Preliminary Results: The Impact of Smartphone Use and Short-Wavelength Light during the Evening on Circadian Rhythm, Sleep and Alertness

Round 1

Reviewer 1 Report

The manuscript is very detailed written in scientific way and with fluent English language. The article tries to answer question whether blue light filters of smartphone can attenuate negative effects of hormonal secretion (melatonin and cortisol), thermoregulation, sleep quality (slow wave sleep amount) and morning alertness (KSS questionary). This is not easy project and I think that they have put up huge research experiment, which is presented very clearly.

I have few concerns, which need to be answered:

Question 1:

You made three PSG recordings. How the adaptation night was done with or without electrodes?

Question 2:

Is results calculated as an average of these day 7, 10 and 13 measurements?

Question 3:

At what time of year your 14 participants were examined? Can there be seasonal rhythm effects among subjects?

Question 4:

If adaptation night can be some kind of baseline night is there among subjects any difference in sleep structure parameters between experimental nights or average of them?

Question 5:

Have you tried to calculate sleep fragmentation index to point out the effect of blue light filter ON /OFF?

You presented very clearly your results and discussed them carefully, still the main conclusion is not so clear and evident. But your have made enormous study and it is worth of publishing as an example how these kind of research should be done. You have taken many things account, but please discuss still a little about the effect of seasonal rhythms in case of your study.

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

High  value of this research is associated with comprehensive attitude toward the scientific problem of the influence of the use the smartphones for the  prolonged time before nighttime sleep on the subjective sleepiness and objective measurements of hormonal status, thermoregulation and neurophysiologic  sleep structure. It is perfectly constructed and performed, although on relatively small group of participants. Nevertheless the results are important not only from scientific point of view but also might be a basis for future studies  leading to the results that may importantly influence our –and especially young society population – every-day living habits.

Author Response

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Reviewer 3 Report

I have studied the paper "preliminary results: the impact of smartphone use and short-wavelength light during the evening on circadian rhythm, sleep and alertness" submitted to Clock&Sleep by Dr. C. Hoehn, et al. and I must state that I really enjoyed reading this paper.

Contents are clear and the statistical methodology fair (actually I have not been able to find a mistake!). The major limitation -that forces me to judge this paper as "average paper" (while it could truly deserve more otherwise)- is that the statistical amount of investigated subjects is very tiny (and I think that the adjective "preliminary" in the title reflects this flaw), but, in principle the analysis is sound and it is absolutely reasonable to me to infer the conclusions the authors wrote by a glance at their plots,  hence I do not have major concerns (beyond the small number of patients).

A minor point is that I found the last two statements in the Discussion (at the end of sec.3, before subsection 3.1 starts), where the authors write "Overall, no consistent benefit of the blue .... " up to the end of the section, namely "...when a blu light filter was used" a bit antithetical, please check the logical agreement among the two sentences.

If I can add a comment, in the "limitation and future direction" section, I would also add a small discussion on the need for larger datasets. To me, the ideal thing would be to perform finite size scaling analysis for checking the robustness of your results as the size of the analyzed patients increases (aiming at monotonic behavior of your curves), but this is clearly an entirely different level of research and can not be addressed here, you can at most just write a few lines here if you think that increasing the statistics is actually a future direction.

Author Response

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Round 2

Reviewer 1 Report

Thank you for your responses to my questions. Your modifications made this paper even more clear and plain to read.

I do not have more comments.

Reviewer 3 Report