Gastrointestinal Symptoms After Sport-Related Concussion in Irish Athletes

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Finnegan E et al., investigated the study entitled “Gut-Brain Impact in Sport-Related Concussion: Prevalence and Characteristics of Post-Concussion Gastrointestinal Symptoms in Irish Athletes,” This study investigates the prevalence, severity, and persistence of gastrointestinal (GI) symptoms following sport-related concussion in Irish athletes. The topic is timely and relevant, as GI symptoms are often overlooked in concussion assessment and recovery. The authors use validated questionnaires and provide detailed symptom profiling. Overall, the study contributes useful data to the emerging gut–brain axis literature in sport-related concussion. However, improvements are needed in manuscript structure, clarity, figure, table integration, and presentation to strengthen the overall impact and readability.

1. The title is appropriate and clearly describes the study, it might benefit from being shortened to enhance clarity and readability. Authors shoul ensure consistent formatting and letter size throughout the title line no 1-4.
2. The authors should review the affiliation section to ensure that the formatting is consistent, the numbering is correct, and the presentation of institutional details is clear. In particular, it would be helpful to check and, if necessary, correct the formatting of country information (e.g., “Ireland -1”), postal codes, and the placement of email addresses at the end of the affiliations.
3. The authors should remove the numbering from the keywords section and formatting them according to the standard journal guidelines? Thank you for your attention to this detail.
4. The Introduction is overly long and contains too many references. The authors should condense it by reducing redundant paragraphs and citing only the most relevant studies.
5. It might be beneficial to include a brief explanation of how confidentiality was maintained, as this could enhance the transparency and ethical rigor of the research, especially since ethical approval number is already mentioned.
6. The methods for statistical analysis (Chi-square tests, Mann–Whitney tests) appear to be well-suited for the study. It might be beneficial to consider including additional details on effect size calculation to further strengthen the robustness of the findings.
7. Figure 1 and Figure 2 illustrate the prevalence and severity of GI symptoms. It might be helpful to consider enhancing the clarity of the labels and providing more detailed captions for these figures.
8. It seems that Figures 1 and 2 may contain some information that overlaps with what is already presented in Tables 3 and Supplementary Tables S5a/S5b. It might be helpful to consider either consolidating this information or providing a clearer justification for the inclusion of these figures.
9. It seems that Figures 1 and 2 could be more effectively integrated into the broader discussion of the gut–brain axis and clinical screening argument. The authors should consider it.
10. It might be beneficial to consider discussing the clinical relevance of the changes observed in Table 2 (Bristol Stool Scale), such as the potential implications for hydration, nutrient absorption, or athlete performance.
11. The authors should ensure that there is consistency between the main manuscript and the supplementary material? As the supplementary file does not include a reference list, it would be greatly appreciated if you could verify that all sources mentioned there are correctly cited in the main manuscript and that no references are missing or uncited.
12. the correct use of punctuation, particularly commas, full stops, and colons? This would greatly help in enhancing clarity, consistency, and grammatical accuracy.

Author Response

Response to Reviewer 1 Comments

Dear Reviewer,

Thank you for the opportunity to revise and resubmit our manuscript. We sincerely appreciate the time, effort, and constructive feedback you provided. Your comments helped us significantly strengthen the clarity, presentation, and overall rigour of the manuscript.

Please find below our detailed, point‑by‑point responses. All revisions have been incorporated into the revised manuscript and are marked below and in the PDF file attached with line numbers provided for ease of reference.

We hope that these revisions satisfactorily address all of your concerns and improve the clarity, rigour, and relevance of this work.

Kind regards,

Emma Finnegan (on behalf of all authors)

 

Date of this review [09 Feb 2026 08:42:36]

Reviewer 1 Comment 

Finnegan E et al. investigated the study entitled “Gut-Brain Impact in Sport-Related Concussion: Prevalence and Characteristics of Post-Concussion Gastrointestinal Symptoms in Irish Athletes,” This study investigates the prevalence, severity, and persistence of gastrointestinal (GI) symptoms following sport-related concussion in Irish athletes. The topic is timely and relevant, as GI symptoms are often overlooked in concussion assessment and recovery. The authors use validated questionnaires and provide detailed symptom profiling.

1. Reviewer 1 Comment: The title is appropriate and clearly describes the study, it might benefit from being shortened to enhance clarity and readability.

 

Author Response: Thank you for this helpful comment we agree and in response to your suggestion, we have shortened the title to improve clarity and readability. We have also revised the formatting to ensure consistent font style and letter size throughout the title (lines 1-4).

 

Old title:   Gut-Brain Impact in Sport-Related Concussion.

Subtitle: Prevalence and Characteristics of Post- Concussion Gastrointestinal Symptoms in Irish Athletes.

 

New title: Gastrointestinal Symptoms After Sport‑Related Concussion in Irish Athletes

 

2. Reviewer 1 Comment: The authors should review the affiliation section to ensure that the formatting is consistent, the numbering is correct, and the presentation of institutional details is clear. It would be helpful to check and, if necessary, correct the formatting of country information (e.g., “Ireland -1”), postal codes, and the placement of email addresses at the end of the affiliations.

 

Author Response: Thank you for identifying this formatting oversight we have revised the affiliation section detail and formatting to ensure consistent throughout (lines 5-12).

 

3. Reviewer 1 Comment: The authors should remove the numbering from the keywords section and format them according to the standard journal guidelines.

Author Response: Thank you for identifying this oversight we have removed keyword numbering.

 

4. Reviewer 1 Comment: Introduction is overly long and contains too many references. The authors should condense it by reducing redundant paragraphs and citing only the most relevant studies.

Author Response: Thank you, we appreciate this feedback. We have condensed the Introduction to improve clarity and focus. Redundant paragraphs were removed, speculative mechanistic detail was eliminated, and the remaining content was streamlined to provide a clearer progression from SRC background to study rationale. We also reduced the number of references, retaining only those essential and most relevant to the study aims, and standardised citation formatting throughout.

 

5. Reviewer 1 Comment: It might be beneficial to include a brief explanation of how confidentiality was maintained, as this could enhance the transparency and ethical rigor of the research, especially since ethical approval number is already mentioned.

Author Response:  - Thank you for this helpful comment. We have added a brief explanation of how confidentiality and anonymity were maintained to enhance ethical transparency.

Section 2.1.1, lines 125–130 now include the following text:

• New text: “To maintain confidentiality, no personal identifiable information (e.g., names) was collected, and all responses were stored anonymously on encrypted, password‑protected institutional cloud storage (OneDrive) accessible only to the research team.”

 

6. Reviewer 1 Comment: The methods for statistical analysis (Chi-square tests, Mann–Whitney tests) appear to be well-suited for the study. It might be beneficial to consider including additional details on effect size calculation to further strengthen the robustness of the findings.

Author Response:  - Thank you for this helpful suggestion. We have clarified and consolidated our effect size reporting within the Statistical Analysis section. Previously, effect sizes were described in separate paragraphs; these have now been merged and introduced earlier for clarity and coherence.

 

Section 2.2 (line 167) now reads: “Effect sizes were calculated using Cramér’s V for chi-square tests (χ²), rank-biserial correlations for Mann–Whitney U tests, and absolute risk differences (ARD), odds ratios (OR), and relative risks (RR) for prevalence comparisons.”

 

7. Reviewer 1 Comment: Figure 1 and Figure 2 illustrate the prevalence and severity of GI symptoms. It might be helpful to consider enhancing the clarity of the labels and providing more detailed captions for these figures.

Author Response: Thank you for this helpful comment. We have revised Figures 1 and 2 to improve clarity by retitling figure 2 and expanding both figure captions to provide more detailed descriptions of what each figure presents. These revisions will help ensure that the figures now independently communicate their role and the patterns in symptom presence and severity.

Improved captions:

Line 286: Figure 1. Presence versus absence of self‑reported gastrointestinal (GI) symptoms post‑concussion among participants.

The bar chart displays, for each of the 20 GI symptoms, the proportion of 1,920 total GI symptom ratings provided by 96 of the 106 participants who reported ≥1 GI symptom post-SRC. Of these ratings, 880 (45.8%, orange bars) indicated some level of GI disturbance (ratings 1–4), with 532 (60.5%) reported by female participants and 348 (39.5%) by male participants. The remaining 1,040 ratings (54.2%, blue bars) reflected absence of the symptom (rating = 0), following SRC; corresponding prevalence and severity distributions are described in the Results (section 3.4).

Line 299: Figure 2. Prevalence and severity distribution of self-reported gastrointestinal (GI) symptoms post-concussion among symptomatic participants (n = 96).

Severity ratings (1–4) are displayed for each of the 20 GI symptoms, with Rating 1 (“present, but no worse than usual”, blue bars), Rating 2 (“mild”, orange bars), and Ratings 3–4 (“moderate–severe”, red bars). Percentages represent the proportion of the 96 symptomatic participants endorsing each severity level for each symptom. This figure enables comparison of the frequency and severity of all GI symptoms experienced following SRC; corresponding prevalence and severity distributions are described in the Results (section 3.4.1).

8. Reviewer 1 Comment: It seems that Figures 1 and 2 may contain some information that overlaps with what is already presented in Tables 3 and Supplementary Tables S5a/S5b. It might be helpful to consider either consolidating this information or providing clearer justification for the inclusion of these figures.

Author Response: Thank you for this constructive comment. While Figures 1 and 2 draw on the same underlying data as Table 3 and Supplementary Tables S5a/S5b, they provide essential visual summaries that the tables alone cannot. Figure 1 presents overall symptom presence, and Figure 2 illustrates the distribution of severity ratings across all GI symptoms, enabling rapid visual comparison and pattern recognition. To strengthen clarity, we have revised the figure titles and captions to better communicate their purpose.

Table 3 provides an aggregated GI severity score (SSI) and does not display distributional patterns. Supplementary Tables S5a/S5b provide numerical prevalence and descriptive intensity summaries that support the text but are not intended for quick visual interpretation. Together, the tables offer precise numerical values, while the figures convey accessible visual patterns that enhance interpretation and reader comprehension. For these reasons, we believe both formats add value to this manuscript and should be retained.

9. Reviewer 1 Comment: It seems that Figures 1 and 2 could be more effectively integrated into the broader discussion of the gut–brain axis and clinical screening argument. The authors should consider it.

Author Response: Thank you for this helpful comment. We agree that Figures 1 and 2 were not sufficiently integrated into the broader interpretation of GI symptoms, gut–brain axis considerations, and implications for clinical screening.

To address this, we revised the Discussion (Sections 4.0 and 4.1) to:

• reference Figures 1–2 when describing symptom frequency and severity;
• integrate the findings into a cautious discussion of potential gut–brain axis relevance; and
• strengthen the rationale for brief GI‑symptom checks within concussion screening tools.

Please see lines 500, 515, 524-528.

 

10. Reviewer 1 Comment: It might be beneficial to consider discussing the clinical relevance of the changes observed in Table 2 (Bristol Stool Scale), such as the potential implications for hydration, nutrient absorption, or athlete performance.

Author Response: Thank you for this helpful suggestion. We have expanded Section 4.0 to provide cautious clinical context for the changes observed in Table 2 (see lines 503, 514, 540, and 616 in the revised manuscript). We note that the small absolute reduction in stool frequency is unlikely to be clinically meaningful at the group level; however, the variability in bowel habits may be relevant in individual cases and may warrant simple monitoring approaches (e.g., stool‑form diaries) in athletes with ongoing GI symptoms. These additions address hydration, intake tolerance, and practical considerations without inferring unmeasured mechanisms or performance effects.

Please see section 4.0, lines 503; 514 and 540; 616.

 

11. Reviewer 1 Comment: The authors should ensure that there is consistency between the main manuscript and the supplementary material.

Author Response: Thank you for this comment. We completed a full cross‑check to ensure consistent terminology, table/figure cross‑references, variable definitions, and abbreviations across the main manuscript and supplementary material. Wording and labels were amended where necessary so that all supplementary references align with those in the main manuscript.

 

12. Reviewer 1 Comment: As the supplementary file does not include a reference list, it would be greatly appreciated if you could verify that all sources mentioned there are correctly cited in the main manuscript and that no references are missing or uncited.

Author Response: Thank you for highlighting this. We verified that all citations appearing in the supplementary material correspond to the main manuscript’s reference list.

 

13. Reviewer 1 Comment: the correct use of punctuation, particularly commas, full stops, and colons?

Author Response: Thank you for this helpful comment. We conducted a manuscript‑wide punctuation and language review and corrected comma usage, full stops, colons, and other formatting inconsistencies throughout.

 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This work addresses an important and timely gap: gastrointestinal symptoms after sport-related concussion (SRC).

It is unclear whether respondents reported symptoms related to their most recent concussion, worst concussion, or any concussion.

The study is an online, retrospective, self-report survey with an extremely wide time-since-injury window (0.03–216 months). This design is highly susceptible to recall bias, selection bias, and misclassification of concussion and symptom timing.

Persistent symptoms beyond recovery” is not interpretable without a definition of “recovery” (self-perceived, clinical clearance, return-to-play, symptom-free period). In a retrospective survey, “persistence” is especially vulnerable to inconsistent interpretation.

The Background asserts GI symptoms may impair digestion, nutrient absorption, and energy availability. These mechanisms are plausible but not measured here. The Conclusions then move toward recommendations for protocol integration. With the present design, the appropriate inference is descriptive (prevalence of self-reported symptoms), not mechanistic or practice-changing.

You state timepoint differences were examined, but do not specify how timepoints were defined or binned, nor the sample size per bin. Given the large range (days to 18 years), timepoint comparisons are likely unstable and potentially misleading without careful stratification and sensitivity analyses.

Potential confounders (diet changes, travel, medications such as NSAIDs, stress/anxiety, pre-existing GI conditions, menstrual cycle effects, IBS) are not acknowledged; these could strongly influence GI symptom reporting.

The sample is convenience-based and self-selected; therefore, claims implying broad applicability “across all levels of play in Ireland” should be tempered. The data support “among respondents,” not national-level inference.

 

 

Author Response

Dear Reviewer,

Thank you for the opportunity to revise and resubmit our manuscript. We sincerely appreciate the time, effort, and constructive feedback you provided. Your comments have helped us strengthen the clarity, presentation, and overall rigour of the manuscript.

In the attached PDF, you will find a point‑by‑point response in which we address each comment in detail and outline the revisions made to clarify the study design, improve methodological transparency, and temper interpretation in line with the descriptive nature of the data. All revisions are incorporated into the revised manuscript, with line numbers provided for ease of reference.

We hope that these revisions satisfactorily address your concerns and further improve the clarity, rigour, and relevance of this work.

Kind regards,
Emma Finnegan (on behalf of all authors)

 

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have addressed all previous comments in the revised manuscript, and the revised manuscript is now suitable for publication

Reviewer 2 Report

Comments and Suggestions for Authors

This version of the article shows a significant improvement, as evidenced by more fluid writing, with some less dense and more explicit details. It is therefore publishable