Review for 10.1186/s12876-018-0872-1 (2018)

Reviewer ’s report  
Title: Quantifying the effects of aging and urbanization on major gas trointestinal diseases to 
guide preventative strategies  
 
Version: 1 Date: 21 Jul 2018  
 
Reviewer: Yee Hui Yeo  
 
Reviewer's report:  
In this article, Liu est imated the impact of aging and urbanization on major GI diseases. The 
author derived and compared data from the 2004 and 2011 data sets of the National Disease 
Mortality Surveillance System. Urbanization pose positive and negative impact on people's 
health . Although urbanization is associated with elongated life expectancy and thus higher rate of 
diseases that occur in elderly group, it is unclear to know how the combination of urbanization 
and ageing affect the cause of death. Liu's study provided populati on-based findings on this 
issue.  
 
Major comments:  
1. The author needs to provide the sampling method of the 2004 and 2011 data sets of the 
National Disease Mortality Surveillance System and ensure the comparability between 
these two set. This is important because the different sampling method could bias the 
results and lead to spurious conclusion.  
2. The number of death by etiology can by affected substantially by the diagnostic 
performance of relevant tools and the coverage of mass screening of disease. F or example, 
the improved diagnostic technique in 2011 compared to 2004 may spuriously increase the 
number of case.  
3. In China, it is common to see patients with more severe disease move from less urbanized 
areas to cities to seek for medical help. This co uld bias the conclusion that urbanization 
leads to the increase of certain diseases.  
4. The author needs to provide the name of urban and rural area/regions and the definition of 
urbanization, and the source of information to enhance the reproducibility of  this results.  
5. The discussion needs to be more robust, as there are only a few comparisons between the 
findings of current study and previous studies. The author needs to provide justification for 
the research findings.  
 
Minor:  
1. In abstract, the autho r need to explain what B>0 stands for.  
2. Table 3: the author may need to rearrange the order of columns into B, confidence 
intervals, then p -value.  
 
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 manus cript or would you recommend an 
additional statistical review?  
If an additional statistical review is recommended, please specify what aspects requ ire further 
assessment in your comments to the editors.  
I am able to assess the statistics  
Quality of written English  
Please indicate the quality of language in the manuscript:  
Not suitable for publication unless extensively edited  
Declaration of competing interests  
Please complete a declaration of competing interests, considering the following questions:  
1. Have you in the past five years received reimbursements, f ees, funding, or salary from an 
organisation that may in any way gain or lose financial ly from the publication of this 
manuscript, either now or in the future?  
2. Do you hold any stocks or shares in an organisation t hat may in any way gain or lose 
financially from the publication of this manuscript, either now or in the future?  
3. Do you hold or are you currently applying for any patents relating to the content of the  
manuscript?  
4. Have you received reimbursements, fees, funding, or salary from an organization that 
holds or has applied for patents re lating to the content of the manuscript?  
5. Do you have any other financial competing interests?  
6. Do you have any non -financial competing interests in relation to this paper?  
If you can answer no to all of the above, write 'I de clare that I have no competing interests' 
below. If your reply is yes to any, please give details below.  
 
I declare that I have no competing interests  
 
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on my rep ort to the authors and, if the manuscript is accepted for publication, my named report 
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to the editors, which will not be published.  
 
I agree to th e open peer review policy of the journal