Concussion Incidence and Trends in 20 High School Sports Zachary Y

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Concussion Incidence and Trends in 20 High School Sports Zachary Y. Kerr, PhD, MPH,b,c Avinash Chandran, PhD, MS,b,c Aliza K. Nedimyer, MA, ATC,a,c Alan Arakkal, BS,d Lauren A. Pierpoint, PhD, MS,e Scott L. Zuckerman, MD, MPHf

BACKGROUND: Ongoing monitoring of concussion rates and distributions is important in assessing abstract temporal patterns. Examinations of high school sport-related concussions need to be updated. This study describes the epidemiology of concussions in 20 high school sports during the 2013–2014 to 2017–2018 school years. METHODS: In this descriptive epidemiology study, a convenience sample of high school athletic trainers provided injury and athlete exposure (AE) data to the National High School Sports- Related Injury Surveillance Study (High School Reporting Information Online). Concussion rates per 10 000 AEs with 95% conﬁdence intervals (CIs) and distributions were calculated. Injury rate ratios and injury proportion ratios examined sex differences in sex-comparable sports (soccer, basketball, baseball and softball, cross country, track, and swimming). We also assessed temporal trends across the study period. RESULTS: Overall, 9542 concussions were reported for an overall rate of 4.17 per 10 000 AEs (95% CI: 4.09 to 4.26). Football had the highest concussion rate (10.40 per 10 000 AEs). Across the study period, football competition-related concussion rates increased (33.19 to 39.07 per 10 000 AEs); practice-related concussion rates decreased (5.47 to 4.44 per 10 000 AEs). In all sports, recurrent concussion rates decreased (0.47 to 0.28 per 10 000 AEs). Among sex-comparable sports, concussion rates were higher in girls than in boys (3.35 vs 1.51 per 10 000 AEs; injury rate ratio = 2.22; 95% CI: 2.07 to 2.39). Also, among sex-comparable sports, girls had larger proportions of concussions that were recurrent than boys did (9.3% vs 6.4%; injury proportion ratio = 1.44; 95% CI: 1.11 to 1.88). CONCLUSIONS: Rates of football practice-related concussions and recurrent concussions across all sports decreased. Changes in concussion rates may be associated with changes in concussion incidence, diagnosis, and management. Future research should continue to monitor trends and examine the effect of prevention strategies.

’ aHuman Movement Science Curriculum, bDepartment of Exercise and Sport Science, and cMatthew Gfeller Sport- WHAT S KNOWN ON THIS SUBJECT: Previous estimates of Related Traumatic Brain Injury Research Center, University of North Carolina at Chapel Hill, Chapel Hill, North concussion incidence in high school sports are available but Carolina; dDepartment of Epidemiology, Anschutz Medical Campus, University of Colorado Denver, Aurora, dated. Ongoing monitoring of injury incidence provides the Colorado; eSteadman Philippon Research Institute, Vail, Colorado; and fDepartment of Neurological Surgery, and opportunity for clinicians and researchers to understand how Sports Concussion Center, School of Medicine, Vanderbilt University, Nashville, Tennessee concussion rates and distributions may have changed over time.

Dr Kerr co-led the conceptualization and design of the study, led analyses and data interpretation, WHAT THIS STUDY ADDS: During the 2013–2014 to 2017–2018 and drafted the initial manuscript; Dr Chandran co-led the conceptualization and design of the academic years, the rates of football practice concussions and study, led analyses and data interpretation, and assisted with the drafting of the manuscript; Ms recurrent concussions across all sports decreased. Competition Nedimyer assisted with the conceptualization and design of the study, assisted with analyses and concussion rates increased in football. Concussion incidence was also higher in the latter halves of competitions and practices data interpretation, and assisted with the drafting of the manuscript; Mr Arakkal and Dr Pierpoint across numerous sports. assisted in the coordination of data collection, management, analyses, and interpretation and reviewed and revised the manuscript; Dr Zuckerman assisted with the conceptualization and design of the study, assisted with analyses and data interpretation, and reviewed and revised the To cite: Kerr ZY, Chandran A, Nedimyer AK, et al. manuscript; and all authors approved the ﬁnal manuscript as submitted and agree to be Concussion Incidence and Trends in 20 High School accountable for all aspects of the work. Sports. Pediatrics. 2019;144(5):e20192180

Downloaded from www.aappublications.org/news by guest on September 25, 2021 PEDIATRICS Volume 144, number 5, November 2019:e20192180 ARTICLE Concussions in high school sports during the 2013–2014 to 2017–2018 and featured 20 sports with have resonated as a major public academic years. participation varying by sport and health problem. Such concern year. The 20 sports included in this originates from previous research study were as follows: boys’ football, that has found concussion to be METHODS wrestling, soccer, basketball, baseball, 1–4 a common sport-related injury and Data originated from the National cross country, ice hockey, lacrosse, associated with adverse short- and High School Sports-Related Injury swimming and diving, and track and fi ’ long-term health-related Surveillance Study (High School eld; girls volleyball, soccer, 5–9 outcomes. It has been speculated Reporting Information Online [HS basketball, softball, cross country, fi that such concerns about concussion RIO]) during 5 academic years eld hockey, lacrosse, swimming and fi may have contributed to the decline (2013–2014 to 2017–2018). This diving, and track and eld; and coed in participation in football (a 4.6% study was deemed exempt by the cheerleading. decrease in high school 11-player Colorado Multiple Institutional ATs from participating high schools football from 2012–2013 to Review Board, Aurora, Colorado. The reported injury incidence and athlete 2017–2018).10,11 Despite this, data methodology of HS RIO has been exposure (AE) information weekly from the National Federation of State 17,18 previously described but is throughout the academic year using High School Associations has summarized below. a secure Web site. For each injury, the indicated a steady rise in high school AT completed a detailed injury report sports participation overall (a 3.5% HS RIO data originated from a sample (body part, diagnosis, mechanism, increase from 2012–2013 to of high schools with 1 or more activity, position, recurrence, etc). A 2017–2018).10 athletic trainers (ATs) that had valid reportable AE was defined as 1 e-mail addresses. Two data collection 12 athlete participating in 1 school- The van Mechelen et al sequence of panels during the study period were sanctioned practice or competition. prevention framework emphasizes available. The first panel collected Our injury of focus, concussion, was that injury prevention is a cyclical data from a random sample of ∼100 defined as (1) occurring as a result of process that includes examining high schools that were recruited participation in an organized practice incidence, etiology, and preventive annually to report data for 9 original or competition, (2) requiring medical measures associated with injury; sports of interest (boys’ football, attention by an AT or physician, and most importantly, it encourages the wrestling, soccer, basketball, and (3) being diagnosed as a concussion. ongoing monitoring of injury baseball and girls’ volleyball, soccer, Although other injuries collected via incidence for longitudinal basketball, and softball). These high HS RIO were only included if they assessments. Although previous schools were categorized into 8 strata resulted in participation restriction estimates of concussion incidence in based on cross-sections of school time $24 hours, all concussions high school sports are available,2,13,14 population (enrollment #1000 or regardless of participation restriction most recently from the 2011–2012 to .1000) and US Census geographic time were included. We did not 2013–2014 academic years,13 the region (Midwest, Northeast, South, provide a definition for concussion identification, diagnosis, and and West).19 If a school dropped out because we relied on the expertise of management of concussion is of the system, a replacement from the the ATs and any additional team a rapidly evolving area of medicine, same stratum was selected. The medical staff. Nonetheless, with new scientific findings and second panel consisted of an concussion consensus statements policy changes regularly being additional convenience sample of were available to medical staff.15,20 implemented.15 Ongoing monitoring high schools recruited annually that Internal validity checks conducted by of injury incidence provides the reported data for additional sports of HS RIO staff have consistently found opportunity for clinicians and interest (eg, boys’ cross country, ice sensitivity, specificity, positive researchers to understand how hockey, lacrosse, swimming, and predictive value, and negative concussion rates and distributions track; girls’ cross country, field predictive value .90%.21 may have changed over time,12 hockey, lacrosse, swimming, and especially in relation to policy, track; and cheerleading) and any of Data were analyzed by using SAS considering that all 50 states in the the original 9 sports of interest. ATs (version 9.4; SAS Institute, Inc, Cary, United States and the District of at schools from the first panel could NC). Concussion frequencies, Columbia have legislation related to also contribute data to the second distributions, and rates per 10 000 concussion management.16 In this panel by reporting data for sports AEs with 95% confidence intervals study, we aimed to describe the outside of the original 9 sports of (CIs) were calculated. Injury rate epidemiology of concussions interest. Data considered for this ratios (IRRs)22 compared concussion sustained in high school sports study originated from both panels rates by event type (ie, competition or

Downloaded from www.aappublications.org/news by guest on September 25, 2021 2 KERR et al EITISVlm 4,nme ,Nvme 2019 November 5, number 144, Volume PEDIATRICS TABLE 1 Concussion Counts and Rates Among High School Athletes in 20 Sports During the 2013–2014 to 2017–2018 Academic Years Sport No. Concussions No. AEs Rates per 10 000 AEsa Competition Versus Practice Rate Ratio (95% CI) Competition Practice Overall Competition Practice Overall Competition Practice Overall Boys-only sports Football 2521 1662 4183 703 784 3 319 623 4 023 407 35.82 5.01 10.40 7.15 (6.73 to 7.61)b Ice hockey 187 21 208 95 854 174 769 270 623 19.51 1.20 7.69 16.24 (10.34 to 25.49)b Lacrosse 256 67 323 196 296 460 069 656 365 13.04 1.46 4.92 8.96 (6.84 to 11.72)b Wrestling 292 273 565 294 452 874 227 1 168 679 9.92 3.12 4.83 3.18 (2.69 to 3.75)b Soccer 421 107 528 450 768 1 029 898 1 480 666 9.34 1.04 3.57 8.99 (7.27 to 11.11)b Basketball 224 152 376 544 463 1 225 492 1 769 955 4.11 1.24 2.12 3.32 (2.70 to 4.08)b Downloaded from Baseball 96 40 136 461 197 851 518 1 312 715 2.08 0.47 1.04 4.43 (3.06 to 6.41)b Swimming 4 14 18 88 029 396 751 484 780 0.45 0.35 0.37 1.29 (0.42 to 3.91) Track and ﬁeld 11 14 25 273 956 1 173 477 1 447 433 0.40 0.12 0.17 3.37 (1.53 to 7.41)b Cross country 0 4 4 119 026 595 291 714 317 0.00 0.07 0.06 N/A Girls-only sports Soccer 864 191 1055 396 309 891 423 1 287 732 21.80 2.14 8.19 10.17 (8.70 to 11.90)b www.aappublications.org/news Basketball 504 142 646 416 477 916 289 1 332 766 12.10 1.55 4.85 7.81 (6.48 to 9.41)b Lacrosse 152 57 209 151 826 343 593 495 419 10.01 1.66 4.22 6.03 (4.45 to 8.18)b Volleyball 236 187 423 445 344 899 742 1 345 086 5.30 2.08 3.14 2.55 (2.10 to 3.09)b Field hockey 77 22 99 118 323 253 266 371 589 6.51 0.87 2.66 7.49 (4.66 to 12.03)b Softball 133 92 225 338 722 642 798 981 520 3.93 1.43 2.29 2.74 (2.10 to 3.58)b Swimming 8 28 36 101 238 445 615 546 853 0.79 0.63 0.66 1.26 (0.57 to 2.76) Track and ﬁeld 16 19 35 231 208 987 341 1 218 549 0.69 0.19 0.29 3.60 (1.85 to 6.99)b Cross country 3 5 8 101 000 511 038 612 038 0.30 0.10 0.13 3.04 (0.73 to 12.70) Coed sports: cheerleadingc 74 366 440 333 758 1 016 114 1 349 872 2.22 3.60 3.26 0.62 (0.48 to 0.79)b Boys’ sex-comparable sports totald 756 331 1087 1 937 439 5 272 427 7 209 866 3.90 0.63 1.51 6.22 (5.46 to 7.07)b

byguest on September25, 2021 Girls’ sex-comparable sports totald 1528 477 2005 1 584 954 4 394 504 5 979 458 9.64 1.09 3.35 8.88 (8.01 to 9.84)b Overall total 6079 3463 9542 5 862 030 17 008 334 22 870 364 10.37 2.04 4.17 5.09 (4.89 to 5.31)b N/A, not applicable. a One athlete participating in 1 practice or 1 competition. b Denotes statistical significance (IRR, 95% CI does not include 1.00). c Competition category also includes performance events for cheerleading. d Only includes sports in which both sexes participated (ie, soccer, basketball, baseball or softball, cross country, swimming, and track and field). 3 practice) and by sex in sex- 0.0 were considered statistically (10.37 vs 2.04 per 10 000 AEs; IRR = comparable sports (ie, soccer, significant. 5.09; 95% CI: 4.89 to 5.31; Table 1). basketball, baseball or softball, cross Sport-specific findings were generally country, track, and swimming). consistent with overall findings in RESULTS Lacrosse was not considered a sex- this regard. However, in cheerleading, comparable sport because rules Concussion Frequencies the concussion rate in competition regarding contact vary between the was lower than that in practice (2.22 During the 2013–2014 to 2017–2018 boys’ and girls’ sports. An example of vs 3.60 per 10 000 AEs; IRR = 0.62; academic years, 9542 concussions an IRR comparing competition and 95% CI: 0.48 to 0.79). were reported from the study sample practice rates is as follows: (Table 1). Of these, 63.7% occurred When examining sex-comparable + competition concussions during competitions, and 36.3% sports (ie, soccer, basketball, baseball + competition AEs occurred during practices. Most or softball, cross country, swimming, IRR 5 : fi + practice concussions concussions were reported in the and track and eld), the overall + practice AEs regular season (81.6%), followed by concussion rate was higher in girls the preseason (14.2%) and the than in boys (3.35 vs 1.51 per 10 000 Injury proportion ratios (IPRs)22 postseason (3.3%); 0.9% of AEs; IRR = 2.22; 95% CI: 2.07 to 2.39; fi compared distributions by injury concussions did not have time-in- Table 2). This nding was retained fi mechanism and recurrence. An season data. when examining speci csex- example of an IPR comparing the comparable sport pairs and when Concussion Rates proportion of concussions that were restricted to competitions or due to contact with another person The 9542 reported concussions practices only; however, some IRRs between boys and girls is as follows: occurred during 22 870 364 AEs for were no longer statistically 0 1 significant. + an overall rate of 4.17 per 10 000 AEs concussions due ’ Bto contact with another C (95% CI: 4.09 to 4.26; Table 1). Boys Sufficient evidence of temporal trends B person among boys C football had the highest overall @ + total concussions A across the study period was found among boys concussion rate (10.40 per 10 000 only in boys’ football (Fig 1). Whereas IPR 5 0 1: AEs), followed by girls’ soccer (8.19 + concussions due the competition rate had increased B to contact with C per 10 000 AEs) and boys’ ice hockey ’ Banother person among girlsC over time in boys football (annual (7.69 per 10 000 AEs). Findings were @ + total concussions A average change of 1.56 per 10 000 among girls similar when examining concussion AEs; 95% CI: 1.13 to 2.00), the rates in competition. When examining practice rate had decreased (annual IRRs and IPRs with 95% CIs concussion incidence in practice, the average change of 20.28 per 10 000 ’ excluding 1.00 were considered highest rates were observed in boys AEs; 95% CI: 20.37 to 20.18). statistically significant. Linear football (5.01 per 10 000 AEs), regression was used to analyze trends followed by cheerleading (3.60 per Timing of Concussion Within Event 10 000 AEs) and boys’ wrestling (3.12 in concussion rates across the study Of the 3463 practice-related per 10 000 AEs). period and estimate average annual concussions reported, most occurred changes (ie, mean differences). Mean Overall, the concussion rate was after the first hour of practice (66.9%; differences with 95% CIs excluding higher in competition than practice Table 3). Although competition- related concussion data were TABLE 2 Comparison of Sport-Related Concussion Rates Among High School Athletes During the stratified by sport, larger proportions 2013–2014 to 2017–2018 Academic Years of concussions were typically Sport Girls Versus Boys, IRR (95% CI) reported in the latter half of competitions. Among concussions Competition Practice Overall reported in sports with quarters or a a Basketball 2.94 (2.51 to 3.44) 1.25 (0.99 to 1.57) 2.28 (2.01 to 2.59) halves (ie, boys’ football, lacrosse, Cross country N/A 1.46 (0.39 to 5.42) 2.33 (0.70 to 7.75) ’ Soccer 2.33 (2.08 to 2.62)a 2.06 (1.63 to 2.61)a 2.30 (2.07 to 2.55)a soccer, and basketball and girls Softball or baseball 1.89 (1.45 to 2.45)a 3.05 (2.10 to 4.42)a 2.21 (1.79 to 2.74)a lacrosse, field hockey, soccer, and Swimming 1.74 (0.52 to 5.78) 1.78 (0.94 to 3.38) 1.77 (1.01 to 3.12)a basketball), 54.5% were reported to Track and field 1.72 (0.80 to 3.71) 1.61 (0.81 to 3.22) 1.66 (0.995 to 2.78) have occurred in the second half, or b a a a Sex-comparable sports overall 2.47 (2.26 to 2.70) 1.73 (1.50 to 1.99) 2.22 (2.07 to 2.39) third or fourth quarters compared N/A, not applicable. with 29.4% in the first half, or first or a Denotes statistical significance (IRR, 95% CI does not include 1.00). b Only includes sports in which both sexes participated (ie, soccer, basketball, baseball or softball, cross country, second quarters. Precompetition- swimming, and track and field). and/or warm-up–related concussions

Downloaded from www.aappublications.org/news by guest on September 25, 2021 4 KERR et al accounted for relatively small proportions of all reported concussions in most sports; the 2 exceptions were girls’ volleyball (27.5%) and girls’ softball (26.3%).

Injury Mechanism Distributions Most concussions were due to contact with another person (62.3%), followed by contact with the surface (17.5%) and contact with equipment or an apparatus (15.8%; Table 4). In sex-comparable sports, the proportion of concussions due to contact with another person was higher in boys than in girls (54.5% vs 42.1%; IPR = 1.29; 95% CI: 1.20 to 1.39). In contrast, the proportion of concussions due to contact with equipment or an apparatus was higher in girls than in boys (33.6% vs 23.5%; IPR = 1.43; 95% CI: 1.27 to 1.62). Table 5 summarizes the most sport-speciﬁc common injury mechanism, injury activity clusters, and positions with concussions.

Recurrent Sport-Related Concussions Overall, 8.3% of reported concussions were recurrent (Fig 2). The sports with the largest proportions of concussions that were recurrent were boys’ ice hockey (14.4%), boys’ lacrosse (12.1%), and girls’ ﬁeld hockey (12.1%). Among sex- comparable sports, the proportion of concussions that were recurrent was higher in girls than in boys (9.3% vs 6.4%; IPR = 1.44; 95% CI: 1.11 to 1.88). However, the proportion of concussions that were recurrent was higher in baseball than in softball (11.0% vs 4.4%; IPR = 2.48; 95% CI: 1.15 to 5.37). Linear trend tests found evidence of decreases in the recurrent concussion rate across the study period (Fig 1). This annual average change was the greatest in boys’ football (annual FIGURE 1 average change of 20.13 per 10 000 Annual sport-related concussion rates among high school athletes in 20 sports during the 2 2 2013–2014 to 2017–2018 academic years. A reportable AE was deﬁned as 1 athlete participating in AEs; 95% CI: 0.19 to 0.07). 1 school-sanctioned practice or competition. A, Overall. B, In competitions. C, In practices. D, Among Decreases were also observed in all recurrent sport-related concussions. other sports (annual average change

Downloaded from www.aappublications.org/news by guest on September 25, 2021 PEDIATRICS Volume 144, number 5, November 2019 5 TABLE 3 Distributions of Timing of Concussions Within Events Among High School Athletes in 20 of 20.03 per 10 000 AEs; 95% CI: Sports During the 2013–2014 to 2017–2018 Academic Years 20.05 to 20.02). Sport Time in Event n (%) Boys’ football DISCUSSION Precompetition or warm-ups 10 (0.4) First quarter 169 (6.7) Understanding concussion incidence Second quarter 628 (24.9) and prevention is important given the Third quarter 694 (27.5) growing population of high school Fourth quarter 672 (26.7) athletes and rapidly changing field of Overtime 10 (0.4) 10 Missing 338 (13.4) concussion management. Our study Boys’ ice hockey updates previous literature on high Precompetition or warm-ups 0 school sports concussion First period 21 (11.2) incidence2,13,14 and provides Second period 70 (37.4) additional information about Third period 60 (32.1) Overtime 1 (0.5) emerging trends in incidence. Our Missing 35 (18.7) study is unable to directly examine Boys’ lacrosse the causes of increased concussion Precompetition or warm-ups 2 (0.8) risk or the effects of past prevention First quarter 19 (7.4) efforts. Still, because the van Second quarter 58 (22.7) 12 Third quarter 68 (26.6) Mechelen et al sequence of Fourth quarter 68 (26.6) prevention framework emphasizes Missing 41 (16.0) ongoing monitoring of injury Boys’ wrestling incidence, we believe our findings Precompetition or warm-ups 4 (1.4) will benefit clinicians by helping First period 39 (13.4) Second period 96 (32.9) guide future prevention and research Third period 71 (24.3) directions. Missing 82 (28.1) Boys’ soccer Trends in Concussion Rates Precompetition or warm-ups 9 (2.1) First half 107 (25.4) Concussion rates in the current study Second half 242 (57.5) were generally higher than previous Overtime 3 (0.7) estimates from similar surveillance- Missing 60 (14.3) based studies using data from other Boys’ basketball time periods.2,13,14 Likewise, we Precompetition or warm-ups 3 (1.3) First quarter 20 (8.9) observed decreasing rates of Second quarter 63 (28.1) recurrent concussions. Data from Third quarter 56 (25.0) previous studies were generally Fourth quarter 47 (21.0) collected during a period in which Overtime 0 mandatory concussion legislation Missing 35 (15.6) Boys’ baseball governing high school sports did not Pre-competition/warm-ups 2 (2.1) exist (such legislation currently exists Innings 1–4 43 (44.8) in all 50 states and the District of Innings 5–7 24 (25.0) Columbia).16 Such legislation has Extra innings 3 (3.1) been found to be associated with Missing 24 (25.0) Girls’ soccer increased concussion rates (likely due Precompetition or warm-ups 17 (2.0) to increased reporting) and decreased First half 228 (26.4) recurrent concussion rates Second half 494 (57.2) (hypothesized to be due to better Overtime 3 (0.4) concussion management that Missing 122 (14.1) Girls’ basketball legislation advocated, including Precompetition or warm-ups 15 (3.0) mandatory removal from play and First quarter 27 (5.4) requirements associated with return Second quarter 109 (21.6) to play).23–25 Future research may Third quarter 139 (27.6) inform concussion prevention in 2 Fourth quarter 128 (25.4) Overtime 1 (0.2) manners. First, concussion legislation 16 Missing 85 (16.9) varies by state ; future research

Downloaded from www.aappublications.org/news by guest on September 25, 2021 6 KERR et al TABLE 3 Continued examinations for such changes in Sport Time in Event n (%) concussion rates are warranted. Girls’ lacrosse Furthermore, policy and rule changes Precompetition or warm-ups 11 (7.2) must be evaluated to ensure that they First half 25 (16.5) provide their intended outcomes, Second half 85 (55.9) particularly when introduced from Missing 31 (20.4) higher levels of play (eg, professional Girls’ volleyball Precompetition or warm-ups 65 (27.5) and collegiate) to lower levels. First set 5 (2.1) Finally, it is important to consider Second set 68 (28.8) Third set 38 (16.1) that cheerleading was the only sport Fourth set 8 (3.4) in which the concussion rate was Fifth set 3 (1.3) higher in practice than in Missing 49 (20.8) competition. Not all states recognize Girls’ field hockey cheerleading as a sport, and cheer Precompetition or warm-ups 4 (5.2) First half 22 (28.6) squads may practice in less-than- Second half 43 (55.8) ideal places (eg, hallways and on Missing 8 (10.4) asphalt)34 and may have less access to medical oversight and coaching Girls’ softball support compared with other Precompetition or warm-ups 35 (26.3) Innings 1–4 40 (30.1) high school sports. Pediatricians Innings 5–7 30 (22.6) should ensure that youth athletes Extra innings 1 (0.8) and their families are aware of Missing 27 (20.3) the concussion risk associated All sports practices with their sports of interest. Within first hour 799 (23.1) 1–2 h 2015 (58.2) Furthermore, pediatricians working .2 h 300 (8.7) with youth sports organizations Missing 349 (10.1) should advocate the use of safety Time-in-competition data were not available for boys’ and girls’ cross country, swimming, and track and field and measures to help prevent cheerleading. Whereas time-in-practice data could be pooled, time-in-competition data were provided by sport to account concussions. for variations in coding. Sex Differences in Concussion Incidence should identify specific legislative lacrosse. Although we found evidence Concussion rates were higher among components most strongly associated of decreasing practice-related girls than boys in sex-comparable with changes in concussion concussion rates in football (possibly sports. This result was found within incidence to help improve and clarify due to efforts to limit contact multiple sports, although statistical existing requirements.26 Second, exposure in practices),30,31 there was significance was likely not achieved in because the reported concussion also evidence of increasing rates in sports such as cross country and incidence may be affected by the competitions. Thus, concussion track because of low counts of potential increase in reporting,14,27 prevention efforts in football should concussions during the 5-year study continued longitudinal research is target competitions alongside period. Findings related to sex needed. practices. The American Academy of differences are prevalent throughout Pediatrics advocates teaching proper concussion literature,2,13,28,29 and As previously seen in high school tackling and enforcing rules that potential associated factors have 2,12,13 28,29 sports and other settings, discourage improper technique.32 included differences in disclosure, football maintained the highest Simultaneously, kickoff rule changes neck musculature, cerebral blood observed concussion rate. Although at the collegiate level have been flow and/or cerebrovascular this was likely due to the inherent found to be associated with reduced organization, hormonal regulation, element of collision in the sport, it is concussion rates.33 It is also, etc.35–40 However, few studies have important to consider why football unfortunately, possible that attempted to directly assess these consistently has a concussion rate decreasing contact exposure may factors in relation to incidence. Also, higher than other sports in which impact skill development and place our study found that the proportions intentional contact is allowed, such as players at increased injury risk of concussions among sex- wrestling, boys’ ice hockey, and boys’ during games. More in-depth comparable sports that were

Downloaded from www.aappublications.org/news by guest on September 25, 2021 PEDIATRICS Volume 144, number 5, November 2019 7 TABLE 4 Sport-Related Concussion Counts Among High School Athletes in 20 Sports by Injury Mechanism During the 2013–2014 to 2017–2018 Academic Years Sports Injury Mechanism, n (%) Total, n (%) Contact With Another Person Contact With Surface Contact With Equipment Other Boys-only sports Football 3497 (83.6) 425 (10.2) 32 (0.8) 229 (5.5) 4183 (100.0) Ice hockey 125 (60.1) 51 (24.5) 24 (11.5) 8 (3.8) 208 (100.0) Lacrosse 206 (63.8) 28 (8.7) 78 (24.1) 11 (3.4) 323 (100.0) Wrestling 226 (40.0) 301 (53.3) 9 (1.6) 29 (5.1) 565 (100.0) Soccer 285 (54.0) 69 (13.1) 155 (29.4) 19 (3.6) 528 (100.0) Basketball 247 (65.7) 107 (28.5) 14 (3.7) 8 (2.1) 376 (100.0) Baseball 51 (37.5) 8 (5.9) 74 (54.4) 3 (2.2) 136 (100.0) Swimming 8 (44.4) 7 (38.9) 1 (5.6) 2 (11.1) 18 (100.0) Track and field 0 12 (48.0) 11 (44.0) 2 (8.0) 25 (100.0) Cross country 1 (25.0) 2 (50.0) 0 1 (25.0) 4 (100.0) Girls-only sports Soccer 417 (39.5) 156 (14.8) 431 (40.9) 51 (4.8) 1055 (100.0) Basketball 358 (55.4) 203 (31.4) 69 (10.7) 16 (2.5) 646 (100.0) Lacrosse 35 (16.7) 18 (8.6) 151 (72.2) 5 (2.4) 209 (100.0) Volleyball 79 (18.7) 105 (24.8) 228 (53.9) 11 (2.6) 423 (100.0) Field hockey 41 (41.4) 11 (11.1) 46 (46.5) 1 (1.0) 99 (100.0) Softball 58 (25.8) 12 (5.3) 150 (66.7) 5 (2.2) 225 (100.0) Swimming 9 (25.0) 16 (44.4) 6 (16.7) 5 (13.9) 36 (100.0) Track and field 2 (5.7) 11 (31.4) 18 (51.4) 4 (11.4) 35 (100.0) Cross country 1 (12.5) 5 (62.5) 0 2 (25.0) 8 (100.0) Coed sports: cheerleadinga 295 (67.0) 127 (28.9) 6 (1.4) 12 (2.7) 440 (100.0) Boys’ sex-comparable sports totalb 592 (54.5) 205 (18.9) 255 (23.5) 35 (3.2) 1087 (100.0) Girls’ sex-comparable sports totalb 845 (42.1) 403 (20.1) 674 (33.6) 83 (4.1) 2005 (100.0) Overall total 5941 (62.3) 1674 (17.5) 1503 (15.8) 424 (4.4) 9542 (100.0) a Competition category also includes performance events for cheerleading. b Only includes sports in which both sexes participated (ie, soccer, basketball, baseball or softball, cross country, swimming, and track and field). recurrent and due to equipment levels of play, they may still lack instances in which fatigue is resulting contact were higher in girls than in aspects of skill development and in reckless play. Primary prevention boys, which may also contribute to physical literacy. All high school strategies including monitoring and the differences in concussion coaches need to be properly educated removing fatigued athletes from play incidence between the sexes. in their roles to ensure age- when feasible are recommended. Research that isolates the specific appropriate training and gameplay. fi etiological factors associated with sex Despite this nding, we also found that more than one-quarter of differences is needed to assist Concussions in Latter Segments of clinicians in properly highlighting competition-related concussions in Competitions and Practices ’ ’ potential preventive factors to reduce girls volleyball and girls softball concussion incidence. In both competition and practice, occurred in precompetition or warm- more concussions were generally ups. We were unable to pinpoint the reported in the latter segments of factors associated with these findings. Equipment-Related Contact each event type, which concurs with In girls’ volleyball, both teams may Mechanisms previous research.41–43 In sports in warm up on their respective court Approximately 1 in 6 concussions which contact occurs intentionally or sides at the same time; thus, players overall were due to contact with unintentionally, athletes who are may not pay attention to the actions equipment or an apparatus. In more fatigued may be less able to of the opposing team, which could a recent report from The Aspen defend themselves and/or be less lead to unintended ball contact when Institute,11 large proportions of youth aware of oncoming collisions. Also, balls were spiked over the net by the sport coaches were found to not be athletes on the opposing team who opposing team. In response, the trained in 6 core competencies, are fatigued may put other players at National Federation of High School including sport-specific skills and risk due to playing with less technical Associations released a rule change in tactics. Although high school athletes craft.44 Game-officiating and referee- 2018–2019 not allowing balls to be may have had experience playing education programs should be hit over the net during warm-ups.45 their sports at earlier ages and lower adapted to be more sensitive to In girls’ softball, warm-ups may

Downloaded from www.aappublications.org/news by guest on September 25, 2021 8 KERR et al TABLE 5 Concussion Injury Mechanism, Activity Combinations, and Positions Among High School Athletes in 20 Sports During the 2013–2014 to 2017–2018 Academic Years Sport Most Common Injury Mechanism and Activity Combinations n (%) Most Common Positions n (%) Boys’ football Contact with another person while tackling on a defensive running play 470 (11.2) Linebacker 531 (12.7) Contact with another person while being tackled on an offensive running play 458 (11.0) Running back 489 (11.7) Boys’ ice hockey Contact with another person while skating 44 (21.2) Wing 97 (46.6) Contact with another person while being checked 35 (16.8) Defense 51 (24.5) Center 26 (12.5) Boys’ lacrosse Contact with another person while being body checked 35 (10.8) Midfielder 111 (34.4) Contact with another person while chasing a loose ball 26 (8.1) Attack 93 (28.8) Defense 73 (22.6) Boys’ wrestling Contact with surface during takedown 184 (32.6) —— Contact with another person while sparring 80 (14.2) —— Contact with another person during takedown 77 (13.6) —— Boys’ soccer Contact with another person while heading the ball 90 (17.1) Midfield 177 (33.5) Contact with another person during general play 46 (8.7) Defense 103 (19.5) Forward 98 (18.6) Goalkeeper 71 (13.5) Boys’ basketball Contact with another person while rebounding 51 (13.6) Guard 167 (44.4) Contact with another person while chasing a loose ball 40 (10.6) Forward 110 (29.3) Contact with another person while defending 39 (10.4) Center 43 (11.4) Contact with another person during general play 38 (10.1) Boys’ baseball Contact with another person while fielding a batted ball 17 (12.5) Outfielder 28 (20.6) Hit by pitch while batting 13 (9.6) Baseman 26 (19.1) Catcher 20 (14.7) Boys’ swimming Wall contact while turning off the wall 4 (22.2) —— Contact with another person while swimming 3 (16.7) —— Boys’ track and field Contact with field equipment while jumping or landing 4 (16.0) Pole vaulter 8 (32.0) Contact with a surface while jumping or landing 4 (16.0) Girls’ soccer Ball contact while heading the ball 141 (13.4) Midfield 349 (33.1) Contact with another person while heading the ball 115 (10.9) Defense 231 (21.9) Forward 222 (21.0) Goalkeeper 106 (10.1) Girls’ basketball Contact with another person while rebounding 70 (10.8) Guard 314 (48.6) Contact with another person while defending 69 (10.7) Forward 176 (27.2) Contact with another person during general play 67 (10.4) Contact with another person while chasing a loose ball 65 (10.1) Girls’ lacrosse Ball contact while defending 21 (10.0) Midfielder 56 (26.8) Ball contact while receiving a pass 16 (7.7) Attack 54 (25.8) Ball contact while goaltending 16 (7.7) Defense 43 (20.6) Ball contact while being stick checked 16 (7.7) Goalkeeper 21 (10.1) Girls’ volleyball Contact with a surface while digging 63 (14.9) Outside hitter 98 (23.2) Contact with the ball during general play 59 (13.9) Setter 58 (13.7) Middle blocker 56 (13.2) Libero 55 (13.0) Girls’ field hockey Ball contact while defending 18 (18.2) Midfielder 35 (35.4) Contact with another person while handling the ball 13 (13.1) Forward 24 (24.2) Defender 20 (20.2) Girls’ softball

Downloaded from www.aappublications.org/news by guest on September 25, 2021 PEDIATRICS Volume 144, number 5, November 2019 9 TABLE 5 Continued Sport Most Common Injury Mechanism and Activity Combinations n (%) Most Common Positions n (%) Hit by a ball while fielding a batted ball 23 (10.2) Outfielder 52 (23.1) Contact with another person while fielding a batted ball 21 (9.3) Baseman 45 (20.0) Catcher 23 (10.2) Girls’ swimming Contact with another person while swimming 5 (13.9) —— Wall contact while turning off the wall 5 (13.9) —— Girls’ track and field Contact with a surface while running 5 (14.3) Pole vaulter 7 (20.0) Cheerleading Contact with another person during a partner stunt 116 (26.4) Base 223 (50.7) Contact with another person during a toss 84 (19.1) Flyer 122 (27.7) Contact with another person during a pyramid 55 (12.5) Boys’ and girls’ cross country were excluded from because of concussion counts ,10. —, not applicable. include numerous balls in motion in schools, particularly those without accurately detect and diagnose various areas of the field at once, ATs.46 Underreporting may have injuries. Furthermore, previous which may place athletes at risk for occurred if players chose not to research has found ATs to have high being hit by a ball. Additional disclose concussion symptoms, thus agreement with physicians in 47 exploration of such potential causes compromising our ability to fully diagnosing injuries and to provide and appropriate prevention strategies understand athlete injury histories. higher-quality data collection to reduce risk are needed. Our study also did not provide compared with nonmedically trained a working definition of concussion, individuals, such as coaches or other players.48 This study was unable to Limitations nor could it account for account for factors potentially underreporting and/or misdiagnosis. Only data from high schools with ATs associated with concussion incidence, fi However, all injuries were assessed were included. Therefore, the ndings such as implemented injury of this study may not be generalizable and documented by medical prevention programs and athlete- to the overall population of high professionals who were trained to specific characteristics (eg, maturation status, previous injury history, functional capabilities, etc). Lastly, our study calculated injury rates using AE, which may not be as precise an at-risk exposure measure as minutes or hours, or the total number of game plays across a season.27 HS RIO also does not acquire AE by position or starter status, thereby precluding our ability to calculate more specific injury rates. However, collection of such exposure data is more laborious and may be too burdensome for ATs contributing to HS RIO.

CONCLUSIONS Using surveillance data from the 2013–2014 to 2017–2018 academic years, we found that football remained the high school sport with the highest concussion rate, with FIGURE 2 decreasing practice concussion rates Proportions of sport-related recurrent concussions by sport during the 2013–2014 to 2017–2018 academic years. a Only includes sports in which both sexes participated (ie, soccer, basketball, observed; however, increasing baseball or softball, cross country, swimming, and track and ﬁeld). competitions rates highlight the

Downloaded from www.aappublications.org/news by guest on September 25, 2021 10 KERR et al continued need for prevention the latter halves of events. a tremendously positive effect on the strategies. Decreasing recurrent Pediatricians should provide such safety of high school student athletes. concussion rates may be associated updated information to youth athletes with changes in concussion diagnosis to help them and their families and management in high school sport understand the risk of concussion in ABBREVIATIONS their sports of interest. settings, such as those elicited by AE: athlete exposure concussion-based legislation. Future AT: athletic trainer research should also target risk and CI: conﬁdence interval ACKNOWLEDGMENTS preventive factors in other sports that HS RIO: High School Reporting allow contact, the role of skill We thank the many ATs who have Information Online development to reduce equipment- volunteered their time and efforts to IPR: injury proportion ratio related contact, and strategies to submit data to HS RIO. Their efforts IRR: injury rate ratio mitigate increased concussion risk in are greatly appreciated and have had

DOI: https://doi.org/10.1542/peds.2019-2180 Accepted for publication Aug 7, 2019 Address correspondence to Zachary Y. Kerr, PhD, MPH, Department of Exercise and Sport Science, University of North Carolina at Chapel Hill, 313 Woollen Gym, CB#8700, Chapel Hill, NC 27599-8700. E-mail: [email protected] PEDIATRICS (ISSN Numbers: Print, 0031-4005; Online, 1098-4275). Copyright © 2019 by the American Academy of Pediatrics FINANCIAL DISCLOSURE: The authors have indicated they have no financial relationships relevant to this article to disclose. FUNDING: This report represents data collection from High School Reporting Information Online. These data were provided by Dr R. Dawn Comstock of the Colorado School of Public Health and the University of Colorado School of Medicine. High School Reporting Information Online was funded in part by the Centers for Disease Control and Prevention (grants R49/CE000674-01 and R49/CE001172-01) and the National Center for Research Resources (award KL2 RR025754). The authors also acknowledge the research funding contributions of the National Federation of High School Associations, National Operating Committee on Standards for Athletic Equipment, DonJoy Orthotics, and EyeBlack. The content of this report is solely the responsibility of the authors and does not necessarily represent the official views of the funding organizations. POTENTIAL CONFLICT OF INTEREST: The authors have indicated they have no potential conflicts of interest to disclose.

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Downloaded from www.aappublications.org/news by guest on September 25, 2021 PEDIATRICS Volume 144, number 5, November 2019 13 Concussion Incidence and Trends in 20 High School Sports Zachary Y. Kerr, Avinash Chandran, Aliza K. Nedimyer, Alan Arakkal, Lauren A. Pierpoint and Scott L. Zuckerman Pediatrics originally published online October 15, 2019;

Updated Information & including high resolution figures, can be found at: Services http://pediatrics.aappublications.org/content/early/2019/10/11/peds.2 019-2180 References This article cites 39 articles, 3 of which you can access for free at: http://pediatrics.aappublications.org/content/early/2019/10/11/peds.2 019-2180#BIBL Subspecialty Collections This article, along with others on similar topics, appears in the following collection(s): Sports Medicine/Physical Fitness http://www.aappublications.org/cgi/collection/sports_medicine:physi cal_fitness_sub Concussion http://www.aappublications.org/cgi/collection/concussion_sub Permissions & Licensing Information about reproducing this article in parts (figures, tables) or in its entirety can be found online at: http://www.aappublications.org/site/misc/Permissions.xhtml Reprints Information about ordering reprints can be found online: http://www.aappublications.org/site/misc/reprints.xhtml

Downloaded from www.aappublications.org/news by guest on September 25, 2021 Concussion Incidence and Trends in 20 High School Sports Zachary Y. Kerr, Avinash Chandran, Aliza K. Nedimyer, Alan Arakkal, Lauren A. Pierpoint and Scott L. Zuckerman Pediatrics originally published online October 15, 2019;

The online version of this article, along with updated information and services, is located on the World Wide Web at: http://pediatrics.aappublications.org/content/early/2019/10/11/peds.2019-2180

Pediatrics is the official journal of the American Academy of Pediatrics. A monthly publication, it has been published continuously since 1948. Pediatrics is owned, published, and trademarked by the American Academy of Pediatrics, 345 Park Avenue, Itasca, Illinois, 60143. Copyright © 2019 by the American Academy of Pediatrics. All rights reserved. Print ISSN: 1073-0397.

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