Concordance of Chronotype Categorisations Based on Dim Light Melatonin Onset, the Morningness-Eveningness Questionnaire, and the Munich Chronotype Questionnaire
Round 1
Reviewer 1 Report
It seems that subjective preferences as described with MEQ and self-reported sleep timing do not reflect precisely an individual’s biological clock functioning. One may suspect an under-estimated role of external social factors in shaping lifestyle habits described by MEQ and MCTQ. This issue may be a question to discuss in the appropriate section.
Materials and Methods
- line 228 – ”a 9-h sleep opportunity (23:00-07:00)” seems to be rather ‘an 8-h sleep opportunity’
- line 235 – 9-h sleep - ???
- lines 276-284 – the information about splitting the groups is a bit redundant (especially after reading pts. 2.2 and 2.3) – to be shortened
and the rest of 4.4 too…
Author Response
Please see the attachment.
Author Response File: 
Author Response.docx
Reviewer 2 Report
This is a well written concise paper examining the inter-relatedness of chronotyping via the MEQ, MCTQ and DLMO. Broadly the protocols are clearly described and the results presented in appropriate manner.
I do have some suggestions for a revision:
- The authors claim that they are unaware of other studies correlating biological and psychometric/behavioural measures of chronotype. This is an important mistake: Kantermann et al (2015) (Journal of Biological Rhythms, “Comparing the Morningness-Eveningness Questionnaire and Munich ChronoType Questionnaire to the Dim Light Melatonin Onset”) have undertaken a very similar analysis. Clearly this study needs to be included and discussed for the current results. There are a number of other studies that relate other measures of biological rhythms to MEQ/MCTQ measures that should also be noted:
“Molecular insights into human daily behavior. Brown SA, Kunz D, Dumas A, Westermark PO, Vanselow K, Tilmann-Wahnschaffe A, Herzel H, Kramer A. Proc Natl Acad Sci U S A. 2008
“In vitro circadian period is associated with circadian/sleep preference.” Hida A, Kitamura S, Ohsawa Y, Enomoto M, Katayose Y, Motomura Y, Moriguchi Y, Nozaki K, Watanabe M, Aritake S, Higuchi S, Kato M, Kamei Y, Yamazaki S, Goto Y, Ikeda M, Mishima K. Sci Rep. 2013;3:2074
“Diurnal Preference Predicts Phase Differences in Expression of Human Peripheral Circadian Clock Genes.” Ferrante A, Gellerman D, Ay A, Woods KP, Filipowicz AM, Jain K, Bearden N, Ingram KK. J Circadian Rhythms. 2015
- Further details should be provided on the days on which the laboratory procedures were conducted on. Were these “work-free” or “work” days for the participants. If DLMO was estimated on work days, this may have affected the relationships. How does DLMO correspond to MSW as well as MSFsc?
- The authors note that the participants were mostly tourists or students. For the participants who were tourists, did these have “work” days, or did they have regular work schedules for MCTQ purposes?
- The MEQ, MCTQ and DLMO scores were trichotimised, although insufficient justification for the validity of this approach was presented. How did the MEQ groups compare with groups created by the standard MEQ cutoffs for chronotypes? How did the MCTQ groups correspond to the self-assessed chronotype on the questionnaire? In general, I am not convinced of the utility of creating categories from the continuous scale variables.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
I am satisfied with the authors' response. Thank you.
Reviewer 2 Report
The authors have made sufficient responses to the points I raised in the original review.
