Title: Factors associated with regularity and length of menstrual cycle: Korea Nurses’ Health
Study
Version: 1 Date: 06 Jun 2022
Reviewer:  Md Nuruzzaman Khan
Reviewer's report:
Many thanks for the invitation and I am sorry for being late in submitting the revision. I also
thank the authors to address this important issue in their research. I had a few comments which
are presented below. I believe they will help the authors to improve this manuscript. Very good
wishes!
1. The authors should include a few more literatures from their own study setting and describe
how this study is necessary. Currently, this is missing through I found there are some literature
published in this study setting.
2. Justification to conduct this study need to be strongest.
3. The last paragraph (aim section) of the Introduction section needs to be revised. This is not
clear now.
4. This study sample is 20-45 aged women. The menstrual circle is mostly irregular at a late
age or at an earlier age. However, the authors have not had these data, for instance, they do
not have any data for women aged <20 years or aged more than >45. The exact prevalence of
menstrual irregularities should be higher if these two groups are included in the analysis. The
authors need to add this issue in the limitation section. Also please consider adding a similar
sentence in the introduction and abstract section, so that readers can understand easily that the
reported prevalence does not necessarily represent all reproductive-aged women.
5. I am not sure whether it is logical to exclude women who had given birth or breastfed within
the last six months. I know exclusive breastfeeding suppresses menstruation; however, this is
not true for all women. For many women menstruation back within 2/3 months of delivery.
Moreover, the exclusive breastfeeding percentage is comparatively lower in your study setting.
6. As like point 5, I had similar concerns about excluding the cancer patients. Many cancer
patients have a normal menstrual cycle. I think a better approach should be to ask women when
they had their last menstruation and analysis this data. I hope the authors have this data.
7. The authors presented one exclusion criteria in the data collection section that need to move
to the study population section where the authors presented other exclusion criteria.
8. I am not sure what the authors mean by the term “eleven physical activities”. Did the authors
have any specific physical activities list at the time of data collection? Authors need to explain
clearly.
9. Did the authors use any test to measure whether the scores generated is good enough to be
considered in this study?
10. Authors cited only one paper in the statistical analysis section that they used to select the
covariates. This is very unlikely. Please revise this and add all relevant literature need to be cited
in this section. Also, consider moving this sentence to the covariates section.
11. Results section is now heavily weighted. Authors should revise this section and delete less
useful findings. This will help the readers to easily understand this paper.
12.  When BMI was measured, in the first round? For this study, you need data on survey time
BMI. If not available, then please write clearly about the implications of this limitation.
13.  Discussion needs to be revised by giving more focus on the policy and programs that need
to be taken to improve the situation.