Reviewer’s report
Title: Gastroesophageal reflux disease in a typical African population A symptom-based multicenter
study.
Version: 2 Date: 24 Jul 2019
Reviewer: Helena Nordenstedt
Reviewer's report:
This manuscript has substantially improved since initial review. Most comments have been addressed
adequately and sufficiently (and in some ways even "over-addressed", as in the case of physical activity
where the reviewer/reviewer's former research group needlessly has been extensively cited). 
However, some comments have not been addressed, and I would recommend giving the authors the
chance to further improve. Most important is the fact that the selection of the participants (now better
described) gives ample room for selection bias. I understand that this was the most feasible way to
carry out the study, but it needs to be discussed how the selection of participants might affect the
results. (Only including participants who show up to market places, places of worship etc, very likely
introduces a selection bias towards including more healthy individuals, those able to leave the home as
an  example.)  Also,  since  the  sampling  of  participants  was  not  population-based,  I disagree  with
formulations like "prevalence of GERD in Nigeria is xx %). This study design does not provide results
that can be used to estimate the national prevalence.
That said, despite the obvious shortcomings of this study mentioned above, I repeat what I said in my
first review: "There is a major gap in GERD research, with little or no population prevalence data from
the  African  continent,  especially from  the  Sub-Saharan  setting.  The  present  study is  therefore  a
welcome addition". 
Are the methods appropriate and well described?
If not, please specify what is required in your comments to the authors.
Yes
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 am able to assess the statistics
Quality of written English
Please indicate the quality of language in the manuscript:
Acceptable
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, fees, funding, or salary from an
organisation that may in any way gain or lose financially from the publication of this
manuscript, either now or in the future?
2. Do you hold any stocks or shares in an organisation that 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 relating 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 declare 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.
I agree to the open peer review policy of the journal. I understand that my name will be included on my
report to the authors and, if the manuscript is accepted for publication, my named report including any 
attachments I upload will be posted on the website along with the authors' responses. I agree for my 
report to be made available under an Open Access Creative Commons CC-BY license 
(http://creativecommons.org/licenses/by/4.0/ ). I understand that any comments which I do not wish to 
be included in my named report can be included as confidential comments to the editors, which will not
be published.
I agree to the open peer review policy of the journal
Reviewer’s report
Title: Gastroesophageal reflux disease in a typical African population A symptom-based multicenter
study.
Version: 2 Date: 24 Jul 2019
Reviewer: Helena Nordenstedt
Reviewer's report:
This manuscript has substantially improved since initial review. Most comments have been addressed
adequately and sufficiently (and in some ways even "over-addressed", as in the case of physical activity
where the reviewer/reviewer's former research group needlessly has been extensively cited). 
However, some comments have not been addressed, and I would recommend giving the authors the
chance to further improve. Most important is the fact that the selection of the participants (now better
described) gives ample room for selection bias. I understand that this was the most feasible way to
carry out the study, but it needs to be discussed how the selection of participants might affect the
results. (Only including participants who show up to market places, places of worship etc, very likely
introduces a selection bias towards including more healthy individuals, those able to leave the home as
an  example.)  Also,  since  the  sampling  of  participants  was  not  population-based,  I disagree  with
formulations like "prevalence of GERD in Nigeria is xx %). This study design does not provide results
that can be used to estimate the national prevalence.
That said, despite the obvious shortcomings of this study mentioned above, I repeat what I said in my
first review: "There is a major gap in GERD research, with little or no population prevalence data from
the  African  continent,  especially from  the  Sub-Saharan  setting.  The  present  study is  therefore  a
welcome addition". 
Are the methods appropriate and well described?
If not, please specify what is required in your comments to the authors.
Yes
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 am able to assess the statistics
Quality of written English
Please indicate the quality of language in the manuscript:
Acceptable
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, fees, funding, or salary from an
organisation that may in any way gain or lose financially from the publication of this
manuscript, either now or in the future?
2. Do you hold any stocks or shares in an organisation that 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 relating 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 declare 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.
I agree to the open peer review policy of the journal. I understand that my name will be included on my
report to the authors and, if the manuscript is accepted for publication, my named report including any 
attachments I upload will be posted on the website along with the authors' responses. I agree for my 
report to be made available under an Open Access Creative Commons CC-BY license 
(http://creativecommons.org/licenses/by/4.0/ ). I understand that any comments which I do not wish to 
be included in my named report can be included as confidential comments to the editors, which will not
be published.
I agree to the open peer review policy of the journal
Please review this paper.
user
Reviewer’s report
Title: Gastroesophageal reflux disease in a typical African population A symptom-based multicenter
study.
Version: 2 Date: 24 Jul 2019
Reviewer: Helena Nordenstedt
Reviewer's report:
This manuscript has substantially improved since initial review. Most comments have been addressed
adequately and sufficiently (and in some ways even "over-addressed", as in the case of physical activity
where the reviewer/reviewer's former research group needlessly has been extensively cited). 
However, some comments have not been addressed, and I would recommend giving the authors the
chance to further improve. Most important is the fact that the selection of the participants (now better
described) gives ample room for selection bias. I understand that this was the most feasible way to
carry out the study, but it needs to be discussed how the selection of participants might affect the
results. (Only including participants who show up to market places, places of worship etc, very likely
introduces a selection bias towards including more healthy individuals, those able to leave the home as
an  example.)  Also,  since  the  sampling  of  participants  was  not  population-based,  I disagree  with
formulations like "prevalence of GERD in Nigeria is xx %). This study design does not provide results
that can be used to estimate the national prevalence.
That said, despite the obvious shortcomings of this study mentioned above, I repeat what I said in my
first review: "There is a major gap in GERD research, with little or no population prevalence data from
the  African  continent,  especially from  the  Sub-Saharan  setting.  The  present  study is  therefore  a
welcome addition". 
Are the methods appropriate and well described?
If not, please specify what is required in your comments to the authors.
Yes
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 am able to assess the statistics
Quality of written English
Please indicate the quality of language in the manuscript:
Acceptable
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, fees, funding, or salary from an
organisation that may in any way gain or lose financially from the publication of this
manuscript, either now or in the future?
2. Do you hold any stocks or shares in an organisation that 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 relating 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 declare 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.
I agree to the open peer review policy of the journal. I understand that my name will be included on my
report to the authors and, if the manuscript is accepted for publication, my named report including any 
attachments I upload will be posted on the website along with the authors' responses. I agree for my 
report to be made available under an Open Access Creative Commons CC-BY license 
(http://creativecommons.org/licenses/by/4.0/ ). I understand that any comments which I do not wish to 
be included in my named report can be included as confidential comments to the editors, which will not
be published.
I agree to the open peer review policy of the journal
assistant