ORIGINAL RESEARCH

Unreported Concussion in High School Football Players

Implications for Prevention

Michael McCrea, PhD, Thomas Hammeke, PhD, Gary Olsen, MS, Peter Leo, BS, and

Kevin Guskiewicz, ATC, PhD

Objective:

To investigate the frequency of unreported concussion

and estimate more accurately the overall rate of concussion in high

school football players.

Design:

Retrospective, confidential survey completed by all subjects

at the end of the football season.

Setting and Participants:

A total of 1,532 varsity football players

from 20 high schools in the Milwaukee, Wisconsin, area were sur-

veyed.

Main Outcome Measurements:

The structured survey assessed

(1) number of concussions before the current season, (2) number of

concussions sustained during the current season, (3) whether concus-

sion during the current season was reported, (4) to whom concussion

was reported, and (5) reasons for not reporting concussion.

Results:

Of respondents, 29.9% reported a previous history of con-

cussion, and 15.3% reported sustaining a concussion during the cur-

rent football season; of those, 47.3% reported their injury. Concus-

sions were reported most frequently to a certified athletic trainer

(76.7% of reported injuries). The most common reasons for concus-

sion not being reported included a player not thinking the injury was

serious enough to warrant medical attention (66.4% of unreported

injuries), motivation not to be withheld from competition (41.0%),

and lack of awareness of probable concussion (36.1%).

Conclusions:

These findings reflect a higher prevalence of concus-

sion in high school football players than previously reported in the

literature. The ultimate concern associated with unreported concus-

sion is an athlete’s increased risk of cumulative or catastrophic effects

from recurrent injury. Future prevention initiatives should focus on

education to improve athlete awareness of the signs of concussion and

potential risks of unreported injury.

Key Words:

brain concussion, head injury, athletic injuries.

(

Clin J Sport Med

2004;14:13–17)

ports-related concussion is now recognized as a major pub-

lic health concern

and has become the focus of increasing

interest from clinicians and researchers in sports medicine.

The retirement of several high-profile professional athletes

due to recurrent cerebral concussion has created an increased

awareness of the dangers and potentially long-term sequelae

associated with concussion. The volume of athletes participat-

ing in organized sports at the high school level creates an even

greater concern about the potential effects of concussion in

young sports participants.

The Centers for Disease Control and Prevention esti-

mate that approximately 300,000 sports-related concussions

occur annually in the United States.

The high incidence of

cerebral concussion in contact sports is well documented, but

has been studied most extensively in organized football.

Con-

cussion incidence rates in high school football were estimated

to be 20%

in the 1980s, but more recent studies have reported

incident rates of 3–6%.

3,5–7

There is a general consensus

among sports medicine professionals, however, that the rate of

concussion in contact and collision sports is higher than the

incidence of recorded injuries.

The diagnosis of sports-related concussion is perhaps

the most elusive challenge facing sports medicine clinicians.

There is no biologic marker for the detection of concussion or

any diagnostic tests with perfect sensitivity and specificity.

The detection and diagnosis of concussion on the sports side-

line are complicated further by a player’s tendency to under-

report or mask symptoms in anticipation of a more rapid return

Received for publication March 2003; accepted August 2003.

From the Neuroscience Center, Waukesha Memorial Hospital (Dr. McCrea

and Mr. Leo), Waukesha, WI; Department of Neurology, Medical College

of Wisconsin (Drs. McCrea and Hammeke), Milwaukee, WI; Department

of Psychology, University of Wisconsin–Milwaukee (Mr. Olsen), Mil-

waukee, WI; and Departments of Exercise and Sport Science and Ortho-

pedics, University of North Carolina at Chapel Hill (Dr. Guskiewicz),

Chapel Hill, NC, USA.

Supported in part by the Waukesha Memorial Hospital Foundation, National

Academy of Neuropsychology, National Federation of State High School

Associations, NFL Charities, Green Bay Packer Foundation, Milwaukee

Bucks, Herbert H. Kohl Charities, Waukesha Service Club, Michael

Emme, and the Medical College of Wisconsin General Clinical Research

Center (M01 RR00058).

Reprints: Michael McCrea, PhD, Neuroscience Center, Waukesha Memorial

Hospital, 721 American Avenue, Suite 501, Waukesha, WI 53188 (e-mail:

michael.mccrea@phci.org).

Clin J Sport Med

• Volume 14, Number 1, January 2004

to play. The potential consequences of returning to contact or

collision sports while still symptomatic from an initial concus-

sion can be catastrophic,

8–10

which amplifies concern about

the risks associated with a player’s continued participation af-

ter an unreported concussion. Some authors have raised con-

cerns, however, that athletes themselves may not be suffi-

ciently aware of the signs, symptoms, and potential effects of

concussion.

11,12

Studies have reported on the link between a

lack of knowledge about the potential consequences from head

injury, failure to recognize concussion signs and symptoms,

and the likelihood that athletes continue sports participation

while experiencing head injury symptoms, especially among

football players.

The current study was designed to investigate the fre-

quency of unreported concussion among high school football

players to estimate more accurately the overall prevalence of

concussion in high school football players. In addition, reasons

that players did not report concussive events were surveyed to

formulate better recommendations for injury prevention strat-

egies. The main objectives of prevention initiatives are to in-

crease a player’s likelihood of reporting a concussion and to

reduce the risks of recurrent or catastrophic injury associated

with unreported head injury.

MATERIALS AND METHODS

A total of 1,532 varsity football players from 20 high

schools in the Milwaukee, Wisconsin, area were surveyed as

part of their enrollment in a larger study investigating the acute

effects and recovery following sports-related concussion. All

players completed a questionnaire on history and frequency of

previous concussion at the time of their initial enrollment in the

study.

Players were then administered a confidential question-

naire at the end of the football season (Appendix A). Specifi-

cally, players were asked to report on the number of concus-

sions sustained before the current football season. Players also

were asked whether they had sustained a concussion as part of

participation during the current football season. Players were

provided the following definition and description to determine

whether they had sustained a concussion: A concussion is a

blow to the head followed by a variety of symptoms that may

include any of the following: headache, dizziness, loss of bal-

ance, blurred vision, “seeing stars,” feeling in a fog or slowed

down, memory problems, poor concentration, nausea, or

throwing up. Getting “knocked out” or being unconscious does

not

always occur with a concussion.

14,15

The questionnaire and

definition of concussion were not based on any specific injury

classification system or concussion grading scale, but were in-

tended to provide respondents with a representative descrip-

tion of concussion signs and symptoms.

Players were asked whether they had reported their in-

jury and to whom it was reported. The following options were

provided, and players were informed that they should identify

all individuals to whom they reported their concussion: athletic

trainer, coach, parent, teammate, or other party. The reasons

why a player did not report a concussion also were surveyed.

Players could select one or more reasons for not reporting their

concussion from the following: didn’t think it was serious

enough, didn’t know it was a concussion, didn’t want to be

pulled out of the game or practice, didn’t want to let down

teammates, or other reason. A total of 92.3% (n = 1,532) of all

players enrolled (n = 1,659) during the preseason baseline test-

ing responded to the postseason questionnaire. This study was

approved by the institutional review board for the protection of

human research subjects at the host institutions of the investi-

gators.

Descriptive statistics were calculated to determine the

rates of reported and unreported concussion and frequency dis-

tributions for other variables. ? values were calculated from

cross-tabulations to determine respondent agreement on pre-

season and postseason surveys regarding reported concussion

history. ?

analyses were conducted to investigate factors as-

sociated with the likelihood of a player reporting a concussive

injury during the current season.

RESULTS

Overall, 30.4% and 29.9% of respondents reported a pre-

vious history of concussion on the preseason and postseason

survey, respectively. Preseason and postseason survey data on

concussion history were highly reliable (92.1% respondent

agreement; ? = 0.821,

< 0.0001). Of respondents who re-

ported a previous history of concussion, the frequency distri-

butions for the number of previous concussions reported on the

preseason and postseason surveys are illustrated in Figure 1.

A total of 229 players (15.3% of respondents) reported

that they sustained a concussion, as defined by the postseason

FIGURE 1. Reported history and frequency of previous concus-

sions on preseason and postseason survey.

Notes

: Preseason

survey n = 1,659; postseason survey n = 1,532 (92.3% re-

sponse rate). Figures for number of previous concussion are

based only on subjects who reported a history of concussion

(preseason n = 505; postseason n = 458). There was 92.1%

respondent agreement in reported history of concussion on

preseason and postseason surveys (? = 0.814;

< 0.0001).

McCrea et al

Clin J Sport Med

• Volume 14, Number 1, January 2004

2004 Lippincott Williams & Wilkins

survey, during the current football season. Of the respondents

who reported sustaining a concussion during the football

season, only 47.3% reported the event. Injured players

who reported their concussion most commonly did so to a cer-

tified athletic trainer providing clinical coverage to the varsity

football team at their school. Injuries were reported less fre-

quently to coaching staff, parents, teammates, or other parties.

The frequency distribution for injury reporting is provided in

Table 1.

The most common reason for a concussion not being

reported was that the injured player did not think it was serious

enough to warrant medical attention. A player’s motivation

not to be withheld from participation and a lack of knowledge

regarding the signs of concussion were common, but less

frequent, factors contributing to a player not reporting an

injury. The frequency distribution for reasons why concus-

sions were not reported is provided in Table 2. There was

no significant relationship between a player’s prior history

of concussion (?

= 0.10;

= 0.43) or number of previous

concussions (?

= 10.03;

= 0.19) and the likelihood of

reporting a concussive injury during the current football

season.

DISCUSSION

Concussion at all levels of competitive football is con-

sidered by sports medicine professionals and players alike as a

relatively common occurrence. More recent studies have sug-

gested a significant decline in the rate of reported concussions

relative to studies reported in the 1980s,

3,4,7

but most agree that

published studies likely underestimate the overall rate of con-

cussion for athletes participating in contact or collision sports.

Results from the current study examining reported and unre-

ported concussion reflect a higher prevalence of concussion

among high school football players than that reported in pro-

spective studies that focused on assessment of reported injuries

only.

5,16

Taking into consideration the frequency of unre-

ported concussions, the current study suggests that closer to

15% of high school football players sustain a concussion each

season.

Players who fail to report a probable concussion while

participating in contact or collision sports expose themselves

to a heightened risk for cumulative or more serious effects

associated with a second injury if they continue to participate

while still symptomatic following their initial concussion.

The ultimate concern in this regard is the potential for cata-

strophic events associated with sports-related concussion,

such as “second impact syndrome.”

8–10

Second impact

syndrome occurs when an athlete sustains a second concus-

sion while still symptomatic from an earlier head injury. A

rapid course of neurologic deterioration is observed, typically

without opportunity for medical intervention to reverse the

complications, culminating in death or severe disability.

Most instances of documented second impact syndrome

stem from either a player not reporting an initial concussion

or a reported injury being improperly assessed and managed.

An athlete’s awareness of signs of injury and willingness

to provide a valid symptom report are crucial to the sports

medicine professional’s ability to diagnose and manage sports

concussion.

Our results indicating that high school football players

often do not report a probable concussion because they do not

think it is sufficiently serious was unexpected based on histori-

cal stereotypes. It has long been thought that football players

were reluctant to report a concussion based solely on competi-

tive factors—their motivation not to be withheld from compe-

tition. The current survey results suggest, however, that lack of

knowledge related to the risks and potential consequences of

concussion play an equal or greater role in high school football

players not reporting a probable concussion. The most com-

mon reason for an injury not being reported was that the player

did not think the injury was serious enough to warrant medical

attention. More than one third of players who failed to report

their injury did not recognize that they had sustained a prob-

able concussion based on their symptoms. When provided

with a definition of concussion and a description of injury

signs and symptoms, these players more readily recognized

and admitted to sustaining a concussion over the course of the

football season.

TABLE 1. Concussion Reporting Data*

Concussion Reported to:

Percentage

of Subjects

Certified athletic trainer

76.7

Coach

38.8

Parent

35.9

Teammate

27.2

Other (eg, family physician, student)

11.7

*Categories are not mutually exclusive; subjects were asked to check all

that apply.

TABLE 2. Reasons Why Concussions not Reported*

Why Concussion not Reported

Percentage

of Subjects

Did not think it was serious enough

66.4

Did not want to leave the game

41.0

Did not know it was a concussion

36.1

Did not want to let down teammates

22.1

Other reasons

9.8

*Categories are not mutually exclusive; subjects were asked to check all

that apply.

Clin J Sport Med

• Volume 14, Number 1, January 2004

Unreported Concussion in High School Football Players

These findings indicate the need for educational initia-

tives to inform young athletes of the effects and potential con-

sequences of concussion, which likely would have implica-

tions for preventing negative outcomes associated with sports

concussion, including second impact syndrome.

8–10

Prepar-

ticipation meetings could be offered to educate athletes, par-

ents, coaches, and others affiliated with athletic programs on

the signs and symptoms of concussion and to dispel many of

the myths about head injury (eg, that one must be rendered

unconscious to have sustained a concussion). Multimedia (eg,

instructional videos, interactive classroom presentations,

Web-based programs) approaches also could be used to dis-

seminate information on concussion management. Ultimately

the efficacy of educational programs in reducing the rate of

recurrent concussion and negative clinical outcomes should be

evaluated in controlled studies.

These survey results indicate that certified athletic train-

ers are the professionals most frequently called on to evaluate

and manage concussion in high school football players. These

injuries rarely were reported directly to a team or family phy-

sician. Even parents were less likely than the certified athletic

trainer to learn of the player’s concussion. These data support

the need for a systematic plan for injury reporting and manage-

ment that incorporates trained sports medicine professionals.

Advances in the education and training of physicians, certified

athletic trainers, and other sports medicine professionals are

critical to improve the standard of care in concussion assess-

ment and management.

Our results are limited by many factors inherent to sur-

vey research. We assumed a valid response from players based

on their retrospective recount of concussive injuries during a

period of approximately 3 months before the survey adminis-

tration. The consistency in previous concussion history and

frequency demonstrated on preseason and postseason surveys

supports the reliability and accuracy of player self-reports.

Their recollection of why an injury was not reported also may

be altered from the actual experience of injury during a sport-

ing event. The definition of concussion implemented in this

study was meant to be descriptive to the athlete, while address-

ing the main signs and symptoms addressed by various sys-

tems for classifying severity of sports concussion.

14,17–19

Re-

cent definitions are more inclusive in terms of mechanisms that

potentially can cause concussion and the scope of signs and

symptoms.

It is unclear how our results may have been af-

fected if a different description and definition of concussion

were offered to respondents. Despite these limitations, our

findings raise significant concerns about the actual prevalence

of concussion in high school football players and the propen-

sity on the part of athletes not to report a probable concussion.

Obtaining prospective data on unreported injuries, whether

concussion or other forms of injury, is often difficult to accom-

plish. We intend to compare self-report survey results with

more objective injury surveillance data as part of other ongo-

ing sports concussion studies to determine better the gap be-

tween identified and unidentified concussion in competitive

sports.

SUMMARY

These findings support the suspicion by sports medicine

professionals that the prevalence of concussion in high school

football is higher than that documented in the literature. Play-

ers seem to be largely unaware of common signs and symp-

toms indicating concussion and the potential seriousness of

continued participation in contact or collision sports after an

initial concussion. Future prevention initiatives should focus

on education to increase athlete awareness of concussion and

its risks and promotion of open lines of injury report.

ACKNOWLEDGMENTS

The authors thank the certified athletic trainers who as-

sisted in coordination of data collection at each participating

institution. The authors also thank all the players and their

coaches for their participation in the study.

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Unreported Concussion in High School Football Players