kevin McConway: “I am a Trustee of the SMC and a member of its Advisory Committee.  My quote above is in my capacity as an independent professional statistician.”

Prof Pete Etchells: PE is the author of Lost in a Good Game, and of the forthcoming book Screens Are Not Your Enemy.

Dr Amy Orben: No declarations of interest


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