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Archives of Clinical Neuropsychology 34 (2019) 60–69
Incidence and Risk of Concussions in Youth Athletes: Comparisons of
Age, Sex, Concussion History, Sport, and Football Position
William T. Tsushima
1,
*, Andrea M. Siu
2
, Hyeong Jun Ahn
3
, Bolin L. Chang
4
, Nathan M. Murata
5
1
Psychiatry and Psychology Department, Straub Medical Center, Honolulu, Hawaii 96813, USA
2
Research Institute, Hawaii Pacific Health, Honolulu, Hawaii 96813, USA
3
Department of Complementary and Integrative Medicine, John A. Burns School of Medicine, University of Hawaii, Honolulu, Hawaii 96813, USA
4
Department of Biological Sciences, Lehigh University, Bethlehem, PA 18015, USA
5
Department of Kinesiology and Rehabilitation Science, University of Hawaii, Honolulu, Hawaii 96822, USA
*Corresponding author at: Straub Medical Center, 888 South King Street, Honolulu, Hawaii 96813, USA. Tel.: +(808)-522-4521; fax: +(808)-522-3526.
E-mail address: tzking@gsu.edu (W.T. Tsushima).
Editorial Decision 22 January 2018; Accepted 16 February 2018
Abstract
Objective: This study was designed to determine concussion incidence, risk, and relative risk among middle and high school athletes par-
ticipating in various sports.
Method: Data were retrospectively obtained from 10,334 athletes of 12 different sports in Hawaii. In addition to determining the overall
concussion incidence, comparisons of incidence, risk, and relative risk were made according to age, sex, concussion history, sport, and foot-
ball position.
Results: The overall incidence of concussion among youth athletes was 1,250 (12.1%). The relative risk for a concussion was almost two
times greater in 18-year olds than in 13-year-old athletes. In comparable sports, girls had a 1.5 times higher concussion risk than boys.
Athletes with a prior concussion had 3–5 times greater risk to sustain a concussion than those with no history of a concussion. Among var-
ied sports, wrestling and martial arts had the highest relative risk of a concussion, followed by cheerleading, football, and track and field.
No differences in concussion risks were found among the football players in different positions.
Conclusions: Older youths, females, those with a history of concussion, and those participating in high contact sports were found to have
higher risks of sustaining a concussion. The findings increase awareness of concussion patterns in young athletes and raise concerns regard-
ing protective strategies and concussion management in youth sports.
Keywords: Concussion; Risks; Sports; Youth
Introduction
In the past decade, sports-related concussions have drawn considerable attention from the public, the media, state legisla-
tures, and sports medicine. Epidemiological reports provide convincing evidence that numerous concussions occur at all levels
of sport activity (Bakhos, Lockhart, Myers, & Linakis, 2010;Covassin & Elbin, 2011;O’Connor et al., 2017;Stewart,
Gilliland, & Fraser, 2014). Public concern grows as concussion rates (CRs), typically defined as the number of concussions
divided by the number of athlete exposures (AEs) or participation in a practice or competition, have risen in recent years
(Comstock, Curie, & Pierpont, 2017;Lincoln et al., 2011;Zuckerman et al., 2015). The increasing trend may be due to
greater participation in sports and recreation, more concussion education, improved recognition of concussive events, and
new concussion management policies, but also to more concussions due to bigger, stronger, and faster athletes with greater
magnitude of head collisions (Daneshvar, Nowinski, McKee, & Cantu, 2011;Houck et al., 2016). Factors such as age, sex,
concussion history, sport played, and football position appear to be related to the occurrence of sport concussions.
© The Author(s) 2018. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.
doi:10.1093/arclin/acy019 Advance Access publication on 15 March 2018
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Age
Several recent epidemiologic reports of concussions among youth athletes have been published (Lincoln et al., 2011;
Meehan, d’Hemecourt, & Comstock, 2010;O’Connor et al., 2017;Rosenthal, Foraker, Collins, & Comstock, 2014), with
data pertaining to age and varying in content and consistency. Some researchers have found CRs to be higher among high
school athletes than college athletes (Dompier, Kerr, & Marshall, 2015;Shankar, Fields, Collins, Dick, & Comstock, 2007;
Webbe & Barth, 2003), while others indicated higher CRs in college athletes compared to high school athletes (Gessel,
Fields, Collins, Dick, & Comstock, 2007;O’Connor et al., 2017). Reports have variably placed the highest rates of sport-
related traumatic brain injury in the 10–14 year-old age group (Centers for Disease Control and Prevention, 2007;Stewart
et al., 2014), in the 12–14-year-old range (Kontos et al., 2016), in the 14–19 years age range (Bakhos et al., 2010), and in the
15 to 24-year-old range (Thurman, Branche, & Sniezek, 1998). In sum, studies of youth sports concussion reveal varied and
conflicting findings regarding age, probably due to the differences in research methodology.
Sex
In sports medicine literature, CRs have been found generally to be higher in male athletes (Langlois, Rutland-Brown, &
Wald, 2006;Thurman et al., 1998), but in comparable sports females were consistently reported to have a similar or higher
CRs than males (Marar, McIlvain, Fields, & Comstock, 2012;Noble & Hesdorffer, 2013;O’Connor et al., 2017;Rosenthal
et al., 2014). Overall, past studies suggest that CRs are higher in female athletes than males participating in comparable
sports.
Concussion History
Previous investigations have consistently found that individuals with a prior concussion have a greater risk to encounter
another concussion than those who have had no prior concussion. In a longitudinal study of 11,867 head injured children, in-
vestigators found that having a head injury increases the risk of having a subsequent head injury (Swaine et al., 2007).
Similarly, high school athletes with a history of a concussion are more prone to sustain a subsequent concussion than those
who have had no previous concussion (Collins et al., 2002;Schulz et al., 2004). Researchers have found that high school
players who sustain a concussion are 3–6 times more likely to sustain another concussion than those who had not had any
concussion (Guskiewicz, Weaver, Padua, & Garrett, 2000;Zemper, 2003), and that among concussed high school athletes,
10.5% were recurrent (Meehan et al., 2010). A recent epidemiologic study of concussion in seven high school and collegiate
sports found that athletes with a history of one concussion in the previous 24 months had over twice the rate of concussion
compared to those with no prior concussion, and those with two or more previous concussions had a five times higher rate
(Marshall, Guskiewicz, Shankar, McCrea, & Cantu, 2015).
Sport Activities
Studies have found varying CRs across different high school sports. In many reports, the high school sport with the highest
CR is football (e.g., Marar et al., 2012;Noble & Hesdorffer, 2013;O’Connor et al., 2017;Rosenthal et al., 2014), with lower
CRs observed in non-contact sports, such as volleyball, baseball, and swimming. However, a MEDLINE search from
1985–2000 stated that among high school male team sports, ice hockey athletes had the highest CR (3.6 per 1,000 AEs),
while soccer athletes had the lowest CR (0.18 per 1,000 AEs) (Tommasone & Valovich McLeod, 2006). In another report,
CRs were found to be highest in ice hockey and football in 12–17-year olds (Bakhos et al., 2010). Finally, the High School
Reporting Information Online Injury Surveillance System (Comstock, Currie & Pierpoint, 2017) that collects data on 9 sports
from 100 randomly chosen study schools reported that, in the 2015–2016 school year, CRs were highest in girls soccer
(40.5%), girls basketball (31.7%), wrestling (28.3%), and football (27.5%). Overall, the sports medicine literature indicates
that CRs differ among high school sports, reflecting the varying degrees of head impacts inherent in each sport (Harmon
et al., 2013;Koh, Cassidy, & Watkinson, 2003).
Football Positions
Researchers have noted that the position on a team, particularly in football, seems to affect the risk of concussion. Within
high school football, more concussions are found with linebackers and running backs than those in other positions (Gessel
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et al., 2007;Marar et al., 2012), possibly due to their sustaining more frequent collision impacts (Broglio et al., 2011). A
3-year study of 23,566 high school sports-related concussions revealed that the largest proportion of mild traumatic brain inju-
ries occurred among linebackers, running backs, and offensive linemen (Powell & Barber-Foss, 1999). The few available data
on high school football players suggest that more concussions are sustained by linebackers and running backs compared to
other football positions.
A report on sports-related concussion by the Institute of Medicine underlined the need for more comprehensive incidence
data in young athletes (Graham, Rivara, Ford, & Spicer, 2014). To date, there is limited research on the incidence of sports
concussions that occurs across the wide range of youth sports, particularly non-contact sports, like tennis or cross country.
The aim of this study was, first, to determine concussion incidence, risk, and relative risk (RR) among middle and high school
athletes covering a broad spectrum of sports. Epidemiologic reports of sport concussions typically cover the popular sports of
football, basketball, soccer, baseball/softball, volleyball, and wrestling. In addition to these sports, this research examined
other sport activities that are not usually evaluated, that is, cross country, cheerleading, track and field, water polo, and tennis.
Secondly, this research assessed differences in concussion incidences, risks, and RRs across the various sports according to
age, sex, concussion history, sport, and football position.
Method
The 10,334 participants in this research were athletes from schools who represented 67 public and private middle and high
schools in the State of Hawaii. Data for this study were obtained from the Immediate Post-Concussion Assessment and
Cognitive Testing (ImPACT) that athletes underwent prior to their respective sport seasons in the 2013–2014 school year.
ImPACT was administered in groups of 20 or fewer athletes, supervised by certified athletic trainers who were trained to
administer this computerized neuropsychological battery in a standardized manner. Biopsychosocial data yielded by ImPACT
included age, sex, sport played, football position, prior concussion and date of head injury. Approval for the use of the
research data was granted by the State of Hawaii Department of Education. The study was reviewed by the Hawai’i Pacific
Health Research Institute and was determined to be exempt from Institutional Review Board review.
Participants
The subjects for this study were 5,938 males and 4,396 females, grades 8–12. The mean age was 15.5 years (SD =1.3).
Participants included 250 male and 262 female 13-year-olds, 1,295 male and 1,057 female 14-year-olds, 1,414 male and
1,063 female 15-year-olds, 1,456 male and 1,014 female 16-year-olds, 1,148 male and 796 female 17-year-olds, and 375
male and 204 female 18-year-olds.
The number of athletes in the varied sports was football (n=2,724), soccer (n=1,681), volleyball (n=1,202), basketball
(n=1,329), wrestling/martial arts (n=980), baseball (n=532), softball (n=441), cheerleading (n=533), water polo (n=
275), tennis (n=140), track and field (n=137), and cross country (n=126). There were 234 who did not specify the sport
in which they participated.
From a pool of 10,334 participants in this research, 1,250 (12.1%) athletes sustained a concussion during their season.
Concussions were typically observed by the team staff and directly evaluated by the athletic trainer. A minority of athletes
experienced concussive symptoms after a game or practice, and reported their conditions that were assessed by the athletic
trainer. All of the concussed athletes underwent post-injury ImPACT testing. Certified athletic trainers at all of the schools
were available to verify the concussive events, adhering to the criteria provided by the consensus statement on concussion
(McCrory et al., 2013). Athletic trainers, having been certified to identify a concussion, received annual continuing education
through the Hawaii Concussion Awareness and Management Program, a state-funded community program that provides the
Hawaii’s high school sports medical staffs with updated education to recognize and manage school-related sport concussions.
Of the total sample, 8,580 reported having no previous concussion, 1,299 had one previous concussion, 300 had two previous
concussions, and 111 had three or more previous concussions. There were 44 athletes with missing data regarding history of
concussions.
Statistical Analyses
This study calculated concussion incidence, risk, and RRs for age groups, sex, concussion history, sport, and football posi-
tion, with data provided by the Hawaii ImPACT database. Incidence refers to an injury occurring in a practice or competition
requiring attention from an athletic trainer or team physician. In this study, incidence proportion, or risk, reported in
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percentage, was calculated by dividing the number of athletes who incur a concussion during the season by the number of ath-
letes who participated in the sport. Risk is a valid estimate of the probability of injury and is readily understood, but it is less
often used in sports medicine literature because of its difficulty in comparing injury risk in different sports (Knowles,
Marshall, & Guskiewicz, 2006). RR of a concussion was calculated by dividing the concussion risk of a group (e.g., 18 year-
olds) by the risk of a reference or comparison group (e.g., 13-year olds). In addition, adjusted RR (ARR) was calculated via
regression analyses to control for relevant factors, such as age, sex and sport. Ninety five percent confidence intervals (CI)
were generated for RRs and ARRs. Statistical significance was set at p<0.05.
Results
In the varied sports studied over the school year, 1,250 (12.1%) athletes incurred a concussion. Concussion risks were
highest in the 18-year-old range (18.1%) and lowest in the 13-year-old (7.8%) and 14-year-old (7.6%) ranges. The ARR for
concussion, adjusted for sex and sport, for the 18-year olds was found to be nearly two times greater than for 13- and 14-year
olds (ARR =1.91, p=0.0003). Risk, RR, and ARR results, with 13-year olds as the reference group, are shown in Table 1.
In sports played by both sexes, girls had significantly higher concussion risks than boys in three comparable sports: basket-
ball (14.8%), soccer (13.3%), and softball (12.8). The ARR for girls in all sports, including comparable sports, was 1½ times
greater than boys (ARR =1.50, p<0.0001). The risks, RRs, and ARRs, adjusted for age and sport (with boys as the refer-
ence group), are shown in Table 2.
Of the 8,580 who reported no prior concussions, 611 (7.1%) had a concussion during the 2013–2014 school year. Of the
1,299 who reported one prior concussion, 436 (33.6%) had a concussion during the school year. Of the 300 who reported two
prior concussions, 127 (42.3%) received a concussion. Of the 111 who reported three or more prior concussions, 33 (29.7%)
sustained a concussion during the school year. The ARR, adjusted for sex and sport, of those with two self-reported prior con-
cussions was 5.07 times greater than those with no self-reported prior concussion, while athletes with one self-reported prior
concussion had an ARR which was 4.34 times greater than those with no self-reported prior concussion, and those with three
or more self-reported prior concussions had an ARR which was 3.72 times greater than those with no self-reported previous
concussion. The risks, RRs, and ARRs for the self-reported concussion groups, with the no concussion group as the reference,
are presented in Table 3.
From among the various sports, the highest concussion risks were from participation in wrestling/martial arts (20.8%), fol-
lowed by cheerleading (15.9%), and football (15.4%). The lowest risks were in cross country (3.2%), tennis (3.6%), and water
polo (4.0%). Table 4shows the risks, RRs, and ARRs by sports, adjusted for age and sex, with cross country as the reference
group. Wrestling and martial arts obtained ARRs that were 6.07 times greater than cross country, followed by football (5.68)
and track and field (4.24). Lowest ARR ratios were in water polo (1.00), tennis (1.10), and volleyball (1.35).
Among football players, the highest concussion risks were seen in running backs (18.9%), followed by defensive backs
(16.7%), and kickers (15.8%). Lowest risks were found to be with linebackers (13.4%) and defensive linemen (13.9%). With
linebackers as the reference group, running backs had an ARR, adjusted for age, that was 1.43 times greater than linebackers,
followed by defensive backs (1.26) and offensive linemen (1.16). The lowest ARR was seen in kickers (1.06). The risks,
RRs, and ARRs of the football positions are shown in Table 5.
Discussion
This large-scale research involving 10,334 middle and high school athletes offered a unique opportunity to examine the
incidence of concussions occurring during a single season of a wide variety of high school sports. While there are different
Table 1. Risk, RR, and adjusted RR by age
Age Number of athletes Number of concussions Risk (%) RR Adjusted RR
a
(95% CI) ARR p-value
13 512 40 7.8 Reference Reference NA
14 2,352 178 7.6 0.97 (0.70, 1.35) 0.82 (0.59, 1.15) 0.248
15 2,477 363 14.7 1.88 (1.37, 2.56) 1.53 (1.11, 2.11) 0.009**
16 2,470 309 12.5 1.60 (1.17, 2.19) 1.32 (0.96, 1.83) 0.089*
17 1,944 255 13.1 1.68 (1.22, 2.31) 1.39 (1.01, 1.93) 0.046*
18 579 105 18.1 2.32 (1.65, 3.28) 1.91 (1.35, 2.71) 0.0003**
a
Adjusted for sex and sport.
*p<0.05. **p<0.01.
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ways to report concussion data, we chose to examine concussion incidence in terms of risk, or the percent of athletes on a
team who sustained a concussion during the season. Risk indicates the probability of a concussion per athlete and is a valid
estimator of the chance of a concussion. Risk is less often employed in sports medicine research that typically reports CRs
based on athletic exposure, that is, number of games and practices, and is less applicable when comparing concussion in dif-
ferent sports that have varying amounts of games and practices (Knowles et al., 2006). The advantage of the risk data is that
they are more useful for risk assessment and may be more readily interpretable than CRs that require understanding the con-
cept of the person-time in AEs. The present investigation reported risks, RRs, and ARRs of concussion among varied sports
according to age, sex, concussion history, sport, and football position, expanding the understanding of youth sports
concussion.
Table 2. Risk, RR, and adjusted RR by sex and sport
Number of
athletes
Number of
concussions
Risk
(%)
RR Adjusted RR
a
(95% CI)
ARR
p-value
All sports
Male 5,938 719 12.1 Reference Reference
Female 4,396 531 12.1 1.00 (0.90, 1.11) 1.50 (1.29, 1.73) <.0001**
All comparable sports
Male 2,974 292 9.8 Reference Reference
Female 3,603 434 12.1 1.23 (1.07, 1.41) 1.50 (1.29, 1.74) <.0001**
Comparable Sports
Soccer
Male 711 55 7.7 Reference Reference
Female 970 129 13.3 1.72 (1.27, 2.32) 1.75 (1.30, 2.38) 0.0003**
Basketball
Male 701 64 9.1 Reference Reference
Female 628 93 14.8 1.62 (1.20, 2.19) 1.62 (1.20, 2.19) 0.0018**
Volleyball
Male 226 6 2.7 Reference Reference
Female 976 54 5.5 2.08 (0.91, 4.78) 2.21 (0.96, 5.09) 0.0626
Wrestling/martial arts
Male 636 123 19.3 Reference Reference
Female 344 81 23.5 1.22 (0.95, 1.56) 1.19 (0.93, 1.53) 0.1691
Baseball/ Softball
Male 525 34 6.5 Reference Reference
Female 438 56 12.8 1.97 (1.31, 2.97) 2.07 (1.38, 3.11) 0.0004**
Water polo
Male 102 2 2 Reference Reference
Female 173 9 5.2 2.65 (0.58, 12.04) 2.04 (0.44, 9.41) 0.3611
Tennis
Male 56 2 3.6 Reference Reference
Female 84 3 3.6 1.00 (0.17, 5.79) 1.04 (0.18, 6.00) 0.9676
Track & field
Male 70 8 11.4 Reference Reference
Female 67 12 17.9 1.57 (0.68, 3.59) 1.66 (0.73, 3.80) 0.2269
Cross country
Male 71 3 4.2 Reference Reference
Female 55 1 1.8 0.43 (0.05, 4.02) 0.45 (0.05, 4.17) 0.4792
a
Adjusted for age.
**p<0.01.
Table 3. Risk, RR, and adjusted RR by concussion
Concussion group Number of athletes Number of concussions Risk (%) RR Adjusted RR
a
(95% CI) ARR p-value
0 8,580 611 7.1 Reference Reference NA
1 1,299 436 33.6 4.71 (4.23, 5.25) 4.34 (3.89, 4.83) <0.0001**
2 300 127 42.3 5.95 (5.10, 6.92) 5.07 (4.37, 5.88) <0.0001**
3+111 33 29.7 4.18 (3.11, 5.61) 3.72 (2.79, 4.97) <0.0001**
a
Adjusted for sex and sport.
**p<0.01.
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This research found that, from among the 10,334 athletes, 1,250 (or 12.1%) sustained a concussion during the school year.
This finding is lower than the 16.7% incidence proportion noted in a prospective 11-year study of concussion incidence in
high school sports by Lincoln et al. (2011). Differences in research methodology may account for the contrasting results. The
Lincoln epidemiological research employed an electronic medical record-keeping program on a daily basis as contrasted with
the retrospective data collection in this investigation. The different sports evaluated in the two studies could have also influ-
enced the variable results. In this study, concussions were found to occur more frequently with older high school athletes,
female athletes, players with a prior history of concussion, and athletes who participate in wrestling and martial arts.
Age
The findings of this study indicated that older student athletes, that is, 18-year olds, have a much higher incidence of concus-
sions compared with younger student athletes, that is, 13-year olds. RR and ARR data showed that 18-year-old athletes have
about twice the risk of sustaining a concussion compared to 13-year olds. These results are noteworthy in that, to our knowledge,
no study has examined concussion risks in specific ages of youth athletes. Older youth athletes may suffer more concussions as
they may have more playing time, are bigger and stronger, and play at a faster, more intense and competitive level that could
increase the risk of severe impacts and concussion (Gessel et al., 2007). Some older athletes may have sustained a concussion
earlier in their school years, thus increasing their risk of concussions in subsequent head injuries (Zemper, 2003).
This research highlights the need for additional studies into the age factor in youth sports concussions, especially for the older stu-
dent athlete. Concussion data pertaining to middle school and grade school athletes are rare, calling for more research in these younger
age groups, who receive less professional medical attention than college and professional athletes (Halstead & Walter, 2010).
Sex
The present study found higher concussion risks in female youth athletes when compared to males over a wide range of
comparable sport activities. In certain sports, such as basketball, soccer, and softball, female athletes had over 1.5–2 times the
Table 5. Risk, RR, and adjusted RR by football position
Position Number of athletes Number of concussions Risk (%) RR Adjusted RR
a
(95% CI) ARR p-value
Running back 196 37 18.9 1.41 (0.94, 2.12) 1.43 (0.95, 2.14) 0.09
Defensive back 365 61 16.7 1.25 (0.87, 1.80) 1.26 (0.87, 1.81) 0.22
Kicker 19 3 15.8 1.18 (0.40, 3.46) 1.06 (0.36, 3.12) 0.92
Offensive lineman 279 43 15.4 1.15 (0.77, 1.71) 1.16 (0.78, 1.73) 0.46
Quarterback 113 16 14.2 1.06 (0.62, 1.81) 1.07 (0.63, 1.83) 0.79
Receiver 487 69 14.2 1.06 (0.74, 1.51) 1.08 (0.75, 1.55) 0.67
Defensive lineman 366 51 13.9 1.04 (0.71, 1.52) 1.04 (0.71, 1.52) 0.84
Linebacker 306 41 13.4 Reference Reference NA
a
Adjusted for age.
Table 4. Risk, RR, and adjusted RR by sport
Sport Number of athletes Number of concussions Risk (%) RR Adjusted RR
a
(95% CI) ARR p-value
Wrestling/martial arts 980 204 20.8 6.56 (2.48, 17.33) 6.07 (2.30, 16.02) 0.0003**
Cheerleading 533 85 15.9 5.02 (1.88, 13.44) 3.99 (1.49, 10.70) 0.0059**
Football 2,724 420 15.4 4.86 (1.84, 12.79) 5.68 (2.15, 14.98) 0.0005**
Track and field 137 20 14.6 4.60 (1.62, 13.09) 4.24 (1.49, 12.04) 0.0067**
Softball 441 56 12.7 4.00 (1.48, 10.82) 3.28 (1.21, 8.89) 0.0193*
Basketball 1,329 157 11.8 3.72 (1.40, 9.87) 3.52 (1.33, 9.32) 0.0114*
Soccer 1,681 184 10.9 3.45 (1.30, 9.13) 3.11 (1.18, 8.23) 0.0223*
Baseball 532 34 6.4 2.01 (0.73, 5.57) 2.39 (0.86, 6.61) 0.0945
Volleyball 1,202 60 5 1.57 (0.58, 4.25) 1.35 (0.50, 3.67) 0.5518
Water polo 275 11 4 1.26 (0.41, 3.88) 1.00 (0.32, 3.12) 0.9998
Tennis 140 5 3.6 1.13 (0.31, 4.10) 1.10 (0.30, 3.99) 0.8868
Cross country 126 4 3.2 Reference Reference NA
a
Adjusted for age and sex
*p<0.05. **p<0.01.
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RR and ARR of a concussion than males. A literature review of sex difference in sport concussion in high school, college,
and professional levels likewise showed higher CRs for females compared to males in similar sports (Dick, 2009), a pattern
that has been noted in several previous studies of high school athletes (Lincoln et al., 2011;Marar et al., 2012;Rosenthal
et al., 2014). Possible explanations for sex differences in concussion patterns are limited, with some suggesting biomechanical
(body mass, small head-to-ball ratio, neck strength), neuroanatomical, or hormonal factors underlying female concussions
(Covassin, Swanik, & Sachs, 2003;Strand, Lechuga, Zachariah, & Beaulieu, 2015). Psychosocial influences may lead males
to minimize injuries, play despite injury and underreport symptoms in order to continue to play (Kerr, Register-Mihalik,
Kroshus, Baugh, & Marshall, 2016). Along with prior findings that female athletes exhibit more neuropsychological decline
than males following sports-related concussion (Broshek et al., 2005;Covassin, Elbin, Harris, Parker, & Kontos, 2012), the
present results call for further research regarding concussion risks and prevention strategies in female youth athletes.
Prior concussion
One of the significant findings in this report is that youth athletes who report having a prior concussion are three to five
times more likely to sustain a concussion during the school year than athletes without a reported history of concussion. The
athletes with one self-reported prior concussion had an ARR that was over four times greater than those with no self-reported
prior concussions. The ARR for athletes with two self-reported prior concussions was five times greater than those with no
self-reported previous concussion, and for those with three or more self-reported prior concussion was more than three times
greater than those who had no self-reported prior concussion. The data do not support a dose–response relationship between
the number of self-reported concussions and subsequent concussive events.
A mild brain trauma results not only in immediate physiological changes but may affect neuronal plasticity and increase
the risk for a subsequent concussion (Giza & Hovda, 2001;Noble & Hesdorffer, 2013). Thus, the capacity of the brain of pre-
viously concussed athletes to respond to another head trauma may be compromised and is, therefore, more susceptible to a
subsequent concussion. It has also been proposed that high school athletes who had a prior concussion may be the more expe-
rienced players who participate more in games and practices and are more likely to have another concussion because of
greater exposure to play activity (Schulz et al., 2004). The present findings are consistent with observations by previous inves-
tigators (Collins et al., 2002;Guskiewicz et al., 2000), and have important implications for the proper management of head
injured young athletes (Gavett, Stern, & McKee, 2011;Graham et al., 2014;Harmon et al., 2013).
Sports
More concussion incidents seem to occur in certain sports. The highest percentage of concussions and ARRs was seen in
wrestling and martial arts, followed by cheerleading and football. While many studies of high school sports have consistently
found football to have the highest CRs among the varied sport activities (Lincoln et al., 2011;Marar et al., 2012;Noble &
Hesdorffer, 2013;Rosenthal et al., 2014;Shankar et al., 2007), wrestling and cheerleading have also been noted to have high
concussion risks (Comstock et al., 2017;Stewart et al., 2014). In previous studies of CRs, participants in wrestling and cheer-
leading have not been identified among those with the highest CRs, most likely because of their lower exposure to sport activ-
ity, compared with football or ice hockey. Instead of risk data, most previous comparisons of sports have employed CRs that
take into account AE, or total person-time at risk, which is considered to be the most appropriate way to compare different
sports (Knowles et al., 2006), but was not available for this study.
Football positions
None of the ARRs comparing the different football positions, with linebackers as the reference, was statistically significant.
The lack of differences between the varied football positions may be attributed to the youth athletes playing in more than one
position or playing on offense and defense.
Limitations
In this research, concussions that occurred during the school year were documented by a certified athletic trainer, but the
history of prior concussions was obtained by the self-report of the athlete. The actual number of self-reported concussions is
likely underestimated due to the failure of accurate documenting of head injuries by young athletes and support staff (Kerr
et al., 2016;Williamson & Goodman, 2006). Reasons for the underreporting of concussions include the athlete’s unawareness
66 W.T. Tsushima et al. / Archives of Clinical Neuropsychology 34 (2019); 60–69
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of having sustained a concussion, minimizing the seriousness of the head blow, and deliberately not reporting a concussion so
as to avoid being withheld from participating.
The participants in this study were a convenience sample enrolled in schools in Hawaii, with results that could assist in
region-specific efforts to improve concussion education and increase player safety. However, our results may not be generaliz-
able to schools in other geographic locations and with different sociocultural representation. The gathering of similar risk inci-
dence data from other regions in the country could enhance the generalizability of these findings. Although this research
examined 12 different sports in Hawaii, it did not include other sports that are associated with high risks of concussion in
other states and countries, such as hockey, lacrosse, and rugby.
The athletes in this study were identified as participating in one sport, but youth athletes often play in multiple sports. If an
identified football player sustained a concussion in baseball but not in football, he was counted as a baseball player who had a
concussion and also counted as football player who did not have a concussion. However, we do not know how many athletes
who did not suffer any concussion played in more than one sport. Limitations should be recognized regarding the retrospec-
tive nature of this study that lacked a systematic method for tracking athletes who sustained a concussion, with unknown in-
tervals between the occurrence of a concussion and its reporting. The present data did not include the circumstances of the
head injuries, for example, whether a concussion was due to head-to-head, head-to-body, or ground contact, and did not dif-
ferentiate a concussion sustained in practice or in a game. Finally, our findings provide no clear understanding of factors,
such as age and sex, which may predispose an athlete to a concussion.
Conclusion
While the interest in sports-related concussion is often focused in major collision sports, like football, the present study,
through a large sample of high school athletes, provides information about the incidence and risk of concussion across a wide
spectrum of team and individual sports. Our findings show that concussion risks vary considerably by age, sex, concussion
history, and sport. Reporting concussion incidence and risk rates have intrinsic informative value for athletes, parents, coa-
ches, and athletic staff. The present findings increase our knowledge and understanding of concussion patterns in high school
athletes in various sports that can enhance protective and preventative strategies with these young participants.
Funding
HJA was partially supported by grant U54MD007584 from the National Institute on Minority Health and Health
Disparities. The content is solely the responsibility of the authors and does not necessarily represent the official views of the
NIH.
Conflict of interest
None declared.
Acknowledgements
The ImPACT data were provided by the Hawaii Concussion Awareness and Management Program (HCAMP). The authors
thank the Hawaii State Department of Education for their support, and the certified athletic trainers who submitted the data to
HCAMP. The fourth author, BLC, participated in the Hawaii Pacific Health Summer Student Research Program while he as-
sisted in this research project.
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