A Population-Level Analysis of Changes in Circadian Rhythms and Sleep and Their Association with Negative Emotions during the Outbreak of COVID-19 in China
Round 1
Reviewer 1 Report
The authors present an interesting study aimed at investigating the relationship between changes in diel rhythms and sleep and negative emotions.
- Introduction:
- I appreciate the logic proposed in the introduction; however, I think this paragraph is very short compared to the other sections of the paper.
- In my opinion, one of the main limits of the present works relies on the fact that no clear hypotheses have been formulated by the authors.
- Materials and method:
- The authors stated that: “The surveyed period was between Jan 20, 2020, and Jan 31, 2020, which comprised nine days after the emergency was launched.” Later, they reported that data were collected between 2, 2020, and February 3, 2020. To me it is unclear what is the first sentence meaning.
- The variables analyzed are not reported fully (e.g., demographic variables are not described). I would have also appreciated a more accurate description of the scales adopted.
- To me it is unclear why the authors did not decide to test a regression model.
- Results:
- In my opinion there are too many tables and graph. In this way the results become complicated to understand and many of the information presented are redundant. I think the reader could benefit from a reduction in the number of tables and figures.
- Given the nature of data collected and the analyses conducted, the interpretation of the relationship between sleep quality and emotions in terms of direct causality is not supportable. I would assume, reading the assertions proposed by the authors that negative sleep quality may influence participants emotions, but it is also possible to assume a reciprocal influence.
- Discussion and conclusion:
- In my opinion the authors should not only describe the results obtained, but also try to provide more explanations.
- The sentence “Our findings show that quarantine and concerns regarding the pandemic situation contributed to the changes in sleep, diel rhythms, and negative emotions.” is not appropriated because it empathizes the casual nature of the relationship.
- In the limitation paragraph, I would suggest mentioning the correlational nature of the study.
- I would also suggest focusing on the practical implication of the results obtained.
In conclusion, I think the article is interesting. However, in my opinion, some aspect of the paper should be reviewed.
Author Response
1) Introduction:
I appreciate the logic proposed in the introduction; however, I think this paragraph is very short compared to the other sections of the paper.
In my opinion, one of the main limits of the present works relies on the fact that no clear hypotheses have been formulated by the authors.
Re: We have added related content to the introduction and also emphasized the hypothesis of this work.
- Materials and method:
2) The authors stated that: “The surveyed period was between Jan 20, 2020, and Jan 31, 2020, which comprised nine days after the emergency was launched.” Later, they reported that data were collected between 2, 2020, and February 3, 2020. To me it is unclear what is the first sentence meaning.
Re: The mistake has been corrected. We have deleted the later part “between February 2, 2020, and February 3, 2020” to avoid confusion.
3) The variables analyzed are not reported fully (e.g., demographic variables are not described). I would have also appreciated a more accurate description of the scales adopted. To me it is unclear why the authors did not decide to test a regression model.
Re: We have added demographic description in the section of “Participants and ethics”, including the information of location, gender, age, occupation, and education levels (lines 99-115).
- Results:
4) In my opinion there are too many tables and graph. In this way the results become complicated to understand and many of the information presented are redundant. I think the reader could benefit from a reduction in the number of tables and figures.
Re: Thanks for your kindly reminding. The pandemic are affecting the people all over the world. When the pandemic began, we also realized we should consider as many factors as possible to obtain maximum valuable information which may help cope with the pandemic situation in the future. To this end we designed so many variables for analysis in this study so that we yielded many tables and figures. During this round of revision we also conducted regression analysis by following the comments which yielded another supplemental table.
You are right, we have a number of figures and tables. Relative to the tables, it is easier for the readers to read figures. So we put all the tables in the supplemental materials. We also removed Fig. 1A to the supplemental materials by following the comments. The reason that we did not delete these tables is that we think the readers can find the original results if you feel interested.
5) Given the nature of data collected and the analyses conducted, the interpretation of the relationship between sleep quality and emotions in terms of direct causality is not supportable. I would assume, reading the assertions proposed by the authors that negative sleep quality may influence participants emotions, but it is also possible to assume a reciprocal influence.
Re: We agree with you that these factors should have reciprocal influences. And we have conducted regression analysis which showed that potential casual inferences (lines 311-325). In addition, we also rephrased the related sentences in Discussion to make it more appropriate (lines 423-431).
- Discussion and conclusion:
6) In my opinion the authors should not only describe the results obtained, but also try to provide more explanations.
Re: We have added explanations regarding several issues and simplied the description of the results in the section of Discussion in the revised version. To support these explanations, additional references have also been added and cited.
7) The sentence “Our findings show that quarantine and concerns regarding the pandemic situation contributed to the changes in sleep, diel rhythms, and negative emotions.” is not appropriated because it empathizes the casual nature of the relationship.
Re: We have reworded this sentence to be “Our findings show that quarantine and concerns regarding the pandemic situation are associated with sleep, circadian rhythms, and negative emotions” (lines 443-445). We have also conducted regression analysis to compare the casual inferences between these factors, which are described in the text.
8) In the limitation paragraph, I would suggest mentioning the correlational nature of the study.
Re: We have added a sentence “In addition, although correlational analysis can suggest potential relationship between two variables, it cannot prove that one variable causes a change in another variable” (lines 440-441).
9) I would also suggest focusing on the practical implication of the results obtained.
Re: We have added the potential practical implication of the findings obtained in this work as “Due to the dramatically increased transmissibility of the new mutant Omicron of COVID-19, mandatory quarantine is reimplemented in many countries or regions [47]. According to our findings, measures to improve the circadian rhythms, e.g., optimization of the living schedule, enhancement of the indoor daylight and appropriate exercise, may be applied to alleviate the negative emotions and promote the public health”. But we think it may be better to place these contents in the section of “Conclusions and perspectives” (lines 442-455).
Reviewer 2 Report
Manuscript ID: covid-1611338
Title: A population-level analysis of changes in diel rhythms and sleep and their association with negative emotions during the outbreak of COVID-19 in China
Journal: COVID
Abstract
1) Line 16. Authors should replace “diel” with “circadian” here and throughout the manuscript.
2) Lines 17-18. Authors should add at least the number of females and males as well as the mean, standard deviation, and range of age of the whole sample.
Introduction
1) Lines 54-55. Authors should specify that that study was referred to the pandemic period.
2) Lines 69-71. This part should be deleted from the Introduction section.
Materials and Methods
1) Authors should clarify whether they used (or not) Chinese validated versions of these questionnaires.
2) Lines 89-90. Actually, the Morningness-Eveningness Questionnaire allows to assess the circadian typology.
3) Line 104. Authors should replace “subjects” with “participants”.
4) Lines 105-106. Authors should add the ethical committee report number.
Results
1) Lines 125-128. Participants are assigned to the chronotype they belong to according to the total score of the questionnaire and cut-off scores.
2) Figure 1A. It seems to me that this is a Table, not a Figure.
3) Authors report a very long and not-easy-to follow list of results.
Discussion
1) Authors should avoid to frequently report percentage values also in the Discussion section. On the contrary, I would suggest that they focus on the possible explanations of the results.
2) Line 343. Authors wrote “In Italy where the pandemic status was the most serious in Europe”. Authors should quote some data supporting this statement.
3) Authors should avoid repeating the Results within the Discussion.
4) Lines 410-412. Authors should report the questionnaire in appendix.
Conclusions
1) Lines 417-418. Authors should delete “This section is not mandatory but can be added to the manuscript if the discussion is unusually long or complex.”.
Author Response
Abstract
1) Line 16. Authors should replace “diel” with “circadian” here and throughout the manuscript.
Re: We have replaced the words throughout the manuscript by following your suggestion.
2) Lines 17-18. Authors should add at least the number of females and males as well as the mean, standard deviation, and range of age of the whole sample.
Re: The number and proportion of females and males have been listed in the section of “2.2. Participants and ethics”. Regarding the information of age, we did not collect the precise ages, instead in the questionnaire, a series of age ranges were given to the pariticipants for selection, e.g., a) <18, b) 18~25, c) 26~30, d) 26~30, e) 31~40, f) 41~50, g) 51~60 and h) > 60 (please see Supplemental File S1). Therefore, we could not provide the mean, standard deviation of their ages.
Introduction
1) Lines 54-55. Authors should specify that that study was referred to the pandemic period.
Re: The introduction has been largely revised according to your and the other reviewers’ comments.
2) Lines 69-71. This part should be deleted from the Introduction section.
Re: we have deleted this part and some other contents in this section have also been revised to make the logic chain clearer.
Materials and Methods
1) Authors should clarify whether they used (or not) Chinese validated versions of these questionnaires.
Re: The contents in the questionnaire have been validated by our university together with the ethical issue. We have added this information in the context at the end of the section “2.1. Measurements and procedures” as “The contents of the questionnaire have been validated by Sun Yat-sen University” (lines 96-97).
2) Lines 89-90. Actually, the Morningness-Eveningness Questionnaire allows to assess the circadian typology.
Re: We have reworded this sentence as “The questions assessing circadian typology were designed by referring to the Morningness-Eveningness Questionnaire” (lines 93-94).
3) Line 104. Authors should replace “subjects” with “participants”.
Re: We have substituted these words throughout the text.
4) Lines 105-106. Authors should add the ethical committee report number.
Re: Early in 2020, our work was approved by the university ethical committee, and it has been deposited as a formal document. It also has been approved to submit to a journal for publication. However, there was no report number on the approval file.
Results
1) Lines 125-128. Participants are assigned to the chronotype they belong to according to the total score of the questionnaire and cut-off scores.
Re: We designed the questions to assess the circadian typology by referring to the classic Morningness-Eveningness Questionnaire (MEQ), but we did not use the entire content of MEQ since too many questions may drive the participants impatient and obtain false feedbacks. We used arbitrary cut-off score according to their sleep on-set time: early-type, slept before 22:00; intermediate type, slept between 22:00 and 24:00; late-type, slept after 24:00. We have rephrased this sentence to be “To assess the changes in the circadian phases, we classified the participants into three chronotypes according to arbitrary cut-off scores based on their sleep onset time during the survey period as follows” (lines 134-136).
In addition, the term “diel” here has been changed to be “circadian” according to the previous comments.
2) Figure 1A. It seems to me that this is a Table, not a Figure.
Re: We have deleted the panel Fig.1A and moved it to the appendix as a supplemental Table S1.
3) Authors report a very long and not-easy-to follow list of results.
Re: The pandemic was a disaster to the people all over the world. When the pandemic began, we also realized we should consider factors as many as possible to obtain maximum valuable information which may help cope with the pandemic situation in the future. Therefore we designed so many variables for analysis in this study that the section of Results is very long and the manuscript has many tables and figures. To make it easy to follow, we have reorganized the tables in the appendix.
Discussion
1) Authors should avoid to frequently report percentage values also in the Discussion section. On the contrary, I would suggest that they focus on the possible explanations of the results.
Re: We have removed a number of percentages in Discussion, and use “the majority”, “most” to replace the percentages in the section of Discussion. And we added many sentences to discuss the findings by following the comments. We also removed Fig. 1A to the supplemental materials as a table instead of figure.
2) Line 343. Authors wrote “In Italy where the pandemic status was the most serious in Europe”. Authors should quote some data supporting this statement.
Re: To add more explanation and discussion about the findings in this work, many of the descriptions of pandemic situations in different countries (including Italy and U.S.) have been combined and related literatures cited (lines 350-352).
3) Authors should avoid repeating the Results within the Discussion.
Re: We have rephased many of such places in the section of Discussion.
4) Lines 410-412. Authors should report the questionnaire in appendix.
Re: We have added the questionnaire translated from Chinese in the appendix (Supplemental File S1).
Conclusions
1) Lines 417-418. Authors should delete “This section is not mandatory but can be added to the manuscript if the discussion is unusually long or complex.”
Re: It has been deleted.
Round 2
Reviewer 2 Report
Manuscript ID: covid-1611338
Title: A population-level analysis of changes in circadian rhythms and sleep and their association with negative emotions during the outbreak of COVID-19 in China
Journal: COVID
1) Authors’ response to my previous comment number 1 on the Materials and Methods section.
I was wondering whether Authors used a psychometrically validated version of each questionnaire for the Chinese population.
Author Response
Due to emergent occurrence of the pandemic, we designed the questionnaire temporarily and specifically for the assessment of variables during the Spring Holiday in China. Thus, it is not a psychometrically validated questionnaire so that it is inappropriate to calculate averages spanning different items. Thanks for this very reminding and comment, and we have carefully checked throughout the text and supplemental files and removed the contents including calculations between different items. The revisions include:
1) We have removed the calculations of averaged values in supplemental Table S11;
2) In the second paragraph, pp.7, "The averaged total scores in men and women were 1.97 and 1.90, respectively, For instance, with men showeding higher scores than women on stupefaction (men 2.05; women 1.89), downheartedness (men 1.97; women 1.85), depression (men 1.74; women 1.60) and anxiety (men 2.05; women 1.97)" has been rephrased as "Differentially reported negative emotions between men and women were also ob-served. For instance, men showed higher scores than women on stupefaction (men 2.05; women 1.89), downheartedness (men 1.97; women 1.85), depression (men 1.74; women 1.60) and anxiety (men 2.05; women 1.97)".
3) In the second paragraph, pp.7, "In addition, individuals with higher education levels reported more negative emotions (Figure 3C and Table S11). The age groups of 26-30, 18-25 and 31-40 years had the highest negative emotion averages, i.e., 2.26, 2.04 and 1.96, respectively (Table S11)" has been reworded to be "In addition, individuals with higher education levels reported more negative emotions (Figure 3C and Table S11)".
4) In the last paragraph, pp.10: "However, in this study, we found that the average score of negative emotions was slightly lower in women than that in men (Table S11), which may be attributed to the different culture in China [37], although direct evidence is lacking" has been changed to be "However, in this study, we found that overall, most of the average scores of negative emotions were slightly lower in women than those in men (Table S11), which may be attributed to the different culture in China [37], although direct evidence is lacking".
