Impact of childhood traumatic brain injury on fitness for service class, length of service period, and cognitive performance during military service in Finland from 1998 to 2018: A retrospective register-based nationwide cohort study

Julius Möttönen; Ville T. Ponkilainen; Ville M. Mattila; Ilari Kuitunen

doi:10.1371/journal.pone.0303851

Peer Review History

Original SubmissionDecember 20, 2023
17 Mar 2024 Decision Letter - Sreeram V. Ramagopalan, Editor PONE-D-23-42327Impact of childhood traumatic brain injury on fitness for service class, length of service period, and cognitive performance during military service in Finland from 1998 to 2018: A retrospective register-based nationwide cohort study.PLOS ONE Dear Dr. Möttönen, Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process. Please submit your revised manuscript by May 01 2024 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. 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Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here. Reviewer #1: Yes ****** 5. Review Comments to the Author Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters) Reviewer #1: Dear Editor, The article by Mottonen et al report results from a data linkage study of healthcare records with military service records for individuals who as children suffered a traumatic brain injury (pTBI) compared to children who suffered arm or leg fractures. I was uncertain why this research is needed. I would also suggest more clarity on the criteria, timelines and order in which tests are given, and individuals are assessed for service. I got the impression that individuals with pTBI shouldn’t be serving at all according to guidelines but nonetheless some do. This can potentially introduce bias into the sample. A more robust discussion on the potential biases is needed. Detailed comments: 1) It is not clear why this research is needed. How will it impact future fit for service guidelines or medical recommendations for paediatric patients with these injuries? 2) Please be clear in the methods - if conscription guidelines explicitly exclude people with pTBI. 3) The discussion states: “there are numerous post-injury disorders and emotional disorders that are acceptable reasons for conscripts to receive an exemption from conscription or military service” later it goes on to say “ major operations are part of the exclusion criteria in the military handbook” Does this mean that recruits lie or are unaware of their past TBI history / major operation as a child? Does this bias the sample who make it into the service and who will eventually finish service? Is the research trying to elucidate this? 4) Please include a table with the OR – I would suggest adding them to Table 1 and Table 2 respectively. 5) I note there was no matching between groups, but the number of females was surprisingly similar in both groups. Can the authors comment on incidence rates of TBI being similar to those of fractures? It is possible that randomly the groups are the same size, but it just really jumped out at me. 6) Age is identified in Figure 1 as the main (only) confounder of the association, but it is not adjusted for in the logistic regression. Please provide rationale. 7) What is the sample size for the cognitive impairment test – if it is given 6-8 weeks after enrolment and the authors suggest some people might drop out by then ; the sample size might be smaller for this analysis. 8) I think it would be valuable to present b-test score by length of service –larger differences between groups might be observed. 9) What difference in the b-test score would be clinically meaningful? Or in the military what cut off are used to determine final posting. Abstract: 1) Reference category includes a range of lower limb fractures wider than just ankle and wrist. ****** 6. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files. If you choose “no”, your identity will remain anonymous but your review may still be made public. Do you want your identity to be public for this peer review? 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Please note that Supporting Information files do not need this step. https://doi.org/10.1371/journal.pone.0303851.r001
Revision 1
22 Apr 2024 Author Response DETAILED COMMENTS: 1) It is not clear why this research is needed. How will it impact future fit for service guidelines or medical recommendations for paediatric patients with these injuries? Author response: Thank you for this comment. We agree that this information was missing. We have now assessed this thoroughly in the manuscript. Please see, Introduction: Paragraph 4. and Discussion: Paragraph 5. 2) Please be clear in the methods - if conscription guidelines explicitly exclude people with pTBI. Author response: The reviewer 1 is correct. The Methods lacked detailed information how the service class is determined. We have now added paragraph to explain the reasoning behind the classification Simply, any form of a TBI is not an automatic exclusion from the service, everyone and every case is evaluated individually. Please, see Methods: Paragraph 4 and Discussion: Paragraph 4. 3) The discussion states: “there are numerous post-injury disorders and emotional disorders that are acceptable reasons for conscripts to receive an exemption from conscription or military service” later it goes on to say, “major operations are part of the exclusion criteria in the military handbook” Does this mean that recruits lie or are unaware of their past TBI history / major operation as a child? Does this bias the sample who make it into the service and who will eventually finish service? Is the research trying to elucidate this? Author response: Thank you for this comment. Please, see above. We have explained the exclusion criteria in a more detailed fashion. 4) Please include a table with the OR – I would suggest adding them to Table 1 and Table 2 respectively. Author response: We have now added all the ORs to tables as suggested. For the tables to be as clear as possible, we have created a new table for ORs regarding service length (Table 3). Previous Table 3 has now been moved to be Table 4 Please, see Results: Table 1, 3 and 4. 5) I note there was no matching between groups, but the number of females was surprisingly similar in both groups. Can the authors comment on incidence rates of TBI being similar to those of fractures? It is possible that randomly the groups are the same size, but it just really jumped out at me. Author response: Thank you for pointing this out. We were surprised as well. It is completely coincidental that the groups were almost exactly same size. 6) Age is identified in Figure 1 as the main (only) confounder of the association, but it is not adjusted for in the logistic regression. Please provide rationale. Author response: Thank you for this comment. It was indented to run all analyses with age adjustment. This statement has now been added to the Methods section. We also checked the logistic regression analyses and simply by honest mistake there were few analyses done without age adjustment. New analyses were performed, and results are now updated entirely regarding the ORs. There were only minor differences, and this error did not affect the final interpretation of the results. Please, see Methods: Paragraph 6, Results: Tables 1 and 3. 7) What is the sample size for the cognitive impairment test – if it is given 6-8 weeks after enrolment and the authors suggest some people might drop out by then ; the sample size might be smaller for this analysis. Author response: We agree with the Reviewer. Sample size has now been added to Table 1 and Results. Indeed, there were some individuals who completed military service, but had missing data from the cognitive b-test. We have added this as limitation. Please, see Results: Paragraph 5 and Table 1, Discussion: Paragraph 6. 8) I think it would be valuable to present b-test score by length of service –larger differences between groups might be observed. Author response: As you can see from the table below, conscripts with longer service length have better results in this test. Differences between groups are not larger. The test is done before anyone knows how long they will be serving and logically people with better test results will be selected more often to the longer service periods. This is why we chose to report the results in one group. The fact that pTBI group has lower average score is the most important independent factor and the effects are seen in the service length between groups. In addition, we have now calculated P-values for the b-test results using Welch two sample t-test. Please, see Results: Table 1. Length of service pTBI group Reference group Difference pTBI group Reference group Difference Men Men Women Women 6 months 4.28 4.40 0.12 CI 0.05-0.20 5.50 5.43 0.07 CI -2.36-2.50 9 months 4.68 4.81 0.12 CI -0.00-0.25 4.74 4.48 0.25 CI -1.19-0.68 12 months 5.34 5.50 0.16 CI 0.09-0.23 5.31 5.60 0.29 CI -0.21-0.80 All 4.47 4.89 0.15 CI 0.10-0.20 5.17 5.29 0.12 CI -0.28-0.52 9) What difference in the b-test score would be clinically meaningful? Or in the military what cut off are used to determine final posting. Author response: B-test scores from 0 to 3 usually indicate rejection from more demanding 9 to 12-month duties. Please, see Methods: Paragraph 5. ABSTRACT: 1) Reference category includes a range of lower limb fractures wider than just ankle and wrist. Author response: It is true. There also were shin fractures and fractures of patella. We have corrected this in the manuscript. Please, see Abstract: Paragraph 2 and Methods: Paragraph 2. Attachments Attachment Submitted filename: Response to reviewers.docx https://doi.org/10.1371/journal.pone.0303851.r002
2 May 2024 Decision Letter - Sreeram V. Ramagopalan, Editor Impact of childhood traumatic brain injury on fitness for service class, length of service period, and cognitive performance during military service in Finland from 1998 to 2018: A retrospective register-based nationwide cohort study. PONE-D-23-42327R1 Dear Dr. Möttönen, We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements. Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication. An invoice will be generated when your article is formally accepted. Please note, if your institution has a publishing partnership with PLOS and your article meets the relevant criteria, all or part of your publication costs will be covered. Please make sure your user information is up-to-date by logging into Editorial Manager at Editorial Manager® and clicking the ‘Update My Information' link at the top of the page. If you have any questions relating to publication charges, please contact our Author Billing department directly at authorbilling@plos.org. If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org. Kind regards, Sreeram V. Ramagopalan Academic Editor PLOS ONE Additional Editor Comments (optional): Reviewers' comments: https://doi.org/10.1371/journal.pone.0303851.r003
Formally Accepted
7 May 2024 Acceptance Letter - Sreeram V. Ramagopalan, Editor PONE-D-23-42327R1 PLOS ONE Dear Dr. Möttönen, I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now being handed over to our production team. At this stage, our production department will prepare your paper for publication. This includes ensuring the following: * All references, tables, and figures are properly cited * All relevant supporting information is included in the manuscript submission, * There are no issues that prevent the paper from being properly typeset If revisions are needed, the production department will contact you directly to resolve them. If no revisions are needed, you will receive an email when the publication date has been set. At this time, we do not offer pre-publication proofs to authors during production of the accepted work. Please keep in mind that we are working through a large volume of accepted articles, so please give us a few weeks to review your paper and let you know the next and final steps. Lastly, if your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org. If we can help with anything else, please email us at customercare@plos.org. Thank you for submitting your work to PLOS ONE and supporting open access. Kind regards, PLOS ONE Editorial Office Staff on behalf of Dr. Sreeram V. Ramagopalan Academic Editor PLOS ONE https://doi.org/10.1371/journal.pone.0303851.r004

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