PONE-D-21-29503

Seasickness among Icelandic seamen

PLOS ONE

Dear Dr. Arnardottir,

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.

Thank you for submitting a promising and interesting manuscript about seasickness to PLOS ONE. Since the three reviewers had some fundamental suggestions for improvement, I have allocated two months for you to adjust your manuscript accordingly. If you disagree with some suggestions, please respond in detail in your rebuttal document. Should you submit a revised manuscript earlier, then I will respond when you resubmit.

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Andreas C. Bryhn

Academic Editor

PLOS ONE

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Partly

Reviewer #2: Partly

Reviewer #3: Partly

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2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: No

Reviewer #2: No

Reviewer #3: No

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3. Have the authors made all data underlying the findings in their manuscript fully available?

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Reviewer #1: No

Reviewer #2: No

Reviewer #3: No

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4. Is the manuscript presented in an intelligible fashion and written in standard English?

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Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

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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: 1. The research is a simple questionnaire based cross-sectional study whose conclusions are based on responses to a 90-question questionnaire of subjects who have volunteered to participate in the project. Thus, assessment may be considered subjective depending on the state of mind and condition of individuals who have consented to provide data. To bring in objectivity, the study could have included physical examination of subjects as well as covered the assessed conclusions by validating data over a period of time.

2. The questionnaire used has not been published along with the manuscript for the reviewer to objectively assess the interpretation of data. Also, the questionnaire has been validated not by a pilot study but by the mere improvement of an already existing questionnaire which was used in earlier research. Thus, objective validation of the questionnaire needs to be done along with a prior pilot assessment of a fixed number of subjects before undertaking the actual research. The technical soundness of the research may not be possible to comment upon since the questionnaire is not available at the present period.

3. Although cross-sectional in nature, lack of controls in the study renders the comparative analysis of data impossible.

4. Conclusions drawn based on the data collated reflects earlier studies in the same arena, with only a few aspects coming out as unique in the current study.

5. Increased risk of accidents due to Mal de Debarquement within first four days after coming ashore (as declared by the authors) requires corroboration and statistical evidence which is not brought out in the current paper.

6. Objective assessment of tension headache and tinnitus has not been done in the study and is totally based on patient description which may lead to erroneous conclusions bringing in subjectivity to the research.

7. Having included women in the study may lead to errors in assessment, and separate criteria for assessment could have been included for women and a descriptive data analysis of impact of being at sea for women needs to be furnished. A comparative data analysis between men and women who have been at sea for the same period of time with constants of type of vessel, age profile and experience at sea may throw more light on the impact of seasickness among Icelandic ‘sea-persons’.

8. Lines 229 to 232 are contradictory in nature. It’s a known fact that tinnitus is more common under age 50 while hearing loss is common in seamen over 50 years of age. However, the authors state the opposite. This needs to be addressed.

9. The study concludes a higher proportion of subjects having migraine compared to a European study, however, the nature of the cited European study is obscure, viz., sample size, type of study, controls etc. Thus, this comparison is fallacious till such time both the current and European studies have been done under similar if not exact circumstances.

10. The study purports in line 160-161 that those who were out at sea for a week or less were more likely to experience seasickness symptoms than those who were out for more than a week (p=0.009) however a contrary statement is made in line 164-167 that both tinnitus and hearing loss appear to increase in accord with length of sea journey, although no significant difference was found (p>0.05). Nor was any significant difference found between length of sea journey and seasickness-related symptoms (p>0.05). This needs deliberation.

11. The data analysis does support the conclusion that seasickness and seasickness like symptoms along with migraine, tinnitus and tension headache are all common features in individuals who venture at sea. However, nothing new has emerged out of this questionnaire-based study except for the fact that further research needs to be done to corroborate various evidence of accidents ashore, types and sizes of vessels, duration of sea, gender differences, age variations among other factors to validate the correlation between trysts at sea with sea sickness.

12. Statistical analysis is basic with use of SPSS ver 25. It would be prudent to bring out correlational study graphs, pie charts and a comprehensive correlational analysis to establish the soundness of the questionnaire. Further, results of Chi Square, Phi and Cramer’s V coefficient may be brought out in detail to solidify the statistical claims. Although the statistical analysis has been performed appropriately, the reviewer needs to be presented with detailed results.

13. Authors have not made all the data underlying the findings available in the manuscript. Questionnaire is not attached and pilot survey if conducted is not described.

Reviewer #2: This paper successfully conducted a questionnaire survey on 262 of the 376 male crew members, and investigated their age, BMI, disease history, seasickness, etc., to understand the working environment and current situation of Icelandic crew members, which has certain research significance, but there are also some shortcomings. :

1. This article is not innovative enough.

2.The reliability of the questionnaire is not high, the subjective factors are mixed, and the individual assessment is inaccurate.

3. 30% of citations are from 10 years ago, which is relatively old.

4. The picture is not clear and the figure lenged is missing.

5. The citation format of literature 32,39 is different from other literatures.

Reviewer #3: The present manuscript describes the results of a survey that was done among Icelandic seamen with regards to their level of seasickness, health-related factors, and their work environment. More than 260 people completed the survey and offered an interesting insight into the effect of seasickness among this group. The rationale of the study is clear and the procedure sound. However, I have some concerns regarding the presentation of the methods and results that need to be addressed by the authors.

Major concerns:

1. Methods: The structure of the questionnaire and the inquired items remain unclear. The authos say that “Questions were asked about working conditions at sea, history of seasickness (seasickness, mal de debarquement and seasickness symptoms), health, demographic background variables…” (p6). This is not enough detail to really understand what was measured in this survey and how it was structured. As this is the main component of the study, the questionnaire needs to be described with mor details. For instance, what is the difference between seasickness and seasickness symptoms? What was the scale to measure seasickness, simply binary “yes/no” or with more details such as “never/sometimes/often”? What do health measures include and why were these items specifically chosen? In addition to describing the main components of the questionnaire, the authors could consider adding the full questionnaire as additional material to the manuscript.

2. Results:

a. The objective of the study was to “…explore the impact of seasickness and mal de debarquement on seamen’s health…” (p5). This makes sense, but the way this objective was tackled in the results section does not really address this objective. The authors chose to run a large number of chi-squared tests to compare different groups, but these tests simply compare different groups (sometimes based on age, sometimes based on experience, sometimes based on position on the vessel etc.). There is no clear rationale offered why these groups were compared (except for age). In order to explore the impact of seasickness on health, it seems more logical to run regression analysis with sickness measures (and other factors such as age, duration on sea etc.) as predictive factors and health-related factors as outcome variables.

b. Only p-values are provided as statistical outcome. This is not sufficient; full statistics (degrees of freedom, effect size) should be included as well in order to better understand how meaningful these group differences are. With a large sample size, even small effects will become significant, but this does not mean that these differences are meaningful.

c. The authors mention that correlations were performed between the groups. I cannot find a summary of these correlations in the manuscript, except for the ones that were explicitly mentioned. I would prefer to see a summary of the correlations, even if they failed significance. Also, why were more common correlation coefficients such as Spearman correlations not used?

d. The survey offers a lot of information. However, the results are not very well structured in the manuscript; instead, the authors list a lot of findings and p-values for a variety of group comparisons (see comment above). I suggest to structure these findings more clearly and present them in subsections that address each factor of interest separately (e.g., seasickness symptoms, health etc.).

e. The figures should be optimized. At least, the SD or Sem should be included. More recently, it has become more common to present the data in a more informative way that indicates the variability and/or shows the individual data points (violin plots, box plots). A bar graph with no further information only provides little information.

Other comments:

1. What was the exact number of male and female seamen in the survey?

2. With regards to terminology, is there a more gender-neutral term instead of seamen (this is not my area of expertise, just wondering). According to a quick google search is seems that some countries (e.g., Canada) have decided to drop the term seamen and now generally refer to them as sailors to be more gender inclusive. Might be worth considering.

3. A large number of tests between two groups were calculated, where the p values adjusted accordingly?

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Reviewer #1: No

Reviewer #2: No

Reviewer #3: No

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Attachments

Attachment

Submitted filename: PONE_review_renu.docx

PONE-D-21-29503R1Seasickness among Icelandic seamenPLOS ONE

Dear Dr. Arnardottir,

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.

==============================

ACADEMIC EDITOR: Dear authors, Thank you for submitting an improved manuscript with great potential. However, according to this journal's publication criteria, all manuscripts must have perfect English before acceptance. I have detected several spelling and grammar errors in the current version. Please have it proof-read by a native English speaker before resubmission.

==============================

Please submit your revised manuscript by September 15. 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. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

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If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: https://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols. Additionally, PLOS ONE offers an option for publishing peer-reviewed Lab Protocol articles, which describe protocols hosted on protocols.io. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols.

We look forward to receiving your revised manuscript.

Kind regards,

Andreas C. Bryhn

Academic Editor

PLOS ONE

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Please review your reference list to ensure that it is complete and correct. If you have cited papers that have been retracted, please include the rationale for doing so in the manuscript text, or remove these references and replace them with relevant current references. Any changes to the reference list should be mentioned in the rebuttal letter that accompanies your revised manuscript. If you need to cite a retracted article, indicate the article’s retracted status in the References list and also include a citation and full reference for the retraction notice.

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Seasickness among Icelandic seamen

PONE-D-21-29503R2

Dear Dr. Arnardottir,

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.

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Andreas C. Bryhn

Academic Editor

PLOS ONE

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