Title: The relationship between pregnancy count and duration of breast-feeding with metabolic
syndrome (Fasa Persian Cohort Study)
Version: 1 Date: 14 Feb 2023
Reviewer's report:
"PEER REVIEWER ASSESSMENTS:
OBJECTIVE - Full research articles: is there a clear objective that addresses a testable research
question(s) (brief or other article types: is there a clear objective)?
No - there are minor issues
DESIGN - Is the current approach (including controls and analysis protocols) appropriate for
the objective?
No - there are major issues
EXECUTION - Are the experiments and analyses performed with technical rigor to allow
confidence in the results?
No - there are major issues
STATISTICS - Is the use of statistics in the manuscript appropriate?
No - there are issues with the statistics in the study
INTERPRETATION - Is the current interpretation/discussion of the results reasonable and not
overstated?
No - there are major issues
OVERALL MANUSCRIPT POTENTIAL - Is the current version of this work technically
sound? If not, can revisions be made to make the work technically sound?
Maybe - with major revisions
PEER REVIEWER COMMENTS:
GENERAL COMMENTS: In “The relationship between pregnancy count and duration of
breast-feeding with metabolic syndrome (Fasa Persian Cohort Study)”, the authors sought to
evaluate associations between parity and breastfeeding with metabolic syndrome risk in a large
cross-sectional study of women ages 35-70 years. This study has interesting data, but the
results are tempered by several flaws that need to be addressed and additionally the results and
discussion need to address potential biases in the data that were not addressed. Additionally, the
categorial variables should be re-visited as >12 categories for exposures is excessive and makes
results interpretation challenging.
Background:
- Additional discussion and citations about how breastfeeding can improve insulin resistance
is warranted.
- There is substantial heterogeneity in weight changes during the postpartum period.
- Some of the background about breastfeeding and metabolic syndrome could be presented in
a clearer manner.
- The energetic cost of breastfeeding is actually higher than 500 kcal (745+/-130 g/d) and it
depends on the stage of breastfeeding and the infants’ growth.
o https://pubmed.ncbi.nlm.nih.gov/2000814/
- Suggest adding additional background about parity and cardiometabolic health.
- There are also many papers that highlight how pregnancy is a “window into future
cardiovascular health”.
Methods:
- Provide a flow diagram from the larger cohort to the analytic sample.
o How many people were missing metabolic syndrome information?
- Was the cohort study originally designed to study this question or something else? How was
the sample size determined?
- What questionnaires were used? Just focus this section on study measurements relevant to this
manuscript.
- Was metabolic syndrome self-reported or were these measurements obtained as part of the
cohort study? How do self-report body size and metabolic syndrome compare to clinical
measures?
- I am concerned the metabolic syndrome criterion would not capture people who were on blood
pressure medication or other medications to treat metabolic syndrome components. This was
not addressed in the methods of analysis.
- Self-report of breastfeeding years may be prone to recall bias and does not reflect breastfeeding
intensity.
- If metabolic syndrome was a common outcome, logistic regression may result in overinflated
estimates of risk--suggest using other binary analysis methods if this is the case.
- Variables do not have level of detail needed. For example, for the variables smoking and
socioeconomic status it is not clear how these were coded.
- Breastfeeding and parity reference categories need further justification.
- Covariate/confounding adjustment explanation is inappropriate. There also may be age-related
effects and suggest examining whether results vary by age. Individuals ages 35-45+ may still be
having children and/or breastfeeding, and this analysis does not consider that or time postpartum.
Additionally, older women would have more time to develop metabolic syndrome.
- Sensitivity analyses were not conducted, including information about time since last delivery,
and whether or not participants were still breastfeeding.
Results:
- The results could be presented in a much more streamlined manner and figures could also be
more streamlined as well.
- Discussion of the role of medication and
Discussion
- The discussion does not flow well and needs to be re-written for readability, flow and clarity
and to reflect upon the results found in this study in a succinct and clear manner.
- Discuss limitations of the questionnaires about breastfeeding as those who are older age may
not as accurately recall breastfeeding history.
- Add more details about referenced studies – how does the study population in this cohort
compare to the referenced study population, how are they different, are the results similar or
different between this study and the prior research?
- There are many limitations of this work that are not denoted, including self-report of many
measurements.
- Conclusions should be tempered.
Tables/figures:
Need better labels and total sample sizes for each table and study population information.
Need to be streamlined.
The qual and quant labels are not needed.
Table 1 needs information on parity and breastfeeding duration overall in the sample and also
by metabolic syndrome categories. Suggest deleting the no column.
Table 2 is not clear – suggest categorizing # of pregnancies into meaningful categories, and
using this as an exposure variable; why was category 2 used as reference?
Table 4  - covariates and constant do not need to be shown in this table.
"