Expert Commentary

Sports-related concussions and traumatic brain injuries: Research roundup

Literature review of recent research related to brain injuries in youth and professional sports.

The issue of concussions in sports has attracted considerable media coverage in recent years. Understandably, the early focus was on professional football, a game built around high-speed, full contact between heavy, powerful players, but the scope of reporting and research has expanded widely to include sports at every level.

A pioneer of reporting in this field was Alan Schwarz of the New York Times; his work highlighted the history of concussions and their consequences in the NFL. The league has responded by banning some high-risk hits, and also aggressively investigated a “bounty pools” scandal that involved a team paying bonuses to players who injured opponents. (Similar behavior has even turned up in a Pop Warner youth league.) Retired players continue to pursue legal action and raise awareness of the issue, particularly with cases of former players suffering from early-onset dementia that can result from repeated brain trauma. In January 2013, the National Institutes of Health concluded that the former NFL linebacker Junior Seau, who committed suicide in May 2012, had been suffering from a degenerative brain disease.

Ice hockey is another rough, physical sport that takes a high toll. NHL all-star player Sidney Crosby was out for the better part of a year, beginning in 2010, because of a severe concussion. The long-term consequences of such injuries can be dire: A post-mortem of NHL “enforcer” Derek Boogaard, who died in May 2011, determined that he suffered from chronic traumatic encephalopathy, a progressive degenerative disease directly linked to repeated brain injuries.

Even professional sports that aren’t designed around physical contact between players can result in concussions. During the National Basketball Association 2012 Finals, Oklahoma City star James Harden suffered one just before the beginning of the playoffs. In Major League Baseball, concussions are known to have helped end the careers of Mike Matheny (now the manager of the St. Louis Cardinals) and Corey Koskie; they also cost Minnesota Twins star Justin Morneau the better part of a season of play. The league instituted a disabled list for players with concussions in 2011 and continues to work on the issue.

Concussion risk starts at the youth level, in football and ice hockey as well as baseball, soccer, boxing, gymnastics, horseback riding, skiing and cycling — any sport with potential for hard contact. The best available evidence continues to raise questions about whether schools and teams are doing enough. Two 2014 studies in The American Journal of Sports Medicine suggest as much: One study, which was based on a survey of 1066 collegiate institutions, concludes that “although a large majority of respondents indicated that their school has a concussion management plan, improvement is needed.” Another paper about protective equipment at the high school level found that among 2081 players enrolled during the 2012-13 football seasons, some 206 (9%) sustained a total of 211 concussions. That study notes that, regardless of the type and brand of protective equipment, incidence of concussion remains the same — suggesting that it is the nature of on-field play that remains at issue. Still, because of specific concerns over youth football, Virginia Tech and Wake Forest have started a ratings system for helmets.

According to the Centers for Disease Control and Prevention, U.S. emergency departments annually treat an average of 173,285 sports- and recreation-related traumatic brain injuries among children and adolescents. Such emergency visits have increased 60% over the past decade; in 2009 alone, there were 248,418 such cases.

New research from Harvard, Dartmouth, Brown and Virginia Tech has called into question whether current diagnostic techniques are adequate. In addition, the long-term effects of head injury are only partially understood. The Boston University Center for Traumatic Encephalopathy, which received a $1 million donation from the NFL in 2010, continues to examine the brains of deceased athletes to research and compile case studies on the long-term effects of concussions; the center also conducts other inquiries and publishes academic studies in this evolving field.

Finally, a 2014 study published in the journal of Medicine & Science in Sports & Exercise provides new evidence that high school athletes may be returning to the field too early after suffering a concussion.

Below are further studies and articles that bring a research perspective to questions around concussions in sports:


“The Spectrum of Disease in Chronic Traumatic Encephalopathy”
McKee, Ann C, et al. Brain, November 2012, 135 (11).

Excerpts: “Chronic traumatic encephalopathy [CTE] is a progressive tauopathy that occurs as a consequence of repetitive mild traumatic brain injury. We analysed post-mortem brains obtained from a cohort of 85 subjects with histories of repetitive mild traumatic brain injury and found evidence of chronic traumatic encephalopathy in 68 subjects: all males, ranging in age from 17 to 98 years (mean 59.5 years), including 64 athletes, 21 military veterans (86% of whom were also athletes) and one individual who engaged in self-injurious head banging behaviour…. CTE is a unique neurodegenerative condition that is associated with repetitive mild traumatic brain injury. Although there are many issues that require more thorough investigation, such as how much head trauma is causative, what type, and how frequent, the age when players are most susceptible and whether some individuals are genetically more prone than others, this study clearly shows that for some athletes and war fighters, there may be severe and devastating long-term consequences of repetitive brain trauma that has traditionally been considered only mild.”


“Spectrum of Acute Clinical Characteristics of Diagnosed Concussions in College Athletes Wearing Instrumented Helmets”
Duhaime, Anne-Christine, et al. Journal of Neurosurgery, October 2012.

Excerpt: “Data were collected from 450 athletes with 486,594 recorded head impacts. Forty-eight separate concussions were diagnosed in 44 individual players. Mental clouding, headache, and dizziness were the most common presenting symptoms. Thirty-one diagnosed cases were associated with an identified impact event; in 17 cases no specific impact event was identified. Onset of symptoms was immediate in 24 players, delayed in 11, and unspecified in 13. In 8 cases the diagnosis was made immediately after a head impact, but in most cases the diagnosis was delayed (median 17 hours). One diagnosed concussion involved a 30-second loss of consciousness; all other players retained alertness. Most diagnoses were based on self-reported symptoms…. Approximately two-thirds of diagnosed concussions were associated with a specific contact event. Half of all players diagnosed with concussions had delayed or unclear timing of onset of symptoms. Most had no externally observed findings. Diagnosis was usually based on a range of self-reported symptoms after a variable delay. Accelerations clustered in the higher percentiles for all impact events, but encompassed a wide range. These data highlight the heterogeneity of criteria for concussion diagnosis, and in this sports context, its heavy reliance on self-reported symptoms. More specific and standardized definitions of clinical and objective correlates of a ‘concussion spectrum’ may be needed in future research efforts, as well as in the clinical diagnostic arena.”


“Incidence of Sports-Related Concussion among Youth Football Players Aged 8-12 Years”
Kontos, Anthony P. Journal of Pediatrics, 2013.

Abstract: “Participants included 468 male youth football players in western Pennsylvania during the 2011 youth football season. Incidence rates (IRs) and incidence density ratios (IDRs) of concussion were calculated for games and practices and for age groups. There was a total of 11 338 (8415 practice and 2923 game) athletic exposures (AEs) in the study period, during which 20 medically diagnosed concussions occurred. A majority of concussions were the result of head-to-head (45%) contact. The combined concussion IR for practices and games was 1.76 per 1000 AEs (95% CI 0.99-2.54). The concussion IR was 0.24 per 1000 AEs (95% CI 0.04-0.79) in practices and 6.16 per 1000 AEs (95% CI 3.76-9.54) in games. The IDR for concussions in games to practices was 25.91 (95% CI 6.01-111.70). The IDR of concussions for youth aged 11-12 years compared with youth aged 8-10 years was 2.72 (95% CI 0.66-4.78).  The overall IR for concussion in youth football players aged 8-12 years was comparable with that reported previously for high school and collegiate samples. However, participation in games was associated with an increase in risk of concussion compared with practices, which was higher than rates previously reported for high school and collegiate athletes. Younger players were slightly less likely to incur a concussion than were older players.”


“Epidemiology of Concussions among United States High School Athletes in 20 Sports”
Marar, M., et al. American Journal of Sports Medicine, 2012.

Excerpt: “During the study period, 1,936 concussions were reported during 7,780,064 athlete-exposures (AEs) for an overall injury rate of 2.5 per 10,000 AEs. The injury rate was higher in competition (6.4) than practice (1.1) … The majority of concussions resulted from participation in football (47.1%, n = 912), followed by girls’ soccer (8.2%, n = 159), boys’ wrestling (5.8%, n = 112), and girls’ basketball (5.5%, n = 107). Football had the highest concussion rate (6.4), followed by boys’ ice hockey (5.4) and boys’ lacrosse (4.0)…. In gender-comparable sports, girls had a higher concussion rate (1.7) than boys (1.0)…. The most common mechanisms of injury were player-player contact (70.3%) and player-playing surface contact (17.2%). In more than 40% of athletes in sports other than girls’ swimming and girls’ track, concussion symptoms resolved in 3 days or less. Athletes most commonly returned to play in 1 to 3 weeks (55.3%), with 22.8% returning in less than 1 week and 2.0% returning in less than 1 day…. Although interest in sports-related concussions is usually focused on full-contact sports like football and ice hockey, concussions occur across a wide variety of high school sports. Concussion rates vary by sport, gender, and type of exposure. An understanding of concussion rates, patterns of injury, and risk factors can drive targeted preventive measures and help reduce the risk for concussion among high school athletes in all sports.”


“Response to Acute Concussive Injury in Soccer Players: Is Gender a Modifying Factor?”
Zuckerman, S.L., et al. Journal of Neurosurgery Pediatrics, October 2012.

Abstract: “Several studies have suggested a gender difference in response to sports-related concussion (SRC). The Concussion in Sport group did not include gender as a modifying factor in SRC, concluding that the evidence at that point was equivocal. In the present study the authors endeavored to assess acute neurocognitive and symptom responses to an SRC in equivalent cohorts of male and female soccer players. The authors hypothesized that female athletes would experience greater levels of acute symptoms and neurocognitive impairment than males…. The results failed to replicate prior findings of gender specific baseline neurocognitive differences in verbal and visual memory. The findings also indicated no differential gender based acute response to concussion (symptoms or neurocognitive scores) among high school soccer players. The implications of these findings for the inclusion of gender as a modifying factor in this tightly matched cohort are addressed.”


“Management of the Athlete with Concussion”
Su, John K., etc. Permanente Journal, 2012.

Excerpt: “The approach to and management of the athlete with concussion can be a challenging endeavor to physicians who care for athletes who have suffered a head injury—this group includes family physicians, pediatricians, internists, emergency medicine physicians, primary sports medicine physicians, orthopedic surgeons, neurologists, and neurosurgeons. Sometimes questions regarding the need for neurologic, psychological, or radiographic imaging can make the decision for return to play unclear. New legislation will undoubtedly increase physician visits for these athletes to return to play. Thus, the goal of this article is to review the latest guidelines regarding concussion management to help all physicians who care for athletes do so appropriately.”


“Head Impact Exposure in Youth Football”
Daniel, Ray W., et al. Annals of Biomedical Engineering, February 2012.

Abstract: “The head impact exposure for athletes involved in football at the college and high school levels has been well documented; however, the head impact exposure of the youth population involved with football has yet to be investigated, despite its dramatically larger population. The objective of this study was to investigate the head impact exposure in youth football. Impacts were monitored using a custom 12 accelerometer array equipped inside the helmets of seven players aged 7 to 8 years old during each game and practice for an entire season. A total of 748 impacts were collected from the 7 participating players during the season, with an average of 107 impacts per player. Linear accelerations ranged from 10 to 100 g, and the rotational accelerations ranged from 52 to 7694 rad/s2. The majority of the high level impacts occurred during practices, with 29 of the 38 impacts above 40 g occurring in practices. Although less frequent, youth football can produce high head accelerations in the range of concussion causing impacts measured in adults. In order to minimize these most severe head impacts, youth football practices should be modified to eliminate high impact drills that do not replicate the game situations.”


“Sports-Related Head Injury”
American Association of Neurological Surgeons, Patient Information Report, December 2011.

Excerpt: “A traumatic brain injury (TBI) is defined as a blow or jolt to the head, or a penetrating head injury that disrupts the normal function of the brain. TBI can result when the head suddenly and violently hits an object, or when an object pierces the skull and enters brain tissue. Symptoms of a TBI can be mild, moderate or severe, depending on the extent of damage to the brain. Mild cases may result in a brief change in mental state or consciousness, while severe cases may result in extended periods of unconsciousness, coma or even death.”


“Functionally-Detected Cognitive Impairment in High School Football Players Without Clinically Diagnosed Concussion”
Talavage, T.M., et al. Journal of Neurotrama, 2011.

Findings: Overall, the data suggest “the presence of a previously unknown, but suspected … group of athletes exhibiting neurocognitive deficits that persist over time, but which does not present observable symptoms.” The study’s authors say the findings indicate current on-field tests for concussions may not be sufficient in determining full risks to the brain.”


Nonfatal Traumatic Brain Injuries Related to Sports and Recreation Activities Among Persons Aged ≤ 19 Years: United States, 2001-2009
Gilchrist, Julie, et al. CDC Morbidity and Mortality Weekly Report, 2011.

Excerpt: “From 2001 to 2009, the number of annual [Traumatic Brain Injury-related Emergency Department visits] increased significantly, from 153,375 to 248,418, with the highest rates among males aged 10-19 years. By increasing awareness of TBI risks from sports and recreation, employing proper technique and protective equipment, and quickly responding to injuries, the incidence, severity, and long-term negative health effects of TBIs among children and adolescents can be reduced.”


“Assessment and Management of Sport-Related Concussions in United States High Schools”
Meehan, William P., et al. American Journal of Sports Medicine, 2011.

Excerpt: “Concussions account for nearly 15% of all sport-related injuries in high school athletes. The timing of return to play after a sport-related concussion is similar regardless of whether the decision to return the athlete to play is made by a physician or an AT. When a medical doctor is involved, most concussions are assessed by primary care physicians as opposed to subspecialists. Computed tomography is obtained during the assessment of 1 of every 5 concussions occurring in high school athletes.”


“Clinical Report: Sport-Related Concussion in Children and Adolescents”
Halstead, Mark E., etc. American Academy of Pediatrics, 2010.

Excerpt: “Sport-related concussion is a ‘hot topic’ in the media and in medicine. It is a common injury that is likely underreported by pediatric and adolescent athletes. Football has the highest incidence of concussion, but girls have higher concussion rates than boys do in similar sports. A clear understanding of the definition, signs, and symptoms of concussion is necessary to recognize it and rule out more severe intracranial injury… This report serves as a basis for understanding the diagnosis and management of concussion in children and adolescent athletes.”


“Trends in Concussion Incidence in High School Sports: A Prospective 11-Year Study”
Lincoln, Andrew E., et al. American Journal of Sports Medicine, May 2011.

Abstract: “Data were prospectively gathered for 25 schools in a large public high school system. All schools used an electronic medical record-keeping program…. 2651 concussions were observed in 10,926, 892 athlete-exposures, with an incidence rate of 0.24 per 1000. Boys’ sports accounted for 53% of athlete-exposures and 75% of all concussions. Football accounted for more than half of all concussions, and it had the highest incidence rate (0.60). Girls’ soccer had the most concussions among the girls’ sports and the second-highest incidence rate of all 12 sports (0.35). Concussion rate increased 4.2-fold (95% confidence interval, 3.4-5.2) over the 11 years (15.5% annual increase). In similar boys’ and girls’ sports (baseball/softball, basketball, and soccer), girls had roughly twice the concussion risk of boys. Concussion rate increased over time in all 12 sports…. Although the collision sports of football and boys’ lacrosse had the highest number of concussions and football the highest concussion rate, concussion occurred in all other sports and was observed in girls’ sports at rates similar to or higher than those of boys’ sports. The increase over time in all sports may reflect actual increased occurrence or greater coding sensitivity with widely disseminated guidance on concussion detection and treatment.”


“Catastrophic Sports Injury Research Twenty-Ninth Annual Report Fall 1982-Spring 2011”
Mueller, Frederick O., et al. Department of Exercise and Sport Science, University of North Carolina, 2011.

Description: “The National Center for Catastrophic Sport Injury Research collects and disseminates death and permanent disability sports injury data that involve brain and/or spinal cord injuries. The research is funded by a grant from the National Collegiate Athletic Association, the American Football Coaches Association, and the National Federation of State High School Associations. This research has been conducted at the University of North Carolina at Chapel Hill since 1965. Each year three annual reports are compiled.”


“Hockey Concussion: Is It Child Abuse?”
Hemond, Chris. Canadian Medical Association Journal, 2012.

Excerpt: “If not a stampede, it appears there is at least a slow shuffle of Canadian youngsters out of contact hockey as a result of widespread publicity about the parade of National Hockey League (NHL) superstars onto injured reserve lists. Meanwhile, one critic says Hockey Canada’s failure to implement even more stringent anti-concussion measures constitutes nothing short of ‘child abuse.’”


“Effect of Bodychecking on Rate of Injuries Among Minor Hockey Players”
Cusimano, Michael D., et al. Open Medicine, 2011.

Excerpt: “Bodychecking is a leading cause of injury among minor hockey players. Its value has been the subject of heated debate since Hockey Canada introduced bodychecking for competitive players as young as 9 years in the 1998/1999 season…. In this study, the odds of injury increased with decreasing age of exposure to bodychecking. These findings add to the growing evidence that bodychecking holds greater risk than benefit for youth and support widespread calls to ban this practice.”


“Consensus Statement on Concussion in Sport”
McCrory, P., et al. Journal of Clinical Neuroscience, 2009.

Excerpt: “This document is developed for use by physicians, therapists, certified athletic trainers, health professionals, coaches and other people involved in the care of injured athletes, whether at the recreational, elite or professional level. While agreement exists pertaining to principal messages conveyed within this document, the authors acknowledge that the science of concussion is evolving and therefore management and return to play (RTP) decisions remain in the realm of clinical judgment on an individualized basis.”


Tags: sports, children, youth, safety, research roundup


About The Author