Review for 10.1186/s12876-020-01306-y (2020)

Reviewer’s report
Title: The influence of demographic characteristics on constipation symptoms: A detailed overview
Version: 0 Date: 15 Feb 2019
Reviewer: Paola Iovino
Reviewer's report:
In these paper Authors aimed to determine the specific patterns of constipation symptoms in different
demographic groups in a large population examining whether a more individual diagnostic approach
could  be  achieved.  Secondly,  they  aimed  to  define  the  symptoms  that  best  indicate  functional
constipation by investigating a wide range of constipation symptoms. 
They concluded that sex and age independently influence the likelihood of constipation in the general
Dutch population. There are different subtypes of constipation dependent on age.
This study is certainly important. However, given the explorative nature, observational research are
powered to detect small differences in the endpoint of interest and to allow for extensive adjustment for
confounding, performing subgroup analyses and to evaluate the contribution of several independent
variables to the variance in the outcome distribution. An important corollary of such considerations is
that the evaluation of clinical significance is always a key step for interpreting results in the field of
survey research. In fact, trusting solely on p-values is a common mistake and authors should be clear in
avoiding misleading conclusions from large observational studies. 
For example, I am wondering whether the inclusion of abdominal pain, could explain the result of a
higher prevalence of all constipation symptoms in the 18 to 38-year-olds. Specifically, in accordance
with the Rome IV criteria, abdominal pain may be present but are not a predominant symptoms.
Moreover, patients with FC should not meet IBS criteria. How did you assess the presence (intensity-
frequency) of abdominal pain? 
Moreover, details of the comorbidities which were assessed should be clearer : why did you  exclude
slow transit constipation and how were these patients diagnosed? 
Are the methods appropriate and well described?
If not, please specify what is required in your comments to the authors.
No
Does the work include the necessary controls?
If not, please specify which controls are required in your comments to the authors.
Yes
Are the conclusions drawn adequately supported by the data shown?
If not, please explain in your comments to the authors.
No
Are you able to assess any statistics in the manuscript or would you recommend an additional
statistical review?
If  an  additional  statistical  review  is  recommended,  please  specify  what  aspects  require  further
assessment in your comments to the editors.
I recommend additional statistical review
Quality of written English
Please indicate the quality of language in the manuscript:
Acceptable
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