Reviewer ’s report  
 
Title: Global research trends in microbiome -gut-brain axis during 2009 -2018: a bibliometric and 
visualized study  
 
Version: 0 Date: 21 Jun 2019  
 
Reviewer: Cas Swarte  
Reviewer's report:  
Why did the author s chose for the Scopus database? I would strongly advice to extend the 
research to databases such as Pubmed and Psychinfo to get a true overview of the global activity 
of MGBA research. For example 'microbiome' in Pubmed results in 56195 hits whereas the 
authors report 24369 hits on scopus regarding 'microbiome'. Furthermore, why is the year 2018 
not included in the analysis?  
Regarding figure 1: Figure 1 is biased because the authors included both no. of articles regarding 
gut microbiota and microbiota gu t brain axis (MGBA) in one figure. It can be interpreted from 
this graph that the work in MGBA surpasses the work on gut microbiota alone because the red 
line crosses the blue line. I would advise the authors to include two separate figures.  
Regarding fi gure 2: No legend is included in the figure but only in the results section. 
Furthermore, cluster 1 regards ''gut microbiota in animal models''. Are these animal models 
regarding MGBA or only gut microbiota? It is unclear to the reader how the ''cluster an alysis'' 
was performed. Furthermore, could the authors include an order of magnitude for the diameter  
Regarding figure 3: There are dots in the plot without a countrycode attached. Furthermore, 
could the authors include an order of magnitude for the diam eter. 
Regarding figure 4: There are dots in the plot without an author attached. Furthermore, could the 
authors include an order of magnitude for the diameter  
''There were statistically significant strong positive correlations 16 (r = 0.991, p <0.001) between 
the number of publications related to MGBA and the 17 number of publications related to 
microbiome in all fields over time.'' It is unclear to the reader h ow MGBA research is correlated 
to ''publications related microbiome in all fields''. Furthermore, the authors conclude through this 
correlation that ''research output related to MGBA have followed the general progress in 
scientific research production rela ted to the microbiome field''. What is the general progress in 
scientific research that the authors describe here? And why does MGBA follows this progress?  
''Research output related to MGBA most often originated from the United States. This finding 
was s imilar to other bibliometric studies in different fields.'' Ref. 29 is about ''glyphosate 
intoxication'' not about MGBA. Therefore, this conclusion is invalid.  
'' In 2013 the USA launched a special research project on gut microbiota -brain 12 axis [86].''  
Why did this review led to ''gradually become the focus of neuroscience''.  
''A bibliometric analysis applies quantitative methods'' do the authors mean qualitative?  
'' Despite these limitations, we still consider that the result of this bibliometric ana lysis a is the 
first one and is sufficient to represent the accurate situation of microbiota -gut-brain axis 
publications at global level'' I think the approach is not accurate because only the Scopus was 
included.  
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.  
 
Unable to assess  
 
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 r ecommended, please specify what aspects require further 
assessment in your comments to the editors.  
 
Not relevant to this manuscript  
 
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, fees, funding, or salary from an 
organisation that may in any way gain or lose financia lly 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 o r 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 yo u 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 unde r 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: Global research trends in microbiome -gut-brain axis during 2009 -2018: a bibliometric and 
visualized study  
 
Version: 0 Date: 21 Jun 2019  
 
Reviewer: Cas Swarte  
Reviewer's report:  
Why did the author s chose for the Scopus database? I would strongly advice to extend the 
research to databases such as Pubmed and Psychinfo to get a true overview of the global activity 
of MGBA research. For example 'microbiome' in Pubmed results in 56195 hits whereas the 
authors report 24369 hits on scopus regarding 'microbiome'. Furthermore, why is the year 2018 
not included in the analysis?  
Regarding figure 1: Figure 1 is biased because the authors included both no. of articles regarding 
gut microbiota and microbiota gu t brain axis (MGBA) in one figure. It can be interpreted from 
this graph that the work in MGBA surpasses the work on gut microbiota alone because the red 
line crosses the blue line. I would advise the authors to include two separate figures.  
Regarding fi gure 2: No legend is included in the figure but only in the results section. 
Furthermore, cluster 1 regards ''gut microbiota in animal models''. Are these animal models 
regarding MGBA or only gut microbiota? It is unclear to the reader how the ''cluster an alysis'' 
was performed. Furthermore, could the authors include an order of magnitude for the diameter  
Regarding figure 3: There are dots in the plot without a countrycode attached. Furthermore, 
could the authors include an order of magnitude for the diam eter. 
Regarding figure 4: There are dots in the plot without an author attached. Furthermore, could the 
authors include an order of magnitude for the diameter  
''There were statistically significant strong positive correlations 16 (r = 0.991, p <0.001) between 
the number of publications related to MGBA and the 17 number of publications related to 
microbiome in all fields over time.'' It is unclear to the reader h ow MGBA research is correlated 
to ''publications related microbiome in all fields''. Furthermore, the authors conclude through this 
correlation that ''research output related to MGBA have followed the general progress in 
scientific research production rela ted to the microbiome field''. What is the general progress in 
scientific research that the authors describe here? And why does MGBA follows this progress?  
''Research output related to MGBA most often originated from the United States. This finding 
was s imilar to other bibliometric studies in different fields.'' Ref. 29 is about ''glyphosate 
intoxication'' not about MGBA. Therefore, this conclusion is invalid.  
'' In 2013 the USA launched a special research project on gut microbiota -brain 12 axis [86].''  
Why did this review led to ''gradually become the focus of neuroscience''.  
''A bibliometric analysis applies quantitative methods'' do the authors mean qualitative?  
'' Despite these limitations, we still consider that the result of this bibliometric ana lysis a is the 
first one and is sufficient to represent the accurate situation of microbiota -gut-brain axis 
publications at global level'' I think the approach is not accurate because only the Scopus was 
included.  
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.  
 
Unable to assess  
 
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 r ecommended, please specify what aspects require further 
assessment in your comments to the editors.  
 
Not relevant to this manuscript  
 
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, fees, funding, or salary from an 
organisation that may in any way gain or lose financia lly 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 o r 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 yo u 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 unde r 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: Global research trends in microbiome -gut-brain axis during 2009 -2018: a bibliometric and 
visualized study  
 
Version: 0 Date: 21 Jun 2019  
 
Reviewer: Cas Swarte  
Reviewer's report:  
Why did the author s chose for the Scopus database? I would strongly advice to extend the 
research to databases such as Pubmed and Psychinfo to get a true overview of the global activity 
of MGBA research. For example 'microbiome' in Pubmed results in 56195 hits whereas the 
authors report 24369 hits on scopus regarding 'microbiome'. Furthermore, why is the year 2018 
not included in the analysis?  
Regarding figure 1: Figure 1 is biased because the authors included both no. of articles regarding 
gut microbiota and microbiota gu t brain axis (MGBA) in one figure. It can be interpreted from 
this graph that the work in MGBA surpasses the work on gut microbiota alone because the red 
line crosses the blue line. I would advise the authors to include two separate figures.  
Regarding fi gure 2: No legend is included in the figure but only in the results section. 
Furthermore, cluster 1 regards ''gut microbiota in animal models''. Are these animal models 
regarding MGBA or only gut microbiota? It is unclear to the reader how the ''cluster an alysis'' 
was performed. Furthermore, could the authors include an order of magnitude for the diameter  
Regarding figure 3: There are dots in the plot without a countrycode attached. Furthermore, 
could the authors include an order of magnitude for the diam eter. 
Regarding figure 4: There are dots in the plot without an author attached. Furthermore, could the 
authors include an order of magnitude for the diameter  
''There were statistically significant strong positive correlations 16 (r = 0.991, p <0.001) between 
the number of publications related to MGBA and the 17 number of publications related to 
microbiome in all fields over time.'' It is unclear to the reader h ow MGBA research is correlated 
to ''publications related microbiome in all fields''. Furthermore, the authors conclude through this 
correlation that ''research output related to MGBA have followed the general progress in 
scientific research production rela ted to the microbiome field''. What is the general progress in 
scientific research that the authors describe here? And why does MGBA follows this progress?  
''Research output related to MGBA most often originated from the United States. This finding 
was s imilar to other bibliometric studies in different fields.'' Ref. 29 is about ''glyphosate 
intoxication'' not about MGBA. Therefore, this conclusion is invalid.  
'' In 2013 the USA launched a special research project on gut microbiota -brain 12 axis [86].''  
Why did this review led to ''gradually become the focus of neuroscience''.  
''A bibliometric analysis applies quantitative methods'' do the authors mean qualitative?  
'' Despite these limitations, we still consider that the result of this bibliometric ana lysis a is the 
first one and is sufficient to represent the accurate situation of microbiota -gut-brain axis 
publications at global level'' I think the approach is not accurate because only the Scopus was 
included.  
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.  
 
Unable to assess  
 
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 r ecommended, please specify what aspects require further 
assessment in your comments to the editors.  
 
Not relevant to this manuscript  
 
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, fees, funding, or salary from an 
organisation that may in any way gain or lose financia lly 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 o r 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 yo u 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 unde r 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