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Mouthguard use in youth ice hockey and the risk of concussion: nested case–control study of 315 cases
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  • Published on:
    Response to: “Potentially Biased Results on Mouthguard Use and Reduction of Concussion Risk”
    • Brent E. Hagel, Professor Departments of Paediatrics and Community Health Sciences, Cumming School of Medicine, University of Calgary, Canada
    • Other Contributors:
      • Carolyn A. Emery, Professor
      • Luz Palacios-Derflingher, Senior Research Associate, Biostatistician
      • Kathryn J. Schneider, Associate Professor
      • Amanda M. Black, Assistant Professor
      • Paul H. Eliason, PhD Candidate
      • Dirk A. Chisholm, Medical Student

    We read with interest, and concern, the letter submitted by Schilaty et al arguing bias in our analysis examining the association between concussion and mouthguard use. Schilaty et al argue that a nested case-control study was not optimal and that “Based on a relatively small cohort, a complete case-control study would have been more appropriate than a nested case-control study.” They then go on to argue that “selection criteria of the non-concussion group biased the study as a random sample was not selected from the remaining cohort (n=2,040)” eliminating “from the analysis all non-injured players who wore mouthguards.” Finally, Schilaty et al contend that our study did not “properly compare the incidence of concussion between wearers or non-wearers of mouthguards.” There are multiple concerning statements and assertions made by the authors of the letter, Schilaty et al., that we will address below.

    Shilaty et al discuss the desire to compare “incidence of concussion between wearers and non-wearers of mouthguards.” Incidence cannot truly be estimated from a case-control study, given that the number of cases and controls is fixed from the design. Rather, we are after the odds ratio based on the ratio of the odds of exposure in cases relative to controls (the odds ratio of exposure is mathematically the same as the odds ratio of being a case). Modern conceptualizations of the case-control study invoke the idea of pseudo frequencies or quasi-rates related to construc...

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    Conflict of Interest:
    None declared.
  • Published on:
    Potentially Biased Results on Mouthguard Use and Reduction of Concussion Risk
    • Nathan D Schilaty, Assistant Professor of Physiology; Physical Medicine & Rehabilitation Mayo Clinic
    • Other Contributors:
      • Nathaniel A Bates, Assistant Professor of Biomedical Engineering
      • Aynsley M Smith, Associate Professor of Orthopedics; Physical Medicine & Rehabilitation
      • Michael J Stuart, Orthopedic Surgeon; Professor of Orthopedics

    We read the referenced article by Chisholm et al.1 with keen interest. Concussions present a significant injury burden on the athletic community, especially among youth athletes who are more susceptible to potential long-term consequences.3,7,9 Concussion diagnosis and treatment are important, but prevention is key. Chisholm and colleagues present data on young athletes that supports a reduction in the risk of concussion with the use of a mouthguard. However, the authors admit that the current literature on mouthguards has methodological limitations and high risk of bias. The primary objective of their study was to examine the association between concussion and mouthguard use in youth ice hockey.

    We agree with the benefit players derive from wearing mouthguards to protect dentition and possibly reduce the incidence and/or severity of concussion during contact sports. However, we question the statistical methodology performed and the resultant conclusions of the manuscript. The authors utilized a nested case-control design to determine the risk of concussion with mouthguard use. Due to this design utilization, the results potentially present a high risk of bias that the authors were attempting to avoid. A nested case-control design compares incident cases nested in a cohort study with controls drawn at random from the rest of the cohort.2,6 Further, a nested case-control is useful for summarizing the trends observed in a large population when study of the e...

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    Conflict of Interest:
    None declared.