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Powell JW, Barber-Foss KD. Traumatic Brain Injury in High School Athletes. JAMA. 1999;282(10):958–963. doi:10.1001/jama.282.10.958
Author Affiliations: Med Sports Systems, Iowa City, Iowa. Dr Powell is now with the Department of Kinesiology, Michigan State University, Lansing.
Context The potential seriousness of mild traumatic brain injury (MTBI) is increasingly
recognized; however, information on the frequency of MTBI among high school
athletes is limited.
Objective To identify the type, frequency, and severity of MTBI in selected high
school sports activities.
Design Observational cohort study.
Setting and Participants Two hundred forty-six certified athletic trainers recorded injury and
exposure data for high school varsity athletes participating in boys' football,
wrestling, baseball and field hockey, girls' volleyball and softball, boys'
and girls' basketball, and boys' and girls' soccer at 235 US high schools
during 1 or more of the 1995-1997 academic years.
Main Outcome Measures Rates of reported MTBI, defined as a head-injured player who was removed
from participation and evaluated by an athletic trainer or physician prior
to returning to participation. National incidence figures for MTBI also were
Results Of 23,566 reported injuries in the 10 sports during the 3-year study
period, 1219 (5.5%) were MTBIs. Of the MTBIs, football accounted for 773 (63.4%)
of cases; wrestling, 128 (10.5%); girls' soccer, 76 (6.2%); boys' soccer,
69 (5.7%); girls' basketball, 63 (5.2%); boys' basketball, 51 (4.2%); softball,
25 (2.1%); baseball, 15 (1.2%); field hockey, 13 (1.1%); and volleyball, 6
(0.5%). The injury rates per 100 player-seasons were 3.66 for football, 1.58
for wrestling, 1.14 for girls' soccer, 1.04 for girls' basketball, 0.92 for
boys' soccer, 0.75 for boys' basketball, 0.46 for softball, 0.46 for field
hockey, 0.23 for baseball, and 0.14 for volleyball. The median time lost from
participation for all MTBIs was 3 days. There were 6 cases of subdural hematoma
and intracranial injury reported in football. Based on these data, an estimated
62,816 cases of MTBI occur annually among high school varsity athletes participating
in these sports, with football accounting for about 63% of cases.
Conclusions Rates of MTBI vary among sports and none of the 10 popular high school
sports we studied is without the occurrence of an MTBI. Continued involvement
of high school sports sponsors, researchers, medical professionals, coaches,
and sports participants is essential to help minimize the risk of MTBI.
High school students who choose to participate in sports place themselves
at risk for a sports-related injury.1 An important
area for concern is injury that may result from a rotational or linear force
applied to the head and brain from a direct impact or indirect force (ie,
acceleration/deceleration).2 These forces may
result in a minimal injury to the brain or may cause permanent disability
The term concussion previously was defined
as "a clinical syndrome characterized by immediate and transient posttraumatic
impairment of neural function, such as alteration of consciousness and disturbance
of vision or equilibrium due to brain-stem involvement."3
In recent literature, concussion has been defined as a trauma-induced alteration
in mental status that may or may not involve a loss of consciousness.4,5 Recently, the terms mild head injury, traumatic brain injury,
or mild traumatic brain injury (MTBI) have been used
to describe brain injuries.2,6,7
The definitions of these terms include a review of the signs and symptoms
and the loss of consciousness and amnesia. In this article we use MTBI to
describe injuries for which the injured player was removed from participation
and evaluated for a traumatic brain or head injury by the athletic trainer,
physician, or both, prior to returning to participation.
In this study, we examined the frequency patterns for MTBI that are
associated with participation in 10 selected high school sports: football,
boys' and girls' basketball, boys' and girls' soccer, wrestling, field hockey,
baseball, softball, and girls' volleyball.
This study used data from the National Athletic Trainer Association
(NATA) injury surveillance program, which was designed to assess the impact
that sport-related risk factors have on the incidence of injuries among high
school varsity athletes. Data recording materials were designed to use the
strengths of the National Athletic Injury/Illness Reporting Systems, the 1986-1988
NATA study and injury surveillance systems in place for the National Collegiate
Athletic Association, the National Football League, and the National Hockey
From the 350 NATA-certified athletic trainers who volunteered to participate
in the project, 246 were selected to participate. For athletic trainers to
participate, they had to (1) work directly with high school sports programs
on a daily basis, (2) work within a geographic distribution among the 50 states,
and (3) fit a broad representation from different-sized schools within the
various parts of the country. These procedures created a stratified cluster
sample representing high schools with different-sized student enrollments.
The distribution of the NATA study sample by size of school enrollment
was similar to size of school distribution reported by the National Center
for Education Statistics in 1994.10 Compared
with National Center for Education Statistics data, the study had less representation
in schools with enrollments of fewer than 500 (11.9% vs 15.3%) and 500 to
1000 (20% vs 30.2%), higher representation in schools with enrollment of 1001
to 1500 (31.9% vs 24.7%) and 1501 vs 2000 (22.6% vs 14.5%), and similar representation
for schools with more than 2000 students (13.6% vs 14.4%).
A total of 114 high schools participated for 3 years of the study, 42
recorded data for 2 of the 3 school years, and 79 (27 in 1995, 20 in 1996,
and 32 in 1997) contributed complete data for only 1 school year. Because
not all schools offered all 10 sports, the number of team-seasons (1 team
in 1 season) for each sport varied. For the majority of schools, 1 athletic
trainer recorded data for all sports. As new athletic trainers entered the
study, special emphasis was given to them to provide a smooth transition into
the recording process and the system requirements.
The subjects in the study are athletes who were included as participants
on the varsity sports rosters at the study schools. No effort was made to
manipulate or control the athlete's participation in sports. All references
to the player's data that were submitted to the research office were coded
by the participating athletic trainers so that the player could not be identified.
The project did not place players at risk, but only observed and recorded
the experiences of this population of athletes as they participated in their
chosen sport. The certified athletic trainers were required to submit to the
research office a written permission to participate statement from their school's
athletic director prior to submitting data.
Prior to the beginning of the study, the operational definitions and
reporting requirements were included in a user's manual and distributed to
all athletic trainers. Data were recorded by the athletic trainers using a
customized version of the Sports Injury Monitoring System (Med Sports Systems,
Iowa City, Iowa) and were transferred to the central database using manual
or electronic procedures. Schools without access to computers provided data
using paper forms that paralleled the software. All reported data were subject
to specific procedures for verification. Data collected included player height,
weight, age; type of session (game or practice); number of participants; player
position and player activity; team activity; playing surface at the time of
injury; and time lost from participation.
A reportable injury in the NATA study included an incident that caused
cessation of customary participation in the current session (game or practice)
or on the day following the day of injury onset. A reportable injury was also
any fracture or dental injury that occurred, even though the athlete might
not have missed a scheduled session.
A reportable MTBI in the NATA study was identified by the certified
athletic trainer when the injury required the cessation of a player's participation
for initial observation and evaluation of the injury signs and symptoms before
returning to play, either in the current session or subsequent sessions. By
using this definition of MTBI, athletic trainers were able to report cases
that they observed or were reported to them for which they conducted an evaluation
for MTBI. Athletic trainers were not asked to grade the injury, but only to
report that the player's participation was suspended while an evaluation for
MTBI was conducted.
The days lost from participation following an MTBI was used as an indicator
of the relative effect the injury had on the player's participation in sports.
Players were classified as having injuries that resulted in loss of participation
for fewer than 8 days, between 8 and 21 days, or more than 21 days.1,8,9,11,12
Injury rates per 100 player-seasons reflect the number of injuries reported
divided by the number of players who were subjects in the study. Using the
case rates per 100 player-seasons, the individual season data were statistically
tested to determine if the year of recording showed variation in the injury
rates.13 The results identified homogeneity
among the seasons for each sport. The 95% confidence intervals for the injury
rates were calculated using statistical software(EpiCalc 2000, Version 1.0,
Brixton Health, Llanidloes, Powys, Wales) using methods described by Kirkwood.14
Athlete exposure or opportunities for injury are calculated by aggregating
the number of participants for each game or practice. For example, 100 players
in each of 5 practices would equal 500 athlete exposures. Only those persons
who played in the game accumulated game exposures. Injury rates for the aggregate
of the 3 study years are compared with a reference base of 1000 athlete exposures.
The incidence density ratio (IDR) was used to compare injury rates among
sports and within the conditions of the sport. The IDR was based on the injury
rates per 1000 athlete exposures and used as an estimate of the relative risk
of injury. For example, the IDR that compares practices and games was calculated
by dividing the injury rate in games by the injury rates for practice and
describes the relative risk of injury for games compared with practices. To
test the null hypothesis of no difference between the 2 injury rates, a procedure
that uses a standard normal approximation to the binomial distribution was
used.15 Test-based 95% confidence intervals
were calculated according to the methods of Miettinen.16
Subdural hematoma and episodes of intracerebral bleeding are included
in the patterns of injury and removed from the analysis when time lost consideration
is presented. These more serious brain injuries are described separately.
To estimate national incidence of MTBI in these 10 sports, the number
of players in the United States was estimated from the participation data
obtained from the National Federation of State High School Association's handbooks
for 1995, 1996, and 1997. The Federation estimates that its records account
for approximately 89% of US high school participants. For this study, the
US participation numbers were estimated by dividing the National Federation
of State High School Association data by 0.89. The incidence estimates were
calculated by multiplying the injury rate per player times the estimated number
For the 10 high school sports we studied during the 1995, 1996, and
1997 academic years, the NATA project documented 74,298 player-seasons from
3195 team-seasons, 23,566 reportable injuries, and more than 4.4 million opportunities
to be injured (athlete exposures). Of the reported injuries, 1219 (5.5%) were
MTBIs. The median time loss for reported MTBI was 3 days. In 89% of the cases,
the injured player was removed from the session and 54.8% of the injured players
were referred to a physician, medical clinic, or hospital for additional evaluation.
(The findings of these medical evaluations are not included in this study.)
Data on rates of MTBI for the 10 study sports are shown in Table 1 and Table 2.
Of all sports, football had the highest number and rates of MTBI (Table 1). Injury rates were 11 times higher
(IDR, 11.4) for games than for practice. The conditions surrounding the tackle,
either tackling or being tackled, accounted for the greatest frequency for
MTBI in both practices (61.1%) and games (63.5%). The median time lost due
to an MTBI was 3 days.
The largest proportions of MTBIs occured among linebackers (14.3%),
running backs (14.0%), and offensive linemen (13.4%). The highest injury rate
per 100 team-game positions (ie, the number of team games multiplied by the
number of players in the various positions [1 quarterback, 1 tight end, 2
running backs, 2 wide receivers, 3 linebackers, 4 defensive linemen, 5 offensive
linemen]) was for the quarterback (1.3) compared with running backs (0.74)
and linebackers (0.52).
During the study, 693 different players sustained an MTBI while playing
football, including 621 (89.6%) who sustained only 1 injury, 65 players who
had 2 MTBIs, 6 players who had 3 MTBIs, and 1 player who had 4 MTBIs. Of the
72 players who were reinjured, 47 had a second MTBI in the same season and
14 had a second MTBI in the next season. One person had 3 MTBIs in 1 season
and 1 person had 4 MTBIs in 1 season. There were 4 cases of subdural hematoma
and 2 cases of intracerebral bleeding reported in the 3 seasons of football
and none in any of the other sports. Of these 6 players, 3 returned to football
the following season and 3 did not but did return to participate in other
types of sports and physical activities. There were no deaths.
More than half of the cases of MTBI in wrestling (53%) occurred during
practices. The injury rate for MTBI in matches is 3.1 times higher than practice
sessions. The MTBI cases were fairly evenly distributed among the various
weight classes for both matches and practices. Player activity most often
associated with MTBI was the takedown or attempted takedown both in practice
(64.6%) and in matches (70.0%). During the 3 study years, 115 different players
sustained an MTBI, and 11 players had a second MTBI. The median time lost
due to an MTBI was 2 days.
Games accounted for 62.8% of the reported MTBIs in boys' basketball,
with an IDR 4.9 times the MTBI injury rate for games compared with practices.
The MTBI occurred most often as a result of collisions between players in
both practices (42.1%) and games (53.1%). Players designated as guards accounted
for 62.5% of the game-related MTBIs whereas forwards sustained 68.4% of the
practice-related MTBIs. The median time lost due to an MTBI was 2 days. There
were 51 different players who sustained an MTBI. One person sustained an MTBI
in 1 season followed by 1 in the next season.
In girls' basketball, 68.3% of MTBIs occurred in games with an IDR 6.1
times the injury rate for practices. The injury pattern shows MTBIs occurring
in guards accounting for 56.4% of the game-related cases with 62.5% of practice-related
MTBIs occurring in forwards. In games, 41.3% of the MTBIs occurred during
rebounding and 46.5% of the cases resulted from collisions with players. The
median time lost due to an MTBI was 2 days. Fifty-nine different players sustained
an MTBI, and 4 players sustained a second episode.
Boys' soccer games accounted for 85.5% of the injuries and the injury
rate was 16.2 times greater for a game than a practice. Players on the forward
line and the halfbacks sustained 66.1% of the injuries and the goalkeeper
accounted for 11.9% of MTBIs. The MTBI most often occurred from collisions
while heading the ball (59.3%). The second most frequent cases of MTBI occurred
from collisions with other players (30.5%). The median time lost due to an
MTBI was 3 days. There were 67 different players who sustained an MTBI and
2 sustaining a second occurrence.
For girls' soccer, games had an IDR 14.4 times higher than practice
sessions. Players on the forward line and the halfbacks had 70.3% of the injuries
and the goalkeeper accounted for 18.8% of the MTBI cases. The MTBI most often
occurred from collisions while heading the ball (40.6%) and from collisions
with other players (42.2%). The median time lost due to an MTBI was 3 days.
Sixty-seven players sustained an MTBI and 9 players sustained a second episode.
Of the 9 reinjured players, 5 were reinjured in the same season, 1 was reinjured
in the next season, and 3 were reinjured 2 seasons after the first MTBI.
The baseball game injury rate was 4.5 times higher than for practice.
Among the 15 MTBIs, 9 occurred from collisions between players, 3 from collisions
with a bat, 2 from being hit by a pitch, and 1 from sliding. The median time
lost due to an MTBI was 3 days with 53.3% of the MTBI cases requiring fewer
than 8 days and none requiring more than 21 days to return to participation.
In the 3 seasons, 15 different players sustained an MTBI.
Among the 25 MTBIs in girls' softball, 13 occurred as a result of collisions
with other players. There was 1 MTBI from being hit with a bat and 2 from
being hit by a batted ball. Six MTBIs occurred from collisions during a sliding
activity and 3 MTBIs occurred from being hit by a pitch. The median time lost
due to an MTBI was 2 days. Twenty-three different players sustained an MTBI
with 2 players being reinjured.
Games had an injury rate 14.4 times higher than practices. Of the 13
cases of MTBI, 4 occurred from being hit with a stick and 4 occurred from
being hit with a ball. The remaining 5 cases resulted from collisions with
other players. The median time lost due to an MTBI was 3 days. There were
12 different players injured with 1 person sustaining a second MTBI.
Four of the 6 MTBI cases reported in volleyball occurred in practice
and 2 in games. Collision with a ball accounted for 3 cases, digging for 2
cases, and collision with a player for 1 case. The median time lost due to
an MTBI was 1 day. Six different players sustained an MTBI in 3 seasons.
The annual national estimate of MTBIs among the 10 high school sports
is 62,816 cases, with football accounting for nearly 63% of the injuries (Table 3). Based on the frequency reported
in the NATA study and the number of participating teams, the expected number
of cases of MTBI per team per season is projected in Table 3. For instance, a football team can expect an average of
2 MTBI cases per year, whereas in volleyball, 2 cases of MTBI in 100 team-seasons
Recent research efforts have begun to investigate the incidence, prevalence,
and management of MTBIs. For example, the National Football League (Elliot
Pellman, MD, oral communication, September 1998) and the National Hockey League
(Charles Burke, MD, oral communication, September 1998) have initiated projects
to document the natural history of MTBI. Other programs include systematic
sideline evaluation procedures,17 neuropsychological
measurements to assess the head-injured player's ability to process information,18 biomechanical studies of balance as an evaluation
tool,19 and the neurobiology of the MTBI.20 Incidence data are important in designing research
programs and for evaluating the success of intervention programs.
The data in the current study are limited to injuries, specifically
MTBIs that were reported by NATA-certified athletic trainers who were on-site
at the study schools on a daily basis. Within this group of certified athletic
trainers, 55% had graduate degrees and 73% were employed as full-time members
of the school's faculty.
The definition used to record incidence data will change the frequency
of reported cases and the magnitude of estimated injury. While the athletic
trainer did not question every player after every session, we assume that
events reported to or observed by the athletic trainer were reported in the
Gerberich et al21 estimated the magnitude
of concussions in high school football in the late 1970s and found an injury
rate of 19 concussions per 100 players with 24% of all injuries listed as
concussions. These injuries occurred prior to the implementation of the National
Operating Committee for Safety in Athletic Equipment helmet protection standards
in 1980, which may have an impact on their injury rates compared with current
football injuries nearly 20 years after the introduction of the rule. In a
prospective study of college football players from 1982 through 1986, Barth
et al2 found 195 injuries among 182 different
players in a population of 2350 athletes; 7.7% of the study group had sustained
a reportable mild head injury. In our study using NATA data, 693 athletes
(3.9%) had MTBIs in a population of 17,815 athletes. The difference may reflect
differences in the population (college vs high school), the period (1982-1986
vs 1995-1997), the study design, and mechanisms of documentation. McCrea et
al17 recently reported 33 concussions (5.8%)
among a group of 353 high school and 215 college football players. The article
also reports high school data for 1995 as 6 concussions in 141 players (4.3%),
which is comparable with the current study at 3.9%.
The findings of our study highlight the importance of collisions, in
all forms, as a contributing factor for MTBI in sports. Football, a sport
characterized by collisions, compared with girls' volleyball represent opposite
ends of the continuum. In basketball, the collisions seem to occur between
players in the open court not necessarily under the basket. In soccer, the
collisions occur between players and during heading of the ball. However,
the current data are unable to clearly differentiate an MTBI from head-to-ball
contact vs head-to-body or ground contact during the heading process. The
data on field hockey point to collisions with objects, such as the stick or
the ball, as well as player collisions as risk factors. The potential for
collision among players as well as with bats and balls is low in baseball
and softball. Even with the low potential, there are MTBIs that result from
Given the close association of MTBI with a variety of different types
of collisions, prevention strategies may be most successful when interventions
are aimed at controlling the participation environment. Modifications in player
skills, teaching techniques, and playing rules may be required to reduce the
potential risk from different types of collisions in sports. In addition,
sports medicine professionals should focus on accurate identification of MTBIs
and consistent management throughout the recovery period. Players and coaches
must be encouraged to report all suspected head injuries to athletic trainers
and team physicians.
Clearly identifying the MTBI, carefully documenting the signs and symptoms
at the time of injury, reevaluation of the signs and symptoms until they disappear,
and monitoring of brain function through neuropsychological profiles may lead
to greater success in prevention of reinjury. While not all MTBIs can be prevented,
accurate and consistent medical management of those that occur will minimize
the potential for reinjury and subsequently reduce the potential for the long-term
effects that have been associated with MTBI. Modifications of player skills,
rule changes, and protective equipment can only go so far in the prevention
of MTBI. Only through the continued cooperation of sports sponsors, researchers,
medical professionals, coaches, and sports participants can the goal of minimizing
the risk of MTBI and its long-term disability be achieved.
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