Review for 10.1186/s12876-025-04029-0 (2025)

Title: Association Between Blood Lead Levels and Constipation in Adults: Insights from
NHANES Data (2005–2010)
Version: 0 Date: 24 Mar 2025
Reviewer:  Amirreza Jabbaripour Sarmadian
Reviewer's report:
Dear Authors;
Thank you for your efforts in conducting this valuable study, which I believe has the potential
to attract significant attention from experts in the field, public health professionals, and also
policymakers! This study investigates the association between blood lead levels and constipation
in adults based on the NHANES Data (2005–2010). The authors have utilized the NHANES
Data as the basis for their research, which is a strength of this study. However, to further improve
the study, the following points should be considered and also explained:
1) The title requires a revision. In my opinion, a more effective alternative could be "Association
Between Blood Lead Levels and Constipation in Adults: Insights from NHANES Data (2005–
2010)"
2) I have a question! Blood lead is a short-term marker, which may not represent chronic
exposure effects. In contrast, constipation is usually a chronic condition. Isn’t it a bias? If so talk
a bit about how long this marker can present the lead level and so on.
3) Revise the entire text to improve grammar, fluency, and clarity. The text contains multiple
grammatical issues and should be edited by a native English speaker. For example, consider
the following sentence "Although the causes of constipation are multifactorial, including diet,
lifestyle, genetic factors, and environmental factors such as heavy metal exposure, have also
gained attention.” The sentence starts with "Although," which typically introduces a contrast
or dependent clause, but the main clause is missing.  In addition, the phrase "have also gained
attention" does not have a clear subject, making the sentence grammatically incorrect. Before
mentioning abbreviations such as NHANES in the main text, it should be defined first, then use
the abb ones.
4) In my opinion, the introduction section needs revision. You should talk about the potential
pathophysiology of lead toxicity in gastrointestinal disorders. Besides, ensure proper citation
placement after each factual statement, especially when referring to previous studies that support
or contradict the findings. It would be better to use more recently published and relevant
references in several sentences. Try to highlight the challenging nature of constipation as a global
issue, which can also lead to other disorders.
5) The method section also has several grammatical issues. It is preferable to present the
excluded patients at the beginning of the Results rather than describing them in the methods
section. In the Methods section, include references when describing the NHANES study process,
particularly when discussing procedures such as blood sample collection and lead analysis.
6) First, if the normality of data was tested, briefly mention the method. If assumed, justify it.
Specify the exact variables included in Model 1. The number of knots used in the RCS model
is not specified. Also, it is unclear whether the model was adjusted for covariates. Specify the
subgroups analyzed (e.g., age, gender, BMI categories) and the method used for interaction
testing.
7) I have a concern about the methodology. NHANES provides specific instructions on how to
apply survey weights, especially when combining multiple cycles (2005–2010 includes three
cycles as you mentioned). Simply applying the Two-Year Interview Weight may not be correct
unless properly adjusted for multi-cycle analysis. In my opinion, you should clarify whether
you followed NHANES recommendations for combining weights across multiple cycles. If you
used a 6-year weight, explicitly state how it was calculated.
8) You should talk more about the possible cause of different conclusions with previous studies
in the discussion section, which may be due to age-dependent effects, exposure levels, and
constipation definitions.