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Does soccer headgear reduce the incidence of sport-related concussion? A cluster, randomised controlled trial of adolescent athletes
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  • Published on:
    Continued Question About As-Treated Analysis
    • Zachary O. Binney, Epidemiologist Binney Research, Analytics, and Sports Services, LLC

    Dear Drs. McGuine, Hetzel, and Kliethermes,

    Thank you for your thorough response to my initial comment.

    I am wondering if you could help me understand the new AE-level as-treated analysis you have done in response to Point 2. This accounts for all non-compliant AEs among all athletes, correct? If I understood you correctly, there were somewhat more than the 711 non-compliant AEs reported in the paper and which you reported in your response to Point 4, correct?

    What would be very helpful to see is a.) the number of AEs and b.) the number of SRCs that occurred during those AEs for each of the following groups when considering any non-compliant AE, not just ones from athletes who suffered an SRC while non-compliant or were non-compliant >50% of the time:

    Assigned HG/Did Not Wear:
    Assigned HG/Did Wear:
    Assigned No HG/Did Not Wear:
    Assigned No HG/Did Wear:

    Thank you again for your thorough response.

    Conflict of Interest:
    Dr. Binney declares no competing interests relevant to the current paper. He does, however, wish to report receiving ongoing consulting fees from the pharmaceutical and laboratory clients of Epidemiology Methods and Research, LLC and a Major League Baseball team. He has also received past consulting fees from Vald Performance and the Jacksonville Jaguars National Football League team.
  • Published on:
    Response to the comments for the paper: Does soccer headgear reduce the incidence of sport-related concussion? A cluster, randomised controlled trial of adolescent athletes.
    • Timothy McGuine, Researcher University of Wisconsin School of Medicine and Public Health
    • Other Contributors:
      • Scott Hetzel, Biostatistician
      • Stephanie Kliethermes, Assistant Professor

    To: The British Journal Sports Medicine

    We are grateful for Dr. Binney’s interest in our study and his consideration of a portion of the results presented in the manuscript.

    Listed below are our responses to each of the concerns raised in the letter.

    1. In the as-treated analysis you have a very strange result. Your multivariate risk ratio (which is actually a rate ratio) is 0.63 for everyone overall, 0.64 for females, and 0.93 for males. The result for everyone should be between the results for males and females. Can you please clarify how you got these results, including the exact model(s) you used and how you calculated the rate ratios? Did you use a group*sex interaction term to get the sex-specific results?

    Response: We thank you for noticing the mathematical inconsistency in Table 4 rate ratio results for the as-treated analyses. You are correct that if these results were from one model, the overall rate ratio estimate would need to be in-between the male/female estimates. We should note that these were actually 3 separate mixed-effects models: (1) the overall model adjusting for all variables including sex, (2) female sub-group model adjusting for all variables –excluding sex, and (3) male sub-group model adjusting for all variables –excluding sex. We apologize that the footnote in the table is unclear in this regard. We did attempt to use interaction models for this analyses, but did not achieve consistent convergence. As such, we opt...

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    Conflict of Interest:
    All contributors to this response are members of the author team for the paper: Does soccer headgear reduce the incidence of sport-related concussion? A cluster, randomised controlled trial of adolescent athletes. Br J Sports Med. 2019 May 14. pii: bjsports-2018-100238. doi: 10.1136/bjsports-2018-100238.
  • Published on:
    Concerns About As-Treated Analysis
    • Zachary O. Binney, Epidemiologist Binney Research, Analytics, and Sports Services, LLC

    Dear Dr. McGuine et al,

    I'd like to commend you on running a large RCT on such an important topic (assessing the purported effectiveness of concussion-reduction technologies). Unfortunately I have some concerns about some aspects of your data and analysis, particularly the as-treated analysis in Table 4and your reported adherence numbers. I am hoping you can clarify these concerns and re-do parts of your analysis.

    1. In the as-treated analysis you have a very strange result. Your multivariate risk ratio (which is actually a rate ratio) is 0.63 for everyone overall, 0.64 for females, and 0.93 for males. The result for everyone should be between the results for males and females. Can you please clarify how you got these results, including the exact model(s) you used and how you calculated the rate ratios? Did you use a group*sex interaction term to get the sex-specific results?

    2. How you defined the as-treated group is concerning. You state that you only re-classified a subject if they spent >50% of their time in their non-assigned group OR if they were concussed while in their non-assigned group. This approach will bias the results of your as-treated analysis as you are deliberately misclassifying the AEs of people who do not get hurt and the non-concussed AEs of those who do. You need to classify every AE, rather than each athlete, as headgear or no headgear and repeat the as-treated analysis. Otherwise this analysis is highly questionable and...

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    Conflict of Interest:
    Dr. Binney declares no competing interests relevant to the current paper. He does, however, wish to report receiving ongoing consulting fees from the pharmaceutical and laboratory clients of Epidemiology Methods and Research, LLC and a Major League Baseball team. He has also received past consulting fees from Vald Performance and the Jacksonville Jaguars National Football League team.