Research presented as part of a conference abstract at the European Society of Endocrinology annual meeting suggests that sleep in teenagers can be improved by one week of limiting their evening exposure to light-emitting screens.
Prof Malcolm von Schantz, Professor of Chronobiology, University of Surrey, said:
“This looks like an interesting study of an important topic. As the press release is based on an upcoming congress presentation, and the data have not yet been peer reviewed and made available through a published article, it is impossible to draw any conclusions from it at this stage.”
Prof Kevin McConway, Emeritus Professor of Applied Statistics, The Open University, said:
“On the face of it, this new research looks as if it might have found something interesting, but there are several reasons why it might not have. For one thing, it’s based on a conference abstract, so all we have is the abstract and a press release, and neither of those contains all the details that I’d want to check on evaluating the research. Also, it won’t yet have been through full peer review, so I can’t be confident that other scientists have checked things either. But I have several other concerns too. I’ll mention some issues that are covered in the information we already have, that suggest other possible interpretations of what was found. The differences in sleep patterns between frequent and infrequent screen users might be caused by the differences in screen use, or they might have nothing to do with that. And the improvements in sleep, when the frequent users wore glasses that cut out blue light, or when they did not use screens for a week, might have been caused by the special glasses or the avoidance of screens, but there are other potential reasons for those improvements in sleep that might explain the findings at least in part.
“The study was in two parts. In the part that really was a randomized trial, 25 adolescents, who had previously been identified as frequent screen users, had various aspects of their sleep and their melatonin levels measured after a week of their usual screen use, a week of wearing glasses that blocked blue light, and a week of not using screens. (I assume that different participants had these three treatments in a random order, though the descriptions don’t clearly say so.) The researchers report that wearing the special glasses and avoiding screen use were both followed by improvements in sleep, though most of the statistical details are not yet given. One snag with this set-up is that the adolescents involved knew that they were wearing glasses or avoiding screens, and this knowledge might in itself have led to changes in sleep. Perhaps making another set of measurements, with different special glasses that didn’t block blue light, might have clarified what was actually causing the improvements in sleep. Also, we aren’t told whether the amount of screen use was reduced when the participants were wearing the special glasses, so it’s hard to be sure whether the sleep improvements when the glasses were worn were caused by the reduction in blue light or changed screen use. And, even if the better sleep after avoiding screen use was actually caused by the reduction in screen use, there seems to be no clear way to tell whether that’s because of the reduction in exposure to blue light, or because the participants did something else that helped their sleep in the time when they would have been using their screens. Finally, a comparison with sleep when participants were wearing the special glasses and also avoiding screen use would have been helpful too, perhaps. Some of these points might be clarified when the full study report is available, but they won’t all go away.
“The other part of the study was not a randomized trial at all. It involved comparing sleep patterns in participants who recorded frequent and infrequent screen use. That part is an observational study, and observational studies are never easy to interpret. The problem is that there will be several other differences between the frequent and infrequent screen users, as well as differences in their screen use. If nothing else, the infrequent users must have been doing something else with the time when they weren’t using screens. But there were almost certainly many other differences as well. The reported differences in sleep patterns between these two groups could have been caused by one or more of these other differences between the groups, and not by screen use at all. We just can’t tell. It’s possible to make statistical adjustments that might allow for some of these other differences between the groups, but the information available so far doesn’t say whether any such adjustments were made. In any case, it’s impossible to know whether such adjustments have taken full account of all the other relevant differences, because it’s not possible to tell what all the relevant differences are.”
Dr Iroise Dumontheil, Reader of Cognitive Neuroscience at Birkbeck, University of London and researcher on the Study of Cognition, Adolescence and Mobile Phones (SCAMP) says:
“While this study has not been peer-reviewed and published yet, the findings are certainly promising. The results suggest that wearing blue-light-blocking glasses may reduce the impact of frequent screen use on adolescents’ sleep. Particularly interesting is that wearing these glasses had a similar effect to avoiding screen use completely, both allowing adolescents to fall asleep and wake up earlier. One caveat is that the study did not include an active control condition (e.g. wearing another type of glasses), therefore adolescents’ expectations may have contributed to the results. More work will be needed to check the effect can be sustained over time, but the findings do suggest that using technology to reduce exposure to blue-light may reduce negative impact of screen use in adolescence on sleep and well-being more generally.”
The abstract ‘Restoring the sleep disruption by blue light emitting screen use in adolescents: a randomized controlled trial’ by Wisse P. van der Meijden et al. was presented at the European Society of Endocrinology annual meeting.
Prof Malcolm von Schantz: No conflicts of interest.
Prof Kevin McConway: Prof McConway is a member of the SMC Advisory Committee, but his quote above is in his capacity as a professional statistician.
Dr Iroise Dumontheil: No conflicts of interest.