Reviewer's report
Title:Effects of Rotating Shift Work on Moderate Exacerbation of Menstrual
Characteristics In A Population of Chinese Nurses: A Case Control Study With
Two-Year Followup
Version:4Date:30 May 2015
Reviewer: Bente Moen
Reviewer's report:
Comments on the manuscript
”Effects of Rotating Shift Work on Moderate Exacerbation of Menstrual
Characteristics In A Population of Chinese Nurses: A Case Control Study With
Two-Year Followup”.
This is a study of menstrual characteristics among nurses related to shift work.
The topic is of interest, as few studies exist on the subject. This is a shame, as
huge numbers of nurses work shifts and their reproductive health should be of
high interest.
However, the manuscript is very unclear on several issues, and needs a major
revision. Detailed comments are given here:
Major Compulsary Revision:
Title: The expression “moderate exacerbation” should be avoided, as this is
unclear.
Also the design is very unclear, case control and follow up stated like this make
no sense, and must be revised.
Abstract: This abstract must have a major revision when the manuscript itself has
been revised, many topics are unclear. For instance, the expression “two year
followup based on a cross-sectional study” should be changed. Actually, the
design is not possible to understand – see further down in the methods (of
manuscript). In methods (here in abstract), the expression “effective ones” is not
clear. It is unclear what the preliminary analysis is here, what is preliminary??
The method is very unclearly described.
Results are also very unclear, for instance what does it mean that “nurses in shift
group with regular 25-31 days cycle reduced..”? and in next sentence…”After
age adjustion (which should be the word adjustment, by the way)…nurses were
at more risk..” – what kind of risk is this?
The conclusion is not clear as the objective stated in the beginning of the
abstract tells about rotating shifts and those are not mentioned in this conclusion.
Also, the text in the conclusion is not easy to understand and should be changed
completely.
Introduction: The summary of methods at the end of the introduction is not clear.
The type of design is not possible to understand. Is this a cross-sectional study?
A cohort? A case-control study? Maybe it is a combination, but then you must
write this clearly. You may report from a cross-sectional study (part I) and then
from a cohort (part II), but the methods and results from these two pars must be
clearly separated.
It might be possible that the study is a “nested case-control study” or
“case-control study within a cohort”, this is a special design that need special
description.
Methods: -It is surprising to read that nurses at a hospital do not work night shifts
(in Guanghua Hospital), it is not clearly explained how this can be the situation.
Please explain more about this.
-How did you find out if the nurses met criteria for inclusion? Please describe.
-The design from this study is very unclear, as stated earlier.
-The questionnaire is only partly described. Please give details, or tell if the
questions are from validated instruments (in which case a reference should be
given). We do not understand what the nurses were actually asked! That means
we cannot evaluate the outcomes at all.
-It is not clear who the nurses in the subgroup of susceptible nurses were. The
expression “variable alteration of the mean length” is not defined, please do so.
-The definition of rotating shift work given seems to be totally different from the
one used in the rest of the world. Rotating shift work is when a nurse has a
schedule of day shift one day, afternoon shift next day, night shift the third day
and so on; a system repeating itself, only interrupted by days off. If the Chinese
system is different, please give exactly the descriptions of the way the shifts are
organized. This is important as the discussion needs to compare the results with
results from other studies – which may have other definitions of rotating shifts
than this present one. Then results are not comparable.
-Definitions of “menstrual cycle”, “dysmenorrhea” and “irregular bleeding” seem
to be chosen as dependent variables in the statistical analysis. These definitions
must be defined.
Figure 1: Figures are good for the purpose of clarification. This figure is
confusing. We need to know the sample and the design used, for instance how
the control groups were constructed. This figure mixes selection and results and
gives too many details we cannot handle. It must be simplified and revised. Also,
the figure legend repeats all details. This is not necessary. The legend should be
short and the information should be easily seen in the figure itself.
Results:-The expressions perceived job adjustment and perceived psychoneural
signs must be defined.
-In table 2 we see the division into “before” and “after”. What does this mean?
Several of the variables have No. in front of them. What does this mean?
Number? No? We need to know. One of the reasons for unclearness here is that
the questionnaire used in the study is unknown and we do not know what kinds
of questions were asked. With this information in the methods, the table might be
easier to understand. As it is now, the table is a mystery.
-In table 3 there are many analyses, but the hypotheses is not clear. The division
into three groups regarding cycle length, how did you decide upon them? And did
you want to study if the different shift work measures were associated to short
cycles? Or long? And why? Please state these explanations here or in
introduction or methods.
-In table 4 a subgroup is described. The problem is the selection of them. Why
did you select a group with normal cycles? Or did you? How did you find out that
the nurses had normal cycles during shift?? How was “variable alteration of the
mean length” of cycles defined? And how did you find out that the nurses had
this? All this is very unclear.
-Figure 2 and 3 are not possible to understand due to lack of definitions. Even
the long legends do not explain how you got the data you refer to; how were the
questions asked among the nurses?
Discussion: As the results are quite unclear, the discussion part is not easy to
perform. Probably this needs revision when the results have been clarified.
There is no need for details on mechanism here in this discussion; it is not clear if
the study has found any adverse effects at all on menstrual characteristics
related to shift work – especially not to rotating shift work.
In limitation it is stated that this is a cross-sectional study. Is it or is it now? This
must be clarified in the manuscript. It seems like the researchers need to consult
an epidemiologist for help on the study and the further evaluation/writing of the
manuscript.
The conclusion made must be revised and is not obvious at all.
Descretionary Revision
A few other references might be read and added in discussion:
-Baker F, Driver H-S (2007) Circadian rhythms, sleep, and the menstrual cycle.
Sleep Med 8, 13-622.
-Wan G-H, Chung FF (2012) Working conditions associated with ovarian cycle in
a medical center nurses: A Taiwan study. Jap J Nurs Sci 9, 112-118.
-Moen BE, Baste V, Morken T, Alsaker K, Pallesen S, Bjorvatn B. Menstrual
characteristics and night work among nurses. Ind Health. 2015 Apr 24. [Epub
ahead of print]
Level of interest: An article of importance in its field
Quality of written English: Needs some language corrections before being
published
Statistical review: Yes, and I have assessed the statistics in my report.
Declaration of competing interests:
'I declare that I have no competing interests'