No Effect of Chronotype on Sleepiness, Alertness, and Sustained Attention during a Single Night Shift

Round 1

Reviewer 1 Report

In the present study the Authors aimed to compare the effect of chronotype (determined from dim light melatonin onset, DLMO) on sleepiness and alertness (subjectively-measured) and sustained 80attention (objectively-measured using the PVT) over the course of a simulated night shift following a period of wakefulness.

Overall, I found this study timely, original, well conducted and scientifically sound. I have only some minor suggestions aimed to improve the high quality of the paper and these are outlined below:

1) In the introduction, a brif note on melatonergic receptors and their interactions with other neurotransmitters would be useful to he reader citing appropriate reference (see doi: 10.3390/ijms140612458).

2) Participants were 72 young, healthy adults (36 226females, 36 males) with a mean (± SD) age of 23.1 (± 3.6) years and body mass index (BMI) 227of 21.5 (±1.9) kg/m2, recruited by advertisements posted at hostels, student accommoda-228tion and university campuses, and on casual employment websites. Please note that this was a convenience sample.

3) Was body mass index (BMI) objectively measured or self-reported?

4) Was also an intellectual disability assessed and used as exclusion criterion?

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors have provided data showing that chronotypes did not affect sleepiness, alertness and other night-time performances, in contrast to field studies. The results are convincing. I have a few concerns:

1. Because of the findings as recapitulated above, I suggest the Title of this paper may be changed, because it is read as if chronotypes do affect certain parameters.
2. The participants of this study were both young and relatively thin. The authors did discuss somehow on the age factor in the last part of Discussion; how about BMI? Do the authors expect BMI variation would affect the measured parameters?
3. I suggest a final paragraph of Conclusion can be put after all the discussion.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

The authors have conducted an interesting study. I congratulate them on the successful completion of their work. There are few comments in the attached documents relating to my concerns and suggestions. I would like to see them addressed before the manuscript can be accepted for publication.

Comments for author File: Comments.pdf

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The paper is very interesting and worthy of publication 

Reviewer 2 Report

Revision done

Reviewer 3 Report

Thank you for responding to my comments/concerns. I do not have any further comments. All of my concerns have been well addressed.
However, the authors may want to consider briefly reporting sex effects, if there were any or none.