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Wiebe DJ, D’Alonzo BA, Harris R, Putukian M, Campbell-McGovern C. Association Between the Experimental Kickoff Rule and Concussion Rates in Ivy League Football. JAMA. 2018;320(19):2035–2036. doi:10.1001/jama.2018.14165
The kickoff return in football, in which athletes run at speed toward each other over a long distance with the potential for significant impacts, has been associated with a substantial number of concussions.1 In 2015 in the Ivy League, a Division 1 conference of 8 private universities in the National Collegiate Athletic Association (NCAA), kickoffs accounted for 6% of all plays but 21% of concussions.2 In response, Ivy League football coaches recommended a rule change. In 2016, the kickoff line was moved from the 35-yd to the 40-yd line and the touchback line was moved from the 25-yd to the 20-yd line. The intention was to have more kickoffs land in the end zone and thereby reduce the likelihood the receiving player will advance the ball, thus increasing touchbacks. However, moving the touchback line to the 20-yd line could cause receivers to try to advance the ball, possibly decreasing touchbacks.
We investigated whether the experimental rule was associated with changes in the number of touchbacks and the rate of concussion in kickoffs in Ivy League football.
Each Ivy League football team has approximately 100 players and plays 10 games per season. Each team participates in the Ivy League’s concussion surveillance system, whereby at the start of each season, players are invited to participate using written informed consent.2 Participants who have a concussion are identified by athletic trainers; concussions are diagnosed by a team physician and entered into a web-based repository. Participation is 95%.
From the repository, we identified concussions occurring during regular-season in-conference games during the 5 seasons from 2013 through 2017. Each concussion was evaluated for what type of play it occurred in: kickoff, play from scrimmage, punt, or field-goal or point-after-touchdown attempt. The total number of each play type run each season was accessed from the NCAA archive.
Annual concussion rates before (2013-2015) and after (2016-2017) the 2016 rule, during kickoffs compared with the other play types (that presumably were not affected by the rule change), were analyzed using a difference-in-differences approach. Annual concussion counts were modeled by year and play type, with play counts as exposures, using maximum likelihood Poisson regression to estimate rate differences, difference-in-differences, and 95% confidence intervals. Stata MP 15 (StataCorp) was used for analysis. The University of Pennsylvania institutional review board waived review.
During 68 479 plays from 2013 through 2017, 159 concussions occurred (126 before and 33 after the rule), for an overall concussion rate of 2.3 per 1000 plays. Kickoffs resulting in touchbacks increased from a mean of 17.9% annually before the rule change to 48.0% after. The mean annual concussion rate per 1000 plays during kickoff plays was 10.93 before the rule change and 2.04 after (difference, −8.88; 95% CI, −13.68 to −4.09) (Table). For other play types, the concussion rate was 2.56 before the rule change and 1.18 after (difference, −1.38; 95% CI, −2.04 to −0.73). The difference-in-differences analysis showed that 7.51 fewer concussions (95% CI, −12.88 to −2.14) occurred for every 1000 kickoff plays after vs before the rule change.
The kickoff rule change in Ivy League football was associated with a reduction in concussions. Moving the touchback line3 and the kickoff line are debated. In 2011, the National Football League moved the kickoff line to the 35-yd line from the 30-yd line.4 One analysis concluded that this reduced kickoff play injuries overall but not head injuries,4 but the analysis was vulnerable to bias by not including a control injury rate change.
Limitations include possible bias by a rule that in 2016 eliminated full-contact hitting in practices in response to concerns about injuries generally.5 This rule likely did not differentially affect activities during different types of plays during competitions and hence would not bias this analysis. Confounding by player or game characteristics changing over time and surveillance bias are possible.
The action taken by Ivy League leadership based on epidemiologic evidence demonstrates how targeted policy changes can reduce sport-related concussion. Although these results may not generalize beyond the Ivy League, they may inform the NCAA as it considers adjusting the kickoff rules in football in all collegiate conferences.6
Accepted for Publication: August 30, 2018.
Corresponding Author: Douglas J. Wiebe, PhD, Department of Biostatistics, Epidemiology, and Informatics, Perelman School of Medicine, University of Pennsylvania, Blockley Hall, 423 Guardian Dr, Room 902, Philadelphia, PA 19104-6021 (email@example.com).
Published Online: October 1, 2018. doi:10.1001/jama.2018.14165
Author Contributions: Dr Wiebe had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Concept and design: Wiebe, Putukian, Campbell-McGovern.
Acquisition, analysis, or interpretation of data: All authors.
Drafting of the manuscript: Wiebe, D’Alonzo, Putukian, Campbell-McGovern.
Critical revision of the manuscript for important intellectual content: All authors.
Statistical analysis: Wiebe.
Obtained funding: Wiebe.
Administrative, technical, or material support: D’Alonzo, Putukian, Harris, Campbell-McGovern.
Supervision: All authors.
Conflict of Interest Disclosures: All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr Putukian is principal investigator, Dr Wiebe and Ms Campbell-McGovern are co–principal investigators, and Ms D’Alonzo is research coordinator of the Ivy League–Big Ten Epidemiology of Concussion Study. Ms Harris is the executive director of the Ivy League and Ms Campbell-McGovern is the deputy executive director of the Ivy League. No other disclosures were reported.
Funding/Support: This research was conducted as an activity of the Ivy League–Big Ten Epidemiology of Concussion Study, which is an initiative of the Big Ten–Ivy League Traumatic Brain Injury Research Collaboration. The concussion surveillance system and repository, from which the data were obtained, is funded by the Presidents of the Ivy League Universities and the Big Ten athletic conference. Dr Wiebe and Ms D’Alonzo were funded through a contract from the Ivy League and are also supported by the Penn Injury Science Center, which is funded by the Centers for Disease Control and Prevention (CDC) (Injury Control Research Center grant R49CE002474).
Role of the Funder/Sponsor: As authors, Ms Harris, director of the Ivy League, and Ms Campbell-McGovern, deputy executive director of the Ivy League, had input on the design and interpretation of the analysis. Neither the Big Ten nor the CDC had any other role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; or decision to submit the manuscript for publication.
Additional Contributions: We thank Martha Cooper, MSW, Big Ten Academic Alliance, for helpful input on drafting the manuscript and Jesse Hsu, PhD, MS, Department of Biostatistics, Wharton School, University of Pennsylvania, for guidance on statistical modeling. Neither received compensation for their contributions.