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Abstract
Objectives Headgear use is a controversial issue in girls’ lacrosse. We compared concussion rates among high school lacrosse players in an American state with a headgear mandate (HM) to states without an HM.
Methods Participants included high schools with girls’ lacrosse programmes in the USA. Certified athletic trainers reported athlete exposure (AE) and injury data via the National Athletic Treatment, Injury and Outcomes Network during the 2019–2021 seasons. The HM cohort was inclusive of high schools from the state of Florida, which mandates the use of ASTM standard F3137 headgear, while the non-HM (NHM) cohort was inclusive of high schools in 31 states without a state-wide HM. Incidence rate ratios (IRRs) and 95% CIs were calculated.
Results 141 concussions (HM: 25; NHM: 116) and 357 225 AEs were reported (HM: 91 074 AEs; NHM: 266 151 AEs) across all games and practices for 289 total school seasons (HM: 96; NHM: 193). Overall, the concussion injury rate per 1000 AEs was higher in the NHM cohort (0.44) than the HM cohort (0.27) (IRR=1.59, 95% CI: 1.03 to 2.45). The IRR was higher for the NHM cohort during games (1.74, 95% CI: 1.00 to 3.02) but not for practices (1.42, 95% CI: 0.71 to 2.83).
Conclusions These findings suggest a statewide HM for high school girls’ lacrosse is associated with a lower concussion rate than playing in a state without an HM. Statewide mandates requiring ASTM standard F3137 headgear should be considered to reduce the risk of concussion.
- Brain Concussion
- Lacrosse
- Head Protective Devices
Data availability statement
Data may be obtained from a third party (Datalys Center, Inc.; www.datalyscenter.org) and are not publicly available.
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What are the findings?
Playing in a state with a headgear mandate (HM) meeting the ASTM F3137 standard was associated with a lower risk of experiencing a concussion injury among high school girls’ lacrosse players compared with playing in a state without a HM.
How might it impact on clinical practice in the future?
Lacrosse HMs may be warranted for use for concussion risk mitigation among high school girls’ lacrosse players.
Lacrosse headgear may be considered for concussion risk mitigation at other levels of play such as the youth or collegiate levels; further study is warranted.
Introduction
Girls’ lacrosse continues to be the fastest growing high school sport in the USA.1 Prior to the COVID-19 pandemic, high school girls’ lacrosse participation grew by 53.63% over the past decade in the USA (2008–2009: n=64 929; 2018–2019: n=99 750).1 Girls’ lacrosse is a non-contact sport; however, incidental concussions2–5 and head impacts6–8 associated with lacrosse gameplay are common. A recent epidemiological study, observed across 5 years (2008–2009 through 2013–2014) of competitive high school girls’ lacrosse, demonstrated that head/face injuries accounted for the most common game-related injuries (0.92/1000 athlete exposures (AE)), the majority of which were concussion (0.83/1000 AEs).5 Collectively, stick contact is the leading mechanism of both head impacts7 and subsequent concussions5 in high school girls’ lacrosse.
Due to the non-contact rules for girls’ lacrosse, mandated protective equipment is limited to mouthguards and eyewear.9 10 However, in response to the growing concerns regarding the mechanisms of concussion in girls’ lacrosse from incidental contact, rules allowing for the use of soft-shell headgear have been adopted as of 1 January 2017.9 Specifically, girls’ lacrosse headgear must meet the ASTM International F3137 performance standard.11 As stated in the standard, the headgear was designed ‘…to address the forces of some incidental stick and ball to headgear impacts to non-goaltending field players’.1 However, headgear effectiveness at mitigating concussion risk remains unclear.6 12 Despite this lack of clarity, in 2018, the Florida High School Athletic Association mandated the use of headgear meeting the ASTM standard headgear for lacrosse participation.
Substantial debate exists among the lacrosse community regarding implementing headgear in a non-contact sport that often exhibits incidental contact-related injury.13–16 Competing arguments have pitted the potential protective benefits of headgear (ie, decreasing severity of impacts thus reducing risk of injury) against concerns regarding risk compensation (ie, more aggressive game play behaviours) contributing to increased risk of injury.17 Originating in automobile safety research, the Peltzman effect17 posits that when safety measures (eg, headgear) are implemented, individuals compensate by increasing risk-taking behaviours.
Until now, there has been insufficient evidence regarding the effectiveness of lacrosse headgear for reducing the risk of concussion among girls’ lacrosse players to support either argument. Preliminary evidence at the high school level of girls’ lacrosse suggests that headgear may be associated with reduced head impact magnitudes6 and may not be associated with risk compensatory behaviours.18 To date, a single study of girls’ public high school lacrosse athletes in New York City has examined lacrosse headgear use, with results suggesting it is associated with lower rates of concussion during gameplay.19 We know of no published research that has examined the effect of mandated lacrosse headgear on concussion risk using a large-scale national epidemiologic approach. Therefore, in an effort to better evaluate the implementation of headgear in high school girls’ lacrosse, we compared concussion rates among high school girls’ lacrosse players in American states with a headgear mandate (HM) versus rates in states without an HM. We hypothesised that the rates of concussion among those players in states with an HM would not differ from those players in states without an HM.
Methods
Our approach used a quasi-experimental comparison that leveraged the mandatory policy of headgear use in the state of Florida (ie, headgear mandating (HM cohort)) and compared outcomes to non-headgear-mandating states (NHM cohort) across the USA. This approach used an existing national high school injury registry: the High School National Athletic Treatment, Injury and Outcomes Network (NATION). NATION is an athletic trainer (AT)-driven injury reporting registry which uses a set of common data elements. It is administered by the Datalys Center for Sports Injury Research and Prevention (Indianapolis, Indiana) and has numerous publications stemming from its use.20
Recruitment
In order to obtain a high number of player activity exposures, high school ATs were recruited to report data for high school girls’ lacrosse to NATION. ATs were incentivised with a $150 payment for each full season of reporting to NATION. ATs were recruited using publicly available contact information, outreach in collaboration with the National Athletic Trainers Association and the Athletic Training Locations and Services Project, and word of mouth. ATs were eligible to report data for the study if: (1) their high school offered a school sponsored girls’ lacrosse team, (2) the AT provided regular onsite care and athletic training services to the athletes and (3) if the AT was at a school in an NHM state where there were no school or district level HMs. ATs reported data for all high school girls’ lacrosse teams under their care (eg, varsity, junior varsity).
Data reporting
ATs who agreed to participate were referred to Datalys Center, which provided training on account management and use of the system to report AE and injury data. A detailed description of the NATION injury-surveillance methods has been published.21 In brief, ATs who participate in NATION injury-surveillance efforts collected and entered injury and exposure data into a certified electronic medical record that enabled the exporting of data to NATION.21 Deidentified exposure and injury data were then extracted from these records and checked for errors by trained, experienced NATION data quality-control staff.21
Reported concussions were operationally defined as injuries that occurred as a result of participation in a girls’ high school lacrosse game or practice and were diagnosed by an AT, physician or other healthcare professional.21 Mechanisms of concussion were categorised as player contact, surface contact, contact with equipment or other/unknown. Time loss for the concussion injuries was defined as the number of days from the injury to return to play. An AE was defined as a single athlete participating in one high school-sanctioned practice or game, regardless of duration, in which the athlete was exposed to the risk of injury.21 A game exposure required that the athlete participate in the game event to be considered exposed (ie, athletes on the sideline were not included).21 Per USA Lacrosse guidelines, individual players from the NHM cohort (ie, non-Florida states) were not restricted from the using headgear during lacrosse participation, and the de-identification process used by high school NATION precluded segregation of injuries and AEs from players using headgear in the NHM cohort.
Power analysis
A power analysis based on a normal approximation of the rate distribution was performed using publicly available data from the High School Reporting Information Online data registry.22 Using data from high school girls’ lacrosse from 2014 through 2017, an estimate of 1.4 total concussions (from games and practices) per 1000 game exposures was used to approximate a baseline non-headgear player concussion injury rate. A Poisson-distributed model with 80% power, 5% type 1 error rate and a 1:2 cohort ratio was then used to obtain an estimate of 24 509 game exposures in Florida (HM cohort) and 49 018 exposures outside of Florida (NHM cohort) in order to resolve a difference of one concussion per 1000 game exposures. Using an estimate of approximately 375 game exposures per high school (ie, 25 players over 15 games), approximately 65 HM school seasons and 130 NHM school seasons were needed to adequately power the study.
Data analysis
Concussion incidence rates (IRs) were calculated as the number (ie, frequency) of documented concussions divided by the AEs for games or practices where players had an opportunity to experience a concussion, multiplied by 1000. Concussions experienced by goalkeepers were excluded from the analyses, as players at this position use a different ‘hard-shell’ helmet standard that encompasses the entire head and face, and its use is mandatory across both cohorts. Incident rate ratios (IRRs) were calculated as the ratio of the incident rate for the NHM cohort divided by that for the HM cohort. 95% CIs were calculated for IRRs using the normal distribution for the logarithm of the rate ratio. IRRs with corresponding CIs that excluded 1.00 were deemed statistically significant. Descriptive statistics for time loss (number of days following injury until return to play) among the two cohorts include medians, SD and IQRs were also calculated.
Results
A combined 96 school seasons of data from HM high schools and 193 school seasons of data from NHM high schools were reported during the 2019 and 2021 seasons (see table 1). In total, 20 partial school seasons of data from HM high schools and 27 partial school seasons of data from NHM high schools were reported during the 2020 season prior to cancellation due to the COVID-19 pandemic. Table 1 includes the AEs reported during each of these seasons. The state-level representation of the school seasons can be found in table 2.
Athlete concussions and exposures among non-headgear mandate (NHM) and headgear mandate (HM) cohorts
High school seasons reported by state over the study period
Over the three seasons, there were a total of 141 documented concussions that occurred over 357 225 AEs, resulting in an overall rate of 0.39 concussions per 1000 AEs (95% CI: 0.33 to 0.46) (see table 3). The HM cohort experienced 25 concussions (17.7%, IR=0.27 per 1000 AEs, 95% CI: 0.17 to 0.38), while the NHM cohort had 116 concussions (82.3%, IR=0.44 per 1000 AEs, 95% CI: 0.36 to 0.52). The IRs during games were dramatically higher for both the HM (0.58, 95% CI: 0.29 to 0.88) and NHM (1.01, 95% CI: 0.78 to 1.24) cohorts than during practices. The IRRs were significantly higher for the NHM cohort during games (1.74, 95% CI: 1.00 to 3.02) and overall (1.59, 95% CI: 1.03 to 2.45), but not for practices (1.42, 95% CI: 0.71 to 2.83).
Concussion incidence among girls’ high school lacrosse players in headgear mandate (HM) states versus non-headgear mandate (NHM) states by competition type
The HM cohort included seven cases with a censored return to play date due to the end of the season or medical retirement. The remaining 18 cases had an average time loss of 17.0 (SD: 5.7 days) and a median time loss of 18.5 days (IQR: 13.25, 22.75). The NHM cohort included 33 cases with a censored return to play date due to the end of the season or medical retirement. The remaining 83 cases had an average time loss of 14.1 (SD: 14.8 days) and a median time loss of 13.0 days (IQR: 9.5, 19.5).
Discussion
Our findings provide evidence that mandated use of lacrosse headgear reduces the incidence of concussion in high school girls’ lacrosse game play. We observed that girls participating in states not mandating lacrosse headgear had a 59% greater overall incidence of concussion than those required to wear headgear. Moreover, a 74% greater incidence of concussion was observed during game play in states not mandating headgear. However, the HM was not associated with any significant differences in concussion incidence during practice. Collectively, these findings suggest that a mandate requiring the use of the ASTM F3137 standard headgear is associated with a lower incidence of concussion incidence in girls’ high school lacrosse.
Comparison to previous epidemiological investigations
Our findings are consistent with a previous smaller investigation that studied this issue on a local level.19 Baron et al followed girls’ high school lacrosse athletes from the Public Schools Athletic League of New York City, which has an HM in place. The authors compared concussion rates among their cohort from the 2017 and 2018 seasons to that of the High School RIO nationwide injury registry from 2009 to 2016. The use of the local HM was associated with a lower overall concussion rates (0.089 per 1000 AEs) compared with the nationwide cohort (0.375 per 1000 AEs).
While the concussion rates of the headgear cohort were low compared with the headgear cohort in the present investigation, the study by Baron et al was limited by the relatively small number of AEs (22 397 AEs) among the headgear cohort. In contrast, our study leveraged over four times the headgear cohort AE of this prior study. Furthermore, we used a contemporaneous cohort without headgear for comparison, as opposed to Baron et al which used historical data from a previous period with a much wider range of seasons. Additionally, game exposures in our study consisted of all participants playing with headgear or all participants playing without headgear; conversely, the game exposures in the headgear group for Baron et al consisted of games with one or both teams wearing headgear. Finally, all of the data recorded in this study were derived from the one data collection registry with one data collection technique rather than a combination of methodologies. These advantages allow for a more robust interpretation of the associations of concussion incidence with HM status in girls’ lacrosse.
Comparison to previous laboratory and biomechanical investigations
Prior research suggests the most common mechanism of concussion in girl’s lacrosse is via equipment versus player contact.5 The magnitude of impacts associated with this mechanism of injury has the potential to be particularly high, with linear and rotational acceleration magnitudes from ball and stick impacts second only to falls.23
Previous investigations support the ability of headgear meeting the ASTM F3137 standard in reducing impact magnitudes. Laboratory research using lacrosse headgear meeting the ASTM F3137 standard report a reduction in both linear and rotational accelerations.24 Similarly, a recent study investigated the effect of headgear versus no headgear conditions on peak linear accelerations and peak rotational velocities during actual game play on high school girls lacrosse players instrumented with wearable sensors.6 The headgear condition resulted in slight reductions to the mean impact magnitudes experienced by the players.6 Our findings may lend support to the notion that the headgear are effective at mitigating such impacts that may result in concussion among this cohort; however, further investigation is needed using study designs that are appropriately powered to assess concussion incidence based on mechanism of injury and impact forces.
Limitations
The primary limitation of this study is the lack of randomisation regarding the use of protective headgear. The use of players at high schools in the state of Florida for the HM cohort was necessary owing to the fact that Florida is the only state in the USA with such a mandate for girls’ lacrosse. Regardless, this design may introduce potential confounding elements that would bias the results. Possible confounders may be regional differences in game play skill and intensity and in officiating quality between the state of Florida and the remainder of the USA, although the potential role of observation clustering may be the more prominent concern. Neither is likely to have a significant effect on calculations of rates or standard errors, as any clustering would be exceedingly low and have negligible effects on SE calculations.25
The study data may also be biased by the reliance on data reported by ATs; not all high schools have athletic training services available or access to NATION surveillance, and this may limit the generalisability of the study findings to schools without such services, are more likely to be in areas with less economic resources.
Individual players in the NHM cohort were not restricted from using headgear, and the nature of the reporting system precluded segregation of data from such players in the NHM cohort. Anecdotally, the use of headgear among states outside of Florida and in areas without a local helmet mandate is exceedingly low; thus, we feel the contribution of injury and AE data from athletes using headgear in the NHM cohort to be trivial. Furthermore, given the demonstrated association of an HM with a reduced risk of concussion, any contributions from individual athletes using headgear in the NHM cohort would serve to strengthen the findings rather than diminish the relationship.
However, this assumption does pose another limitation to the current study. The comparison cohorts included games in which all players used headgear versus when all players did not use headgear; as such we are unable to make conclusions regarding games featuring players in games with mixed headgear status (eg, one team using headgear, while the other team does not). It is possible that any contribution from risk compensation may be different under such circumstances, although the prior biomechanical study by Caswell et al, which was conducted using such an environment, suggests otherwise.6
Conclusion and future directions
These findings suggest the application of a statewide mandate requiring protective headgear is associated with significantly lower risk of experiencing a concussion injury for girls’ lacrosse at the high school level of play. The results of this study are highly encouraging for athlete safety in high school girls’ lacrosse; however, a measure of caution should be employed given that this study did not employ randomisation or comparisons of injury rates pre and post mandate within the state of Florida.
It is possible that protective headgear may have similar effects in different populations of girls’ lacrosse. These may include athletes at the collegiate level or higher, athletes at the developmental or youth levels or athletes of the same age who are participating in club lacrosse. A measure of caution is necessary as significant differences in aspects such as game play, officiating performance, body control, skill development and neck strength are likely to be present at these difference levels, which may influence the association between headgear and concussion risk. In light of the current results, additional investigation is warranted for these populations.
Data availability statement
Data may be obtained from a third party (Datalys Center, Inc.; www.datalyscenter.org) and are not publicly available.
Ethics statements
Patient consent for publication
Ethics approval
The National Athletic Treatment, Injury and Outcomes Network injury-surveillance registry has been approved by the Western Institutional Review Board (Puyallup, Washington), and the current investigation was approved by the Institutional Review Board (IRB #201802880) at the University of Florida.
Acknowledgments
The authors would like to acknowledge Datalys Center, Inc., the National Athletic Trainers Association and the Athletic Training Locations and Services Project at the Korey Stringer Institute at the University of Connecticut for their assistance with this project. Furthermore, the authors would like to acknowledge the contributions of all the athletic trainers who contributed their time and effort in reporting data for this work.
References
Footnotes
Twitter @UF_SPC
Contributors DCH provided substantial contributions to the conception and design of the work, as well as the acquisition, analysis and interpretation of the data, substantial contributions to the drafting and revising of the work and final approval of the version to be published and agree to be accountable for all aspects of the work and is the guarantor for the overall content. SVC provided substantial contributions to the conception and design of the work, as well as the analysis and interpretation of the data, substantial contributions to the drafting and revising of the work and final approval of the version to be published and agree to be accountable for all aspects of the work. PMK provided substantial contributions to the design of the work, as well as the analysis and interpretation of the data, substantial contributions to the drafting and revising of the work and final approval of the version to be published and agree to be accountable for all aspects of the work. HKV provided substantial contributions to the design of the work, as well as the analysis and interpretation of the data, substantial contributions to the drafting and revising of the work and final approval of the version to be published and agree to be accountable for all aspects of the work. AEL provided substantial contributions to the design of the work, as well as the analysis and interpretation of the data, substantial contributions to the drafting and revising of the work and final approval of the version to be published and agree to be accountable for all aspects of the work.
Funding Grant support for this study was provided by USA Lacrosse and the National Operating Committee on Standards for Athletic Equipment.
Competing interests None declared.
Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.
Provenance and peer review Not commissioned; externally peer reviewed.