Research in Sports Medicine 11:157-172, 2003

A Two-Year Prospective Study of Cerebral Concussion in American Football

Eric D. Zemper, Ph.D.

Exercise Research Associates, Ann Arbor MI USA

Department of Physical Medicine & Rehabilitation, University of Michigan

ABSTRACT

The objective of this study is to investigate rates of concussion and selected factors related to its occurrence in American football players. A prospective epidemiological study followed a national sample of high school and college players for two seasons. There were a total of 14,997 player-seasons, over 1 million athlete-exposures to the possibility of injury, and 595 concussions recorded. The concussion rate for high school players is 0.56 concussions per 1000 Athlete-Exposures, for college players 0.58 per 1000 Athlete-Exposures, and 0.57 overall. Concussion is the second (high school) or third (college) most frequent injury, is 9-10 times more likely to occur in games than in practices, and over half are the result of helmet to helmet contact. The risk of sustaining a concussion is six times greater for individuals with a history of concussion than for individuals with no history. Further commentary on these and other results is presented.

Key Words: Brain injuries, brain concussion, mild traumatic brain injury, athletic injuries, relative risk, football

 

INTRODUCTION

Cerebral concussion is a relatively frequent occurrence in high risk contact sports such as American football. Because the great majority of these injuries are mild in nature and do not involve the loss of consciousness, the general public, and even many in the medical community, are not fully aware of the frequency of this injury. While those in the sports medicine community are becoming more aware of the potential seriousness and long term consequences of this injury, except when there are a flurry of newspaper accounts of concussions suffered by high profile professional players, little attention is paid to concussions by athletes or the general public.

The American Academy of Neurology has defined a concussion as a traumatically induced alteration in mental status (e.g., confusion, amnesia) that may or may not involve loss of consciousness (AAN 1997). A more extensive definition of concussion was proposed by the Concussion in Sport Group, a committee formed at the first International Symposium on Concussion in Sport, which met in Vienna, Austria, in 2001. This group defined concussion as "a complex pathophysiological process affecting the brain, induced by traumatic biomechanical forces" (Aubry, Cantu, Dvorak et al. 2002). The definition then lists five clinical, pathophysiological, and biomechanical injury constructs that may be used in defining the nature of a concussive head injury, and also states that loss of consciousness may or may not be involved.

Both of these recent definitions have been developed in an attempt to be more inclusive of what have been recognized as milder concussion symptoms that were not included in the long-standing definition of cerebral concussion published over 35 years ago by the committee on head injury nomenclature of the Congress of Neurological Surgeons (CNS 1966).

As part of a general study of the epidemiology of football injuries, data were collected over two fall football seasons (1997-1998) from a large national sample of American high school and college football players. For the purpose of further investigating the risk of concussion and the factors surrounding the occurrence of this injury, specific items of information were included in the data collection process that made it possible to do detailed studies of head injuries in this population.

METHODS

American football injury data used for this study were collected by the Athletic Injury Monitoring System (AIMS) from a national sample of 56 high schools and 46 colleges for the 1997 season, and 36 high schools and 48 colleges during the 1998 season. The subjects in this study were all individuals playing football at these schools during the 1997 and 1998 seasons. AIMS is a national sports injury data collection system designed by this author and capable of doing injury surveillance on a variety of sports, and is operated by Exercise Research Associates (ExRA). It meets the major criteria for reliable studies of sports injury rates outlined in 1987 by the American Orthopaedic Society for Sports Medicine (Thompson, Halpern, Curl et al. 1987). AIMS data previously has been used for published reports on a number of issues in sports medicine, including general injury rates (Zemper 1989), concussion rates (Zemper and Pieter 1994; Zemper in press), prophylactic knee braces (Zemper 1990; Zemper 1996), and football helmets (Zemper 1994).

Both the high school and college samples for this study were distributed by four geographic regions, and the college sample also was distributed by size of program (National Collegiate Athletic Association [NCAA] and National Association of Intercollegiate Athletics [NAIA] divisions). Based on geographic region and size of program of NCAA and NAIA members sponsoring football during the period of this study, a X2 test of goodness-of-fit showed no significant difference between the sample distribution and the actual distribution (X2=4.701, a =0.05, df=11, CV=19.675). This indicates the college sample was representative of the entire country by region and size of program, and therefore the results presented here for the collegiate level can reasonably be projected to the country as a whole.

The nature of the high school sample precludes as rigorously representative a sampling as possible with the college sample. The study protocol required a medically trained person on site (specifically, a certified athletic trainer), and only a relatively small proportion (~15%) of the more than 13,000 high schools that sponsor football teams in this country have athletic trainers on staff (compared with essentially all colleges). Very few of the athletic trainers who are working at the high school level are in smaller schools. Under these conditions the most reasonable approach was to sample a large number of high schools (albeit a small proportion of the total) and keep the sample representative by geographic region. The high schools in this sample were statistically representative by geographic region (X2=1.570, a =0.05, df=3, CV=7.815) and, with over 7000 total player-seasons over the two seasons, the total high school sample was considered adequate for the purposes of this study.

Utilizing simple, easy-to-use forms, data on exposure to the possibility of injury in practices and games, and on any injury that kept a player out of normal participation for one day or more (including any head injury whether on not time loss was involved), were returned on a weekly basis throughout each season by certified athletic trainers at each participating school. As data arrived, it was logged in and screened for completeness and consistency before being entered into computer storage files. A common problem with surveillance systems of this sort is incomplete data submission from the field creating "gaps" in the data. To prevent this problem in this study, the author maintained frequent mail and telephone contact with the athletic trainers, obtaining corrections of any inconsistencies in the reported data and reminding them to submit missing data. Through this process of "preventive maintenance" the response rate for data submission was extremely high. For the college sample 99.3% of the weekly reports were submitted, and for the high school sample the response rate was 98.5% over the two seasons.

The data on exposures and on injuries were used to calculate injury rates based on the following equation:

((# injuries reported) ÷ (# exposures)) x 1000 = injury rate per 1000 Athlete-Exposures

(An Athlete-Exposure is one player participating in one game or one practice where he is exposed to the possibility of being injured.) The data collected for the 1997 and 1998 seasons included 14,997 player-seasons and 1,042,117 athlete-exposures in games and practices. The total injury rate for all types of injuries for the high school players was 4.93/1000 A-E and for college players it was 5.91/1000 A-E. Table 1 presents a summary of the number of player-seasons and athlete-exposures collected in this study.

This study used a definition of concussion (noted previously) and a grading system for severity of cerebral concussion developed by the American Academy of Neurology (AAN 1997). Grade 1 on this scale indicates transient confusion that resolves in less than 15 minutes (the "bell ringer"); Grade 2 indicates symptoms that last longer than 15 minutes, but there is still no loss of consciousness; and Grade 3 is used for any concussion involving loss of consciousness.

 

TABLE 1

Summary of Exposure and Injury Rates for a National Sample of High School and College Football Players, 1997-1998 Seasons

 

# Player- Seasons a

# Athlete- Exposures b

Total Injuries/ 1,000 A-E

Total # Concussions

Concussions/ 1,000 A-E

High School

   7350

   485,631

4.93

273

0.56

College

   7647

   556,486

5.91

322

0.58

Combined     HS + College

14,997

1,042,117

5.45

595

0.57

a A Player-Season is one player participating in one football season. The total number of individual players in this study will be less than this number, because many players were participating in both seasons.

b An Athlete-Exposure (A-E) is one player participating in one game or practice, where he is exposed to the possibility of being injured

 

In addition to the weekly exposure and individual injury forms, at the beginning of each season the athletic trainers completed a form indicating how many players had a history of cerebral concussion anytime during the previous five years. This information was based on the known medical history of each player while at the high school or college, and on detailed medical histories obtained for each player when they enter a collegiate program. To further explore factors involved in head injuries, during the first year of this study the athletic trainers also indicated who was primarily responsible for fitting football helmets and whether or not these individuals had received specific training on helmet fitting.

The AIMS injury surveillance project, from which the data used in this report were derived, received approval from the ExRA human subjects review committee as exempt research involving collection of existing publicly available data, documents or records, with the information recorded in such a manner that subjects cannot be identified directly or through identifiers linked to the subjects.

RESULTS

General. During the two seasons there were 595 reported concussions (273 HS and 322 college) (Table 1). Concussions comprised about 10% of the total reported injuries. Approximately 4.0% of the sample population incurred concussions during this study. With an estimated 1.08 million participants in organized football in this country, that projects a total of approximately 43,000 concussions occurring each year for football players in this country. This is considerably less than the estimate of 250,000 commonly seen in the literature based on a study by Gerberich et al. (1983), but it does agree with recent, more refined estimates (Powell and Barber-Foss 1999; Maroon, Lovell, Norwig et al. 2000).

The cerebral concussion rates at the high school and college levels were quite similar, with a rate of 0.56 concussions per 1000 Athlete-Exposures (A-E) for high school players and 0.58 per 1000 A-E for college players. The combined rate is 0.57 concussions per 1000 A-E. Looked at another way, this is equivalent to one concussion in every 1754 times a player participates in a game or practice. For a team of 100 players (generating 100 A-E in every daily practice and every game, assuming they all played in the game), this would be one concussion in every 17-18 days of activity. A less accurate and less useful "rate" still commonly seen in sports medicine literature is the number of injuries per 100 players. For concussions in this sample, there were 3.71 concussions per 100 high school players and 4.21 concussions per 100 college players. While this appears to indicate the rate for college players is about 15 percent higher, because college players typically have more exposures (practices and games) during a season, the actual rates for high school and college players are in reality quite similar. This is one illustration of how trying to make comparisons using injuries per 100 players as a rate can be misleading (Zemper 1993).

Injury Ranking. Because this study collected data on all types of injuries, it is possible to look at the occurrence of cerebral concussions in relation to other types of injuries. The head is the third most frequently injured body part at the high school level, exceeded only by the ankle and the knee (Table 2). At the college level, the head is the fourth most frequently injured body part, following the knee, ankle and shoulder in that order. With regard to type of injury, cerebral concussions are the fourth most frequent injury at both levels, after ligament sprains, muscle strains and contusions (Table 3). What is not evident in these raw data summaries is how cerebral concussions rank in relation to other specific body part/injury type combinations (for instance, not all knee injuries are ligament strains; they include injuries such as contusions and meniscus injuries as well). When analyzed in more detail, cerebral concussions prove to be the second most frequent injury at the high school level (ankle sprains being the most common), and the third most frequent injury at the college level, following ankle sprains and knee ligament sprains and tears (Table 4).

 

TABLE 2

Most Common Body Parts Injured for a National Sample of High School and College Football Players 1997-1998 Seasons

 

Body Part

Percent of Total Injuries

         Injury Rate/          1,000 A-E

High School

Ankle

14.36

0.71

 

Knee

13.07

0.64

 

Head

11.77

0.58

 

Shoulder

10.31

0.51

 

Fingers/Thumb

  6.43

0.32

 

Upper Leg

  4.47

0.22

College

Knee

16.54

0.98

 

Ankle

14.02

0.83

 

Shoulder

11.40

0.67

 

Head

  9.85

0.58

 

Upper Leg (Quadriceps m.)

  6.11

0.36

 

Hamstring

  5.20

0.31

Combined

Knee

15.08

0.82

HS + College

Ankle

14.16

0.77

 

Shoulder

10.94

0.60

 

Head

10.66

0.58

 

Upper Leg (Quadriceps m.)

  5.42

0.30

 

Lower Back

  3.92

0.21

 

TABLE 3

Most Common Injury Types for a National Sample of High School and College Football Players  1997-1998 Seasons

 

Injury Type

Percent of Total Injuries

      Injury Rate/          1,000 A-E

High School

Ligament Sprain

28.94

1.43

 

Muscle Strain

16.70

0.82

 

Contusion

16.08

0.79

 

Concussion

11.44

0.56

 

Fracture

  8.89

0.44

 

Dislocation

  2.42

0.12

College

Ligament Sprain

30.86

1.82

 

Muscle Strain

19.64

1.16

 

Contusion

12.22

0.72

 

Concussion

  9.79

0.58

 

Fracture

  5.17

0.31

 

Heat Exhaustion

  2.77

0.16

Combined

Ligament Sprain

30.05

1.64

HS + College

Muscle Strain

18.40

1.00

 

Contusion

13.85

0.76

 

Concussion

10.47

0.57

 

Fracture

  6.74

0.37

 

Dislocation

  2.35

0.13

 

TABLE 4

Most Common Injuries for a National Sample of High School and College Football Players          1997-1998 Seasons

 

Injury

Percent of Total Injuries

Injury Rate/       1,000 A-E

High School

Ankle Ligament Sprain

13.11

0.65

 

Concussion

11.44

0.56

 

Knee Ligament Sprain/Tear

  8.69

0.43

 

Lower Back Muscle Strain

  2.84

0.14

 

Upper Leg (Quadriceps m.) Strain

  2.46

0.12

 

Finger/Thumb Fracture

  2.38

0.12

College

Ankle Ligament Sprain

13.26

0.78

 

Knee Ligament Sprain/Tear

12.01

0.71

 

Concussion

  9.79

0.58

 

Hamstring Strain

  5.14

0.30

 

Upper Leg (Quadriceps m.) Strain

  3.31

0.20

 

Heat Exhaustion

  2.77

0.16

Combined

Ankle Ligament Sprain

13.19

0.72

HS + College

Knee Ligament Sprain/Tear

10.61

0.58

 

Concussion

10.47

0.57

 

Hamstring Strain

  3.78

0.21

 

Upper Leg (Quadriceps m.) Strain

  2.96

0.16

 

Lower Back Muscle Strain

  2.62

0.14

 

Injury Situation. A breakdown of the situations in which concussions occur is presented in Table 5. The most frequent situations are tackling and being tackled, followed by blocking and being blocked. At both the high school and college levels, impact with the playing surface caused about 4% of the concussions.

 

Table 5

Most Frequent Activity at Time of Concussion for a National Sample of High School and College Football Players, 1997-1998 Seasons

 

High School

College

Total

 

% of Total

 

% of Total

 

% of Total

 

Activity

Concussions

Ratea

Concussions

Rate

Concussions

Rate

Being Tackled

28.21

0.16

22.36

0.13

24.54

0.14

Tackling

21.97

0.12

25.16

0.15

23.70

0.14

Blocking

20.15

0.11

22.36

0.13

21.34

0.12

Being Blocked

15.38

0.09

18.32

0.11

16.97

0.10

Impact with         Playing Surface

  4.40

0.02

  4.35

0.03

  4.37

0.02

a Rate per 1,000 Athlete-Exposures

                   

Games vs Practice. The rate of concussions in practice for high school players was 0.29 per 1000 A-E, while in games it was 2.59 per 1000 A-E. For college players the concussion rate in practices was 0.35 per 1000 A-E, and in games it was 3.55 per 1000 A-E. Both high school and college players were 9-10 times more likely to sustain a cerebral concussion in a game than they were in practice.

Helmet Impact Injuries. The athletic trainers noted whether each injury was directly caused by impact from another player’s helmet (i.e., "no; yes; uncertain"). Combining the high school and college data, direct impact from another player’s helmet appears to be the causative mechanism of a minimum of 16.6% of all football injuries, and possibly as much as 26.0% of all football injuries. (This is estimated by using the percentage of injuries definitely attributed to helmet impact as the minimum value and adding the percentage of injuries where the athletic trainer indicated that it was uncertain whether or not a helmet was involved, to give a maximum estimate.) When only cerebral concussions are considered, impact from another helmet was the direct cause of 56.7% of all cerebral concussions in football, and possibly as much as 76.7% of all concussions in this sport.

Time-Loss. The average time-loss for each grade of concussion in this sample is presented in Table 6. Because the average number of days lost can be skewed to the high side by a few instances where players were held out for the rest of the season, more informative statistics in this case would be the median number of days lost per injury, and the mode (the most frequently occurring number of days lost.)

 

TABLE 6

Time-Loss by Grade of Cerebral Concussion

Grade a

N

Mean

Median

Mode

1

398

  4.3d

2d

1d

2

179

14.4d

7d

2d

3

 18

18.2d

8d

--b

a American Academy of Neurology classification                                                                                                            b Because of the small n, there were multiple modes.

 

Helmet Fitting. At the college level just over 60% of the individuals responsible for fitting helmets were equipment managers, of whom all but 14% had specific training in fitting helmets. About a quarter of the individuals were athletic trainers, all of whom had training. Just over 20% of the responsible individuals were coaches, and 60% of them did not have any training. All of the individuals at the college level who did not have training were in the smaller (Division II and Division III) schools. Nineteen percent of the individuals responsible for fitting helmets at the college level did not have any specific training.

At the high school level the situation was different. Because high schools usually do not have professional equipment managers, the coach is most often the one responsible for fitting helmets. Coaches comprised nearly 70% of the responsible individuals in this sample, and 18% of the coaches did not have any training in fitting helmets. Most of the rest of the responsible individuals were the athletic trainers, and nearly all of them had training. Overall, in this sample about 15% of the individuals responsible for fitting helmets at the high school level had no training. Given that most high schools do not have either equipment managers or athletic trainers, it can be estimated that at about one in five high schools the person responsible for fitting football helmets has no training to do so.

Relative Risk of a Second Concussion. A history of previous concussion for each player was provided by 174 of the 186 team-seasons in this study. From the information that 975 (6.4%) of the players in this sub-sample had a history of concussion, plus data from the individual injury forms indicating whether or not a concussion being reported occurred in a player with a previous concussion, it is possible to calculate relative risk (in this case, the ratio of the risk among those with a history of concussion to the risk among those with no history of concussion). As reported in detail elsewhere (Zemper in press), the relative risk at the high school level is 6.7 (95% CI: 5.1, 8.9), for the college level 5.3 (95% CI: 4.3, 6.6), and the combined relative risk is 5.8 (95% CI: 4.8, 6.8).

In this large national sample of high school and college football players over two seasons, the risk of sustaining a cerebral concussion during the season is nearly six times greater for individuals with a history of concussion during the previous five years than for those with no previous history of concussion. From a different perspective, approximately 1 in 35 individuals with no previous history will sustain a concussion during a given season, while approximately 1 in 6 with a previous history will sustain a new concussion.

As seen in Table 7, the distribution of concussions by grade is essentially the same between those with no history and those with a history of concussion. A history of previous concussion did not appear to impact the severity of a new concussion, according to these data. Since Grades 1 and 2 do not involve loss of consciousness, these data also show that over 95% of the concussions in this sample did not involve loss of consciousness. An analysis of concussions by position played showed there were no differences between those with a history and those with no previous history of concussion, with the exception of offensive tackles with a history having significantly fewer than expected concussions and quarterbacks with a history having more than expected.

 

TABLE 7

Grade of Cerebral Concussion by History of Concussion a

Grade b

No History

History

Total

1

268 (65.2%)

101 (62.7%)

369 (64.5%)

2

132 (32.1%)

  52 (32.3%)

184 (32.2%)

3

  11   (2.7%)

    8   (5.0%)

  19   (3.3%)

(History vs No History comparison: c 2=3.338, a =0.05, df=2, CV=5.991)

a This table utilizes data only from schools that provided adequate history information.                                         b American Academy of Neurology classification

 

Concussion Experience by Year in School. To further investigate the patterns of concussions in high school and college football players, the distribution of the total concussions reported by year in school was calculated (Table 8). In addition, the proportion of concussions reported within each year cohort that were sustained by individuals with a history of previous concussion also was calculated. From this table it can be seen that the pattern of the percentage of the total reported concussions is different for high school and college players, increasing each year throughout the high school years, but declining after the first year of college. The proportion of concussions reported that were sustained by those with a history of concussion showed a similar pattern at both the high school and collegiate levels of play. The proportion initially rises each year for both high school and college players, and then declines in the last two years at each level of play.

 

TABLE 8

Percent of Total Concussions and Proportion of Concussed Players With a History of Concussion     by Year in School

 

Year in School

 % of Total Concussions

Proportion who Have History (%)

High School

Yr 1

  6.5

17.6

 

Yr 2

10.3

25.9

 

Yr 3

14.4

23.7

 

Yr 4

14.6

19.5

College

Yr 1

15.8

24.1

 

Yr 2

15.4

29.6

 

Yr 3

10.8

42.1

 

Yr 4

  9.1

39.6

 

Yr 5

  3.2

35.3

 

DISCUSSION

Cerebral concussion is a common problem that in the past has received little attention from those in the general population or from athletes (Goldstein 1990; Kelly 1999). The data presented here indicate that concussion is the second or third most frequent injury in American football, and players with a history of concussion within the previous five years are nearly six times more likely to suffer a new concussion than those with no history of concussion.

McCrory et al. (2001) have suggested that increased risk of a second concussion might be an artifact related to length of time involved with a collision sport like American football, and therefore might simply reflect the level of exposure. Other factors that possibly could impact the distribution of concussions in the study population include: a) the number of participants at each age/grade level, there generally being more younger players in the freshman and sophomore years and a drop off in numbers through the junior and senior years at both the high school and collegiate levels; b) the size, weight and speed, and therefore impact forces, which tend to increase with age and the progression from high school to college; and c) the tendency for athletes in their junior and senior years of high school or college to be playing more time in games than younger players, and therefore getting more exposure to the possibility of injury, since injury risk is much higher during the high intensity activity of games than during practices.

If McCrory et al. are correct, we would expect to see an increasing number of concussions with age or year in school (and amount of time exposed in the sport) and an increasing proportion of the total concussions in those with a prior history. If the larger numbers of younger players have a major impact, we would expect to see more concussions for the earlier years in school and a steady decline in number of concussions in later years. If higher impact forces for the older players have a major influence, we would expect to see an increase in concussion rate at the college level. If game exposure has a major impact on the distribution of concussions, we would expect to see more concussions and a greater proportion of repeat concussions among the upperclassmen of both the high school and college levels.

The actual situation is likely a complex combination of all these possible factors, as indicated by the data collected by this project, which show no consistent pattern matching any single one of these projections. The number of concussions increases with age and year in school for the high school players, as predicted by the suggestion of McCrory et al. or if game exposure had an overriding influence (Table 8). However, at the collegiate level the numbers of concussions decrease dramatically with age and year in school, which is predicted if the larger number of players at the younger ages has more influence rather than game exposure. The proportion of concussions that occur in individuals with a history of concussion increases initially with age and year in school at both levels, but then declines at the oldest ages in both the high school and collegiate samples. This does not match the pattern predicted if the suggestion of McCrory et al. is correct or if game exposure were the primary factor. Higher impact forces for older players appears to be an equivocal factor, since the concussion rate is only marginally higher for the collegiate level.

Another factor often mentioned with regard to risk of concussion in American football is the possibility that a player’s style of play or risk-taking behavior may increase the risk of concussion, and it is those players that have the repeat concussions. If this were the case, and assuming the more aggressive, risk-taking player tends to gravitate toward playing aggressive positions such as linebacker or defensive back, we would expect to see more concussions in specific positions and a greater proportion of repeat concussions in those positions. As indicated earlier in the results (Results: Relative Risk of a Second Concussion), analysis of second concussions by player position did not show this pattern.

These data indicate that the risk of sustaining a concussion is 9-10 times higher while participating in a game than it is while participating in a practice session (Results: Game vs Practice). This is not surprising, since the rate for all injuries in games previously has been found to be at least eight times higher than in practices (Zemper 1989; Zemper 1993). While the total number of concussions in practices in a given season may be higher than in games, it should be remembered that there are 5-6 times as many practices as games in a given season. Therefore, the rate, or the risk, of concussions as with other injuries is actually much higher in game situations (Zemper 1989; Zemper 1993; Mueller, Zemper and Peters 1996). This most likely is due to a much higher intensity level that is sustained throughout a game as compared to most practices.

Beyond the question of concussion risk, several of the results presented here, when taken together, appear to imply the need for a more vigorous and sustained education program for athletes and coaches regarding the head and the helmet in the sport of American football. The fact that cerebral concussion is the second or third most frequent injury (Table 4) should by itself raise some warning flags, especially when considering research showing that measurable cognitive deficits in memory and information processing occur for up to five days for most individuals (Macciocchi, Barth, Alves et al. 1996), and for as long as thirty days following a closed head injury (Gronwall and Wrightson 1974, 1975), even when there is no loss of consciousness. It should be kept in mind that these high school and college players have to perform in the classroom as well as on the field (Collins, Grindell, Lovell et al. 1999).

In addition, as noted in the results presented here (Results: Helmet Impact Injuries), anywhere from one-half to three-quarters of all football concussions involve direct impact from another player’s helmet, which implies that the head is still being used as an initial contact point far too often. Given the nature of this sport, there undoubtedly are many instances where such contact is accidental or unavoidable. But when the helmet is the causative agent in three to four times the percentage of concussions as it is for injuries in general, this is a strong indication that players still tend to drop their head and use it as a battering ram, particularly in head-on tackling situations. (This also has implications for the risk of neck injuries.) This is supported by the observation from these data that tackling and being tackled are generally the most frequent mechanisms for concussion. Finally, the observation that at about one in five high schools the person responsible for fitting helmets has no training to do so (and nearly that proportion of the smaller colleges) has implications for ensuring the optimal protective capabilities of the helmet as well.

To a certain degree all of these problems may be inter-related, and could be addressed by a comprehensive education program aimed at players (and their parents at the high school level), coaches and medical personnel. It needs to be more coordinated and more comprehensive than the sporadic attempts of the past, and should emphasize the dangers of using the head as an initial contact point and the importance of not returning to play while concussion symptoms are still present. It also would be appropriate to encourage governing bodies (state and national high school associations, NCAA, NAIA, etc.) to put much more emphasis on enforcement by game officials of the existing rules prohibiting use of the head as an initial contact point.

CONCLUSION

Concussions occur more frequently in American football than many people seem to realize. The data presented here show concussions are the second or third most frequent injury in this sport, and the majority of these injuries are the result of head-to-head contact. Previously reported results from this study (Zemper in press) indicate a previous concussion makes a player nearly six times more likely to suffer a new concussion. Others have noted there appears to be evidence of a lethal "second impact syndrome" (Saunders and Harbaugh 1984; Cantu 1998) as well as considerable evidence of measurable cognitive deficits for up to several days after even mild head injury (Macciocchi, Barth, Alves et al. 1996; Gronwall and Wrightson 1974, 1975). The results from this study, combined with those from other studies regarding "second impact syndrome" and cognitive deficits, point to a conclusion that the common practice of sending a player back into action as soon as he can "see straight" needs to be re-evaluated by those responsible for making these decisions. The data presented here also suggest the need for a more aggressive educational campaign regarding concussion for players, parents, coaches, officials and medical personnel involved in this sport.

 

Acknowledgements

The injury surveillance project, from which the data used in this manuscript were drawn, was funded by Riddell Inc. The author also wishes to acknowledge and thank the many certified athletic trainers who provided data for this project.

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