In the past decade, few issues at the intersection of medicine and sports have had as high a profile or have generated as much public interest as sports-related concussions. Historically most concussions were not considered serious, and athletes who sustained them might be said to have been “dinged” or had their “bell rung.” The injured player would “shake it off” and return to play. Recent years have seen an increasing awareness and understanding that all concussions involve some level of injury to the brain and that athletes suspected of having a concussion should be removed from play for further evaluation (Aubry et al., 2002; CDC, 2013a; Halstead et al., 2010; Harmon et al., 2013; McCrory et al., 2005, 2009, 2013a).
The acknowledgment of the seriousness of sports-related concussions has initiated a culture change, as evidenced by campaigns to educate athletes, coaches, physicians, and parents of young athletes about concussion recognition and management (e.g., CDC, 2013c; NCAA, 2013; NFHS, 2013; USA Football, 2013a; USA Hockey, 2013); rule changes designed to reduce the risk of head injury (e.g., Pop Warner Little Scholars, 2012, p. 44; USA Hockey, 2011, p. 58); and the enactment of legislation designed to protect young athletes suspected of having a concussion (NCSL, 2013). Despite such efforts, there are indications that the culture shift is not complete. For example, a 2012 survey of high school football players suggests that even when knowledgeable about the symptoms and dangers of concussions, a majority of players thought it was “okay” to play with a concussion and agreed they would “play through any injury to win a game” (Anderson et al., 2013). Some youth baseball rules pertaining to the use of a continuous batting order, in which all available players are in
the line-up, penalize teams if a player must leave the game for any reason, including injury (USSSA Baseball, 2013, p. 10, Rule 7.02.D.1[c]). There are also anecdotal reports of players attempting to subvert pre-season baseline neurocognitive tests (Pennington, 2013).
Despite the increased attention to and recent proliferation of research on sports-related concussion, confusion and controversy persist in many areas, from agreement on how to define a concussion and the effects of multiple concussions on the vulnerability of athletes to future injuries, to when it is safe for a player to return to sports and the effectiveness of protective devices and other interventions in reducing the incidence and severity of concussive injuries (Wilde et al., 2012). Parents worry about choosing sports that are safe for their children to play, about selecting the equipment that can best protect their children, and, if a child does receive a concussion, about when is it safe for him or her to return to play or when it might be time to quit a much-loved sport entirely.
It is against this background that the Institute of Medicine (IOM) and National Research Council (NRC) convened the Committee on Sports-Related Concussions in Youth to review the science and prepare a report on sports-related concussions in youth from elementary school through young adulthood, including military personnel and their dependents (see Box 1-1 for the statement of task). The 17-member committee included experts in the areas of basic neuroscience, neuropathology, clinical expertise with head trauma in pediatric populations, sports medicine, emergency medicine, cognitive and educational psychology, psychiatry, bioengineering with an emphasis in pediatric biomechanics, youth sports organization representatives, active duty military training, epidemiology, statistics or statistical analysis and evaluation, and health communication (Appendix B). The committee was charged with reviewing the available literature on concussions, within the context of developmental neurobiology, regarding the causes of concussions, their relationship to impacts to the head or body during sports, the effectiveness of protective devices and equipment in preventing or ameliorating concussions, screening for and diagnosis of concussions, their treatment and management, and their long-term consequences. Specific topics of interest included
- the subacute, acute, and chronic effects of single and repetitive concussive and non-concussive head impacts on the brain;
- risk factors for sports concussion, post-concussion syndrome, and chronic traumatic encephalopathy;
- the spectrum of cognitive, affective, and behavioral alterations that can occur during acute, subacute, and chronic posttraumatic phases;
- physical and biological triggers and thresholds for injury;
- the effectiveness of equipment and sports regulations for the prevention of injury;
- hospital- and non-hospital-based diagnostic tools; and
- the treatment of sports-related concussions.
An ad hoc committee will conduct a study and prepare a report on sports-related concussions in youth, from elementary school through young adulthood, including military personnel and their dependents. The committee will review the available literature on concussions, in the context of developmental neurobiology, in terms of their causes, relationship to hits to the head or body during sports, effectiveness of protective devices and equipment, screening and diagnosis, treatment and management, and long-term consequences. Specific topics of interest include
- the acute, subacute, and chronic effects of single and repetitive concussive and non-concussive head impacts on the brain;
- risk factors for sports concussion, post-concussive syndrome, and chronic traumatic encephalopathy;
- the spectrum of cognitive, affective, and behavioral alterations that can occur during acute, subacute, and chronic posttraumatic phases;
- physical and biological triggers and thresholds for injury;
- the effectiveness of equipment and sports regulations for prevention of injury;
- hospital- and non-hospital-based diagnostic tools; and
- treatments for sports concussion.
Based on currently available evidence, the report will include findings on all the above and provide recommendations to specific agencies and organizations (governmental and nongovernmental) on factors to consider when determining the concussive status of a player. The report will include a section focused on youth sport concussion in military dependents as well as concussion resulting from sports and physical training at Service academies and recruit training for military personnel between the ages of 18 and 21. Recommendations will be geared toward research funding agencies (NIH, CDC, AHRQ, MCHB, DoD), legislatures (Congress, state legislatures), state and school superintendents and athletic directors, athletic personnel (athletic directors, coaches, athletic trainers), parents, and equipment manufacturers. The report will also identify the need for further research to answer questions raised during the study process.
Terminology and Parameters of Study
Recognizing that concussion is a subgroup of mild traumatic brain injury (mTBI) (see Figure 1-1), the committee chose to use the term “concussion” throughout the report.
However, given the variable use of the terms “concussion” and “mild traumatic brain injury” in the literature, the committee decided to use whichever term was used by the source when referring to specific studies or articles. For a specific definition of concussion, the committee chose to follow the current international consensus definition (McCrory et al., 2013a). Not only does it capture and provide more detail on the common elements of concussion, but the definition was developed through a formal consensus process and has been subject to review and revision on a regular basis (Aubry et al., 2002; McCrory et al., 2005, 2009, 2013a), which has permitted it to evolve along with the science of concussion. It is the committee’s expectation that this definition will continue to evolve.
The current international consensus definition of concussion, as determined at the Fourth International Conference on Concussion in Sport (McCrory et al., 2013a), is
Concussion is a brain injury and is defined as a complex pathophysiological process affecting the brain, induced by biomechanical forces. Several common features that incorporate clinical, pathologic and biomechanical injury constructs that may be utilised in defining the nature of a concussive head injury include:
- Concussion may be caused either by a direct blow to the head, face, neck or elsewhere on the body with an “impulsive” force transmitted to the head.
- Concussion typically results in the rapid onset of short-lived impairment of neurologic function that resolves spontaneously. However, in some cases, symptoms and signs may evolve over a number of minutes to hours.
- Concussion may result in neuropathological changes, but the acute clinical symptoms largely reflect a functional disturbance rather than a structural injury and, as such, no abnormality is seen on standard structural neuroimaging studies.
- Concussion results in a graded set of clinical symptoms that may or may not involve loss of consciousness. Resolution of the clinical and cognitive symptoms typically follows a sequential course. However it is important to note that in some cases symptoms may be prolonged.
In approaching its charge to examine many facets of sports-related concussions in youth, the committee first identified the age range of young people upon which it would focus and what types of activities it would recognize as a being “sports related.” On the question of age range, the committee chose to focus on children and youth ages 5 to approximately 21 years (i.e., elementary school through college age). Five years is the approximate age of most children entering elementary school (kindergarten) in the United States (Mulligan et al., 2012). Around that age, children also are becoming more developmentally ready to begin participation in organized sports and recreational activities (Purcell et al., 2005). In selecting the upper boundary for the age range, the committee agreed that, despite the continuation of brain development into the mid-twenties (see Chapter 2), sufficient development occurs by age 21 to use that as a convenient cutoff. Although there is a significant body of literature on sports-related concussion among college athletes, there is little that uniquely captures post-college-age individuals (approximately ages 21 to 23 years) through age 26 years. This age group tends to be included in studies that capture older adults as well. For this reason the committee chose “college age” (approximately 21 years) as the upper age boundary.
On the question of which activities should be regarded as “sports related,” the committee recognized that sports can be competitive or recreational, including everything from football and cheerleading to mountain climbing and extreme sports, and it further recognized that concussions can result from other types of physical activity that are not traditionally considered sports, such as playground activities, physical education classes, and ropes and combatives courses during military training. Thus, the committee
took a broad view of sports, defining it for the purpose of this report as any sort of vigorous physical activity that does not involve motorized vehicles.
Information Gathering Process
The committee conducted an extensive review of the literature pertaining to sports-related concussions. The committee began with an English-language literature search of online databases, including Academic Search Premier, the Cochrane Database of Systematic Reviews, Embase, Google Scholar, Lexis Law Reviews Database, Medline, PsychINFO, PubMed, Science Direct, Scopus, Web of Science, and WorldCat/First Search. Additional literature and other resources were identified by committee members and project staff using traditional academic research methods and online searches. Attention was given to consensus and position statements issued by relevant experts and professional organizations.
The current evidence base (i.e., research and publications in peer reviewed journals) has notable limitations. As noted already, the poorly defined and inconsistent use of terminology (e.g., “concussion,” “mild traumatic brain injury”) often makes it difficult to determine the applicability of the literature specifically to concussion. In addition, there is relatively little literature devoted specifically to concussion, compared with the published research available on more severe traumatic brain injury (TBI), especially in the younger age groups (i.e., 5 to 12 years). There are few rigorous evaluations of interventions to reduce the incidence of concussion, there is limited analysis of outcomes associated with the implementation of “concussion” laws, and there are relatively few data on the psychometric properties of sideline screening tools.
The committee focused its review of the literature on research published in peer-reviewed scientific literature and consensus or position statements from groups of experts and professional organizations relevant to the diagnosis and management of sports-related concussion. The committee found considerable variation in the quality of the research studies it reviewed. However, given the current paucity of research in the field, the committee determined that even studies of limited strength could provide some useful information. The committee was careful to include appropriate qualifications when it cited such research. In addition, the committee made every effort to include the most current research. However, strong evidence was sometimes found in older studies, and as some of these studies had not been replicated in recent years, in some cases they were the only available sources of data. In some areas, large-scale studies have not been done, and so the committee looked for whatever data were available from smaller-scale studies. Ultimately, the committee included in this study what it judged to be the best empirical literature available.
Given the limitations of the published literature, the committee used a variety of sources to supplement its review of the literature. The committee met in person five times and held two public workshops to hear from invited experts in areas pertinent to sports-related concussions in youth. Speakers included experts in the diagnosis, management, and rehabilitation of concussed athletes, including their reintegration into academic and athletic settings; genetic and neurogenetic sources of increased risk; the development of biomarkers and imaging technologies for concussion diagnosis and evaluation; protective equipment safety standards and effectiveness; and the role of sports rules and training in the prevention of sports-related concussion. The committee also heard from active duty military experts specializing in concussion policy and care and a representative from service academies specializing in training programs; stakeholder representatives, including athletes, parents, coaches, and officials; and representatives from youth sports organizations, such as the National Collegiate Athletic Association, the National Federation of State High School Associations, and the Amateur Athletic Union. (See Appendix A for open session agendas and speaker lists.)
The committee’s work was further informed by the work of bodies such as the international Concussion in Sport Group (McCrory et al., 2013a), the American Academy of Neurology (Giza et al., 2013), the American Academy of Pediatrics (Halstead et al., 2010), and the American Medical Society for Sports Medicine (Harmon et al., 2013), as well as by previous IOM and NRC reports, including Is Soccer Bad for Children’s Heads?: Summary of the IOM Workshop on Neuropsychological Consequences of Head Impact in Youth Soccer (IOM, 2002); Cognitive Rehabilitation Therapy for Traumatic Brain Injury: Evaluating the Evidence (IOM, 2011); Systems Engineering to Improve Traumatic Brain Injury Care in the Military Health System Workshop Summary (NAE and IOM, 2009); Gulf War and Health: Volume 7: Long-Term Consequences of Traumatic Brain Injury (IOM, 2008); Early Childhood Development and Learning: New Knowledge for Policy (IOM and NRC, 2001); From Neurons to Neighborhoods: The Science of Early Childhood Development (IOM and NRC, 2000); and How People Learn: Brain, Mind, Experience, and School (NRC, 1999).
Variability in Defining Concussion
The lack of reliable biomarkers for concussions and the reliance on a subjective symptom-based definition, combined with variations in terminology (e.g., “concussion” versus “mild traumatic brain injury”) and in the
definition of those terms, as well as evolving descriptions of the severity of concussion (e.g., grading scales, simple versus complex) pose challenges not only for understanding the epidemiology of sports-related concussion but also for interpreting the information on concussions that is available in the lay and professional literature. Recognition of the need for common definitions and terminology has led to recent efforts to develop consensus definitions and common data elements for TBI research, including adult and pediatric concussion/mTBI research (Aubry et al., 2002; Hicks et al., 2013; McCrory et al., 2005, 2009, 2013a; Menon et al., 2010; NINDS, 2013; Thurmond et al., 2010). The Federal Interagency Traumatic Brain Injury Research (FITBIR) informatics system, developed by the Department of Defense and the National Institutes of Health, is a federal database designed to promote data sharing across the field of TBI research (NIH, 2013). The common data elements for TBI research that have been identified through an ongoing federal interagency initiative (Hicks et al., 2013; Thurmond et al., 2010) form the cornerstone of the FITBIR informatics system data dictionary (NIH, 2013). Participation in such collaborative research efforts may help to advance TBI research through the use of common definitions and standards.
A 2010 position statement issued by a working group of the interagency initiative to develop common data elements for TBI research defines TBI as “an alteration in brain function, or other evidence of brain pathology, caused by an external force” (Menon et al., 2010). This definition of TBI has been adopted by the National Institute of Neurological Disorders and Stroke, the National Institute on Disability and Rehabilitation Research, and other members of the International and Interagency Initiative toward Common Data Elements for Research on Traumatic Brain Injury and Psychological Health as well as by the Brain Injury Association of America (BIAA, 2011; Menon et al., 2010). The term “TBI” does not represent a single, uniform condition, but rather refers to a myriad of brain injuries of different types and severity that may result from varied causes. Even within traditional classifications of TBI as mild, moderate, or severe, there are different types of injury and different degrees of severity. This great variation helps to explain why there are no simple answers to the definition, diagnosis, or treatment and management of TBI.
Although some sources explicitly use the terms “mild traumatic brain injury” and “concussion” synonymously (CDC, 2009; DoD, 2012a), the committee has found it most useful to view concussion as a subset of mTBI (see Figure 1-1; Giza et al., 2013; Harmon et al., 2013; McCrory et al., 2013a,b). Even among concussions, one finds variation in the symptoms experienced by individuals as well as differences in the severity and duration of symptoms. Efforts to standardize a definition of concussion date back to the mid-1960s (Congress of Neurological Surgeons, 1966). More
recently, a number of professional groups, including the American Academy of Neurology; governmental bodies, such as the U.S. Centers for Disease Control and Prevention (CDC) and the Department of Defense; and a consensus group organized by international sporting bodies (Concussion in Sport Group) have advanced working definitions of concussion (CDC, 2012; DoD, 2012a; Giza et al., 2013; McCrory et al., 2013a). Although the specifics of the definitions differ, there are common elements. A concussion is understood to be a clinical syndrome involving a disturbance in brain function that is generally time-limited and results from biomechanical forces, such as a bump, blow, or jolt to the head or body (DoD, 2012a; Giza et al., 2013; Harmon et al., 2013; McCrory et al., 2013a,b). In addition, a concussion may, but usually does not, involve loss of consciousness and typically does not result in structural changes observable using standard imaging techniques, such as computed tomography or magnetic resonance imaging. These elements are captured in the consensus definition of concussion adopted by the committee (McCrory et al., 2013a).
The estimates of sports-related concussions provided by published epidemiologic data are most likely conservative, given that many concussions go unreported (Daneshvar et al., 2011; McCrea et al., 2004). Moreover, the lack of consensus on the definition of “concussion” and the reliance on athletes to self-report their symptoms, combined with various methodological differences, including varying study designs (retrospective versus prospective) and sources of data (emergency departments, athletic trainers, coaches, parents) and differences in what is being measured (concussions, mTBIs, all TBIs), have made estimating injury rates difficult, and the accuracy of much of the existing data is unknown (Daneshvar et al., 2011; McCrea et al., 2004). In the interest of accuracy, the following discussion uses the terms (e.g., TBI, mTBI, concussion) employed by the papers cited. The variations in terminology highlight one of the challenges for understanding the epidemiology of sports-related concussion.
One frequently cited paper estimated that as many as 1.6 million to 3.8 million sports- and recreation-related TBIs may occur annually in the United States, although the authors note that this number might be low because many such injuries may go unrecognized (Langlois et al., 2006). The figure is based on estimates generated from the unintentional injury supplement1 to the 1991 National Health Interview Survey (NHIS), which estimated that the annual number of sports- and recreation-related TBIs
1NHIS supplements are designed to capture data beyond those generated by the core questionnaire. Supplements may be used only once or repeated as needed (CDC, 2013d).
involving a loss of consciousness was approximately 300,000 across all age groups (Thurman et al., 1998). Citing studies suggesting that only 8 to 19.2 percent of sports-related concussions involve loss of consciousness (Collins et al., 2003; Schultz et al., 2004), Langlois and colleagues (2006) used these percentages to scale up the 300,000 TBIs involving loss of consciousness to 1.6 million to 3.8 million sports- and recreation-related TBIs annually.
A study using data from 15 National Collegiate Athletic Association (NCAA) sports found that between the 1988-1989 and 2003-2004 academic years, the overall reported concussion rate doubled, from 1.7 to 3.4 per 10,000 athletic exposures2 (AEs), with an average annual increase of 7.0 percent (Hootman et al., 2007). A study of high school athletes in a large public school system showed an increase in the overall rate of reported concussions from 1.2 to 4.9 per 10,000 AEs between the 1997-1998 and 2007-2008 academic years, with an average annual increase of 16.5 percent (Lincoln et al., 2011). There was a substantial increase in reported concussion rate beginning in 2005, the same year that more training staff were added at each of the high schools in the study (Lincoln et al., 2011). Similarly, the CDC has estimated that between 2001 and 2009 the number of children and adolescents age 19 years and younger in the United States who were treated in emergency departments (EDs) for concussions and other nonfatal, sports- and recreation-related TBIs increased from approximately 150,000 to 250,000 (Gilchrist et al., 2011).3 The rate of ED visits for such injuries increased 57 percent, from 190 to 298 per 100,000 population during that time period (Gilchrist et al., 2011). During the same time period, the number of ED visits for TBIs that required hospitalization varied, but did not show an increasing trend over time (Gilchrist et al., 2011).4 A num-
2Athletic exposures are the number of practices and competitions in which an individual actively participates (i.e., in which he or she is exposed to the possibility of athletic injury).
3The NEISS Coding Manual contains a specific diagnostic code for “concussion” while coding other closed head injuries (TBIs) (e.g., subdural hematoma) as “internal organ injury” with “head” coded as the body part affected (CPSC, 2013b). The CDC report discussed here includes both types of injury.
4Using data from the National Hospital Ambulatory Medical Care Survey, another study examined a 5-year sample (2002-2006) of ED visits for diagnosed concussion in children and adolescents age 19 years and younger (Meehan and Mannix, 2010). The study found that 30 percent of all the diagnosed concussions (approximately 43,200 annually) were sports-related. A higher percentage of concussions in adolescents (11 to 19 years) was attributed to sports than in children under 11 years of age (41 percent versus 8 percent), although percentages do not take rates of participation in sports activities into account. The inclusion criteria for this study were more restrictive than in the CDC report. Only patients with a diagnosis of concussion were included. Patients with other diagnoses, such as skull fractures or unspecified intracranial injury, were included only if they also were diagnosed with concussion. Patients diagnosed with an intracranial hemorrhage were automatically excluded.
ber of factors may have contributed to the increases in reported concussion rates, including increased awareness and recognition of such injuries.
Appropriate epidemiological surveillance can provide valuable data on the incidence, causes, and other information pertinent to the occurrence of sports-related concussions. Such data are important for informing the development of appropriate interventions to reduce the incidence of concussions in youth sports and enabling the assessment of the effectiveness of such interventions. Currently most of the reported epidemiologic data on sports-related concussions in youth come from three surveillance systems (see Table 1-1):
- National Electronic Injury Surveillance System—All Injury Program (NEISS-AIP)
- NCAA Injury Surveillance System (NCAA ISS)
- High School RIO™ (Reporting Information Online)
The CDC data that were previously reported come from the NEISSAIP, which captures data for individuals treated for injuries in emergency departments (CPSC, 2013c; Gilchrist et al., 2011; Hinton, 2012). NEISSAIP is the only ongoing surveillance system that captures sports injury data from nonacademic settings and for children younger than high school age. Operated by the U.S. Consumer Product Safety Commission, NEISS-AIP is an expansion of the National Electronic Injury Surveillance System (NEISS), which was originally launched in the early 1970s and captures data from a national probability sample of approximately 100 hospitals with emergency departments in the United States and its territories (CPSC, 2013a,b,c). NEISS data inform national estimates of the number of injuries associated with, although not necessarily caused by, specific consumer products. This distinction is important because a head injury might be attributed to “baseball” even though it occurred during a backyard “sword fight” with baseball bats. In 2000 NEISS-AIP was developed as a subset of NEISS to capture information on all injuries treated in the emergency departments, not only those related to products (CPSC, 2013a). Like NEISS, NEISS-AIP captures data on individuals’ age, sex, race, ethnicity, injury diagnosis, and affected body parts as well as the incident locale and product involved (if any), where injured person goes when released from the ED, and also a brief narrative description of how the injury occurred (CDC, 2013b; CPSC, 2013a; Hinton, 2012). Although NEISS-AIP includes data on race and ethnicity, an analysis of the NEISS data found that race and ethnicity were not
|Data System||Design||Population and Years Covered|
|NEISS-AIP (National Electronic Injury Surveillance System—All Injury Program)||
• Sub-sample (n=66) of a national probability sample of 100 hospitals with 24-hour emergency departments (EDs) in the United States and its territories
• Individuals treated for injuries in participating EDs
• 2001 to date
|NCAA ISS (NCAA Injury Surveillance System)||
• Sample of NCAA schools across the three divisions, number varies by year and sport, ranging from an average of 53.5 schools in 2004-2009 to an average of 26.5 in 2009-2013 across the sports reported in Table 1-2
• NCAA athletes
• 1982-1983 academic year to date (the number of sports covered has increased from only football to 25—men’s and women’s sports are counted separately)
|Source of Data||Strengths||Limitations|
• Medical record abstraction
• All age groups
• All sports and recreational activities
• Nationally representative ED data over time (years)
• Only injuries treated in EDs
• Injuries seen in EDs may be more severe
• Only captures primary diagnosis
• Variability in diagnosis of concussion
• Variable data on mechanism and circumstances of injury, including injuries involving sporting equipment in non-sports scenarios being categorized as sports-related
• Number of injuries only; cannot be used to calculate injury rate
• Reports by athletic trainers at participating programs
• Includes participation data; can be used to calculate injury rate
• Includes data on mechanism of and circumstances of injury (e.g., practice vs. competition, position, event)
• Provides data over time (years)
• Only college-age athletes
• Limited to 16 competitive sports
• Does not account for differences in playing time
• Cannot capture unreported injuries
• Has not always recorded non-time-loss injuries
|Data System||Design||Population and Years Covered|
|High School RIO™ (Reporting Information Online)||
• Sample of U.S. high schools that have athletic trainers, number varies by year and sport, ranging from 95 in 2005-2006 to 208 in 2012-2013
• High school athletes
• 2005-2006 academic year to date (the number of sports covered has increased from 9 to 20—boys’ and girls’ sports are counted separately)
One positive aspect of NEISS-AIP is that it provides nationally representative ED data over a long period of time. However, a major limitation of using NEISS-AIP to estimate the incidence of sports-related concussion is that it captures data only on individuals treated in EDs, whereas many concussions are treated by athletic trainers, physicians, and other qualified personnel in other venues, and many concussions are not reported at all (Gilchrist et al., 2011; Hinton, 2012). Not only will many sports-related concussions not be captured by NEISS-AIP, but individuals who seek care from EDs may be more severely injured than those who receive care from athletic trainers or personal physicians, which may skew the data. Furthermore, NEISS-AIP captures only the primary diagnosis and body part injured and does not capture cases in which concussion was a secondary diagnosis (Gilchrist et al., 2011). In addition, little is known about the consistency of the diagnoses made by the many physicians treating patients in the various sampled hospitals (Bazarian et al., 2006; Powell et al., 2008). Errors also may be introduced during the hospital-based NEISS-AIP coordinator’s identification and abstraction of pertinent medical records for inclusion
5From 1999 through 2007, an average of 26 percent of cases failed to include data for race and ethnicity.
6Racial and ethnic differences in rates of reported injury may reflect a number of factors. These include cultural and psychosocial factors, real or perceived experiences of discrimination in the health care system that can affect how and whether individuals seek care and the quality of the care that they receive, socioeconomic status, education, and access to care. Such differences, if they are found to exist, will suggest areas for future investigation.
|Source of Data||Strengths||Limitations|
• Reports by athletic trainers at participating programs
• Includes participation data; can be used to calculate injury rate
• Includes data on mechanism of and circumstances of injury (e.g., practice vs. competition, position, event)
• Provides data over time (years)
• Only high-school-age athletes
• Limited to competitive sports at participating high schools
• Does not account for differences in playing time
• Cannot capture unreported injuries
• Has not always recorded non-time-loss injuries
and coding in NEISS-AIP (CPSC, 2013a). Yet another limitation is the variable quality of the data on the mechanism of injury that are captured. As previously noted, an injury may be attributed to a product (e.g., baseball bat, ice skates) even when the injury occurred through some non-sports-related scenario, such as twirling around with a baseball bat or being hit in the head with an ice skate while cleaning out a closet. The narrative section of the report may include information about how the injury actually occurred—for example, during organized or informal athletic activity, during competition or practice, or in some non-sports-related accident—but the quality of the information in the narrative section also varies (Gilchrist et al., 2011; Hinton, 2012). Finally, NEISS-AIP collects information only on the number of injured individuals treated in emergency departments and not on the size of the populations among which the injuries occurred (Gilchrist et al., 2011; Knowles et al., 2010). Consequently, NEISS-AIP data cannot be used to estimate injury rates per 1,000 AEs or relative risks (e.g., for specific sports).
The NCAA ISS, begun in 1982, collects injury and exposure data from a representative sample of institutions across the NCAA’s three divisions in a variety of sports (Dick et al., 2007). In 2004, the NCAA injury surveillance program began using an online reporting system, and in 2009, the Datalys Center for Sports Injury Research and Prevention, Inc., assumed management of the program (Datalys Center, 2013b). The number of NCAA institutions participating in the NCSS ISS has varied over time and among sports. Prior to 2009, schools were recruited to report all applicable sports, although not all participating schools offered and hence reported on every sport. Since 2009, schools are recruited on a per sport basis, so
data may be reported for only one sport from a given school. From 2004 to 2009, an average of 53.5 schools across the 14 sports listed in Table 1-2 reported data for those sports—ranging from less than 20 schools for men’s and women’s ice hockey to approximately 90 schools for men’s and women’s basketball (Datalys Center, 2013b). From 2009 to 2013, the average number of schools reporting across the 14 sports dropped to 26.5—ranging from 10 for field hockey to 41 for women’s soccer (Datalys Center, 2013b).
Data are collected by athletic trainers on male and female participants in 25 sports from the first day of official pre-season practice through the final day of any postseason competition (personal communication with Datalys Center for Sports Injury Research and Prevention, Inc., September 23, 2013), although, as stated, not all schools report data for every sport. The athlete-related data captured include year in school, age, height, weight, and sex. Data on race and ethnicity are not collected. The NCAA ISS captures data on participation as well as on injury, and, in contrast to NEISS-AIP, it can be used to calculate injury rates for the sports it tracks.
|Lincoln et al. (1997-2008)||Gessel et al. (2005-2006)||Marar et al. (2008-2010)||Datalys Centera (2010-2012)|
|Ice Hockey (W)||—||—||—||—|
|Ice Hockey (M)||—||—||5.4||—|
aReported rates are based on preliminary data from NATA NATION reported by athletic trainers in participating high schools. Data collection began with 25 schools in 2010-2011 and currently has more than 100 participants in the 2013-2014 academic year.
bThe data from Hootman and colleagues (2007) represent 16 years (1988-2004), except in the case of women’s ice hockey for which data collection began in 2000.
Participation data are recorded in terms of athletic exposures, generally defined as one individual participating in one practice or competition in which he or she is exposed to the possibility of athletic injury, regardless of the time associated with that participation. As constructed, this definition cannot take into account the greater duration of exposure experienced by athletes with significantly more playing time compared with those who have less playing time. Because the NCAA ISS captures information only on injuries receiving medical attention by the team athletics trainers or physicians, it will not include data on concussions in athletes who did not report injury. Another weakness of the system in earlier years is that it recorded only time-loss injuries (i.e., those for which participation was restricted for 1 or more days beyond the day of injury) (Dick et al., 2007), which means it failed to capture data on any athletes with a concussion who return to full physical activity on the same day as the injury. This problem has since been rectified. From 2004 to 2009, data were captured on all concussion and dental injuries regardless of time lost, and since 2009, data are captured on all injuries regardless of time lost (Datalys Center, 2013b). The final limitation to the NCAA data is that, by definition, they are limited to
|Hootman et al. (1988-2004)||Gessel et al. (2005-2006)||Agel and Harvey (2000-2007)||Datalys Centerc (2004-2009)||Datalys Centerc (2009-2013)|
cData for the period 2004-2009 are from the NCAA Injury Surveillance System. The Datalys Center for Sports Injury Research and Prevention, Inc., assumed management of the NCAA injury surveillance program in 2009.
dRate calculated with fewer than 30 raw frequencies.
eAverage of participating teams over the time period.
SOURCES: Agel and Harvey, 2010; Datalys Center, 2013a,b; Gessel et al., 2007; Hootman et al., 2007; Lincoln et al., 2011; Marar et al., 2012.
college-age athletes and also do not include injuries for athletes participating in intramural, club, or recreational sports.
Modeled on the NCAA ISS and implemented in the 2005-2006 academic year, the High School RIO™, begun under the auspices of the Center for Injury Research and Policy at Nationwide Children’s Hospital in Columbus, Ohio, captures injury data annually for male and female athletes from a sample of high schools throughout the country that have athletic trainers (Center for Injury Research and Policy, 2013; Hinton, 2012; PIPER Program, 2013a). The number of schools that participate varies from year to year but has ranged from 95 in 2005-2006 to 208 in the 2012-2013 academic year (PIPER Program, 2013b). The number of sports represented has also increased over time from the 9 original sports to more than 20, although not every school reports data for all sports (Center for Injury Research and Policy, 2013; PIPER Program, 2013b). Data are collected on athletes’ year in school, age, sex, height, and weight, but not on their race or ethnicity. Athletic trainers report data weekly on athletic exposures and injuries, including information on the body site, diagnosis, severity, and injury event (e.g., mechanism of injury, activity, position or event, field or court location) (PIPER Program, 2013a). As with the NCAA ISS, the High School RIO captures participation data in terms of athletic exposures, permitting the calculation of injury rates for the sports it tracks, although it too does not take into account differences in playing time among athletes. Like the NCAA ISS, the High School RIO captures information only on concussions reported to or observed by the athletic trainers at the participating high schools, which means it may underestimate the occurrence of concussions. In addition, it too has not always captured data on non-time-loss injuries. Finally, by definition, the High School RIO captures data only on high-school-age youth and is further limited to those participating in the school-sponsored sports followed by the data system. As a result, it cannot provide complete epidemiologic data on sports-related concussion even within the high-school-age population.
The National Athletic Trainers’ Association National Athletic Treatment, Injury and Outcomes Network (NATA NATION) project is a 3-year effort sponsored by the NATA Research and Education Foundation and BioCrossroads to examine not only sports-related injuries but also treatments and patient-reported outcomes among high school athletes (Datalys Center, 2013a). Under the auspices of the Datalys Center for Sports Injury Research and Prevention, Inc., the project employs the same data collection technology and methodology used in the NCAA Injury Surveillance System. The NATA NATION project began in 2010-2011 with 25 schools participating and now has more than 100 participants in the 2013-2014 academic year. The number of schools reporting data on any one sport ranges from 25 to 51 for the 14 sports reported in Table 1-2 (Datalys Center, 2013a).
Coordinated efforts to collect sports-injury data for middle-school- and younger-aged youth are limited. A 2011-2012 Middle School RIO study, modeled on the High School RIO and NCAA ISS systems, collected injury data from a national sample of middle school and Pop Warner football players (Middle School RIO™, 2013). In addition, a 2-year study (2012 and 2013 seasons) of 10 youth football leagues of various sizes and demographics across six states is being conducted (USA Football, 2013b). The collection of data is under the auspices of the Datalys Center for Sports Injury Research and Prevention, Inc.
Factors Associated with Increased Incidence Rates of Reported Concussions
Despite the limitations of the surveillance data on sports- and recreation-related concussion, some patterns have emerged. Studies suggest that several factors may be associated with increased rates of reported concussion, such as competition level (youth, high school, college), sports setting (competition, practice), sex (female, male), and sport (e.g., football, soccer) (Covassin et al., 2003; Gessel et al., 2007; Hootman et al., 2007; Lincoln et al., 2011; Marar et al., 2012).
Competition level College athletes had higher overall rates of concussion than did high school students (4.3 versus 2.3 per 10,000 AEs) in nine sports during the 2005-2006 academic year, based on injury data from the NCAA ISS and the High School RIO surveillance systems (Table 1-2; Gessel et al., 2007). The relationship held true across all the sports, for female and male athletes, and for competition and practice, with the exception of practices in baseball, in which the college and high school rates were the same, and practices in softball, in which the high school rate was slightly higher than the college rate (Gessel et al., 2007). More recent data from the NCAA Injury Surveillance Program (2009-2013) and NATA NATION (2010-2012) indicate higher reported concussion rates among high school versus college athletes in football, men’s lacrosse, men’s soccer, and baseball (Table 1-2; Datalys Center, 2013a,b).
There are few equivalent data available to compare rates of reported concussion among younger athletes with those for high school and college athletes. USA Football (2013b) has commissioned a 2-year study of injury incidence, including concussion, among youth football players. During the 2012 season (the first year of the study), fewer than 4 percent of the 1,913 players ages 7 to 14 sustained a reported concussion from more than 60,000 athletic exposures, including practices and games (USA Football, 2013b), which suggests an overall approximate rate of 11.1 per 10,000 AEs. This is similar to the rate of 11.2 per 10,000 AEs reported for high
school students in the preliminary data from the NATA NATION project. A smaller study of youth football players ages 8 to 12 years found an overall reported concussion rate of 17.6 per 10,000 AEs during the 2011 season (Kontos et al., 2013). The study also found that players ages 11 to 12 were approximately 2.5 times more likely to sustain a reported concussion than players ages 8 to 10 years (25.3 versus 9.3 per 10,000 AEs) (Kontos et al., 2013).
Sports setting Several studies have examined the incidence of concussion during practice and competition. In general, reported concussion incidence is consistently higher in competition than in practice for both male and female athletes across all sports and age groups (Gessel et al., 2007; Hootman et al., 2007; Marar et al., 2012).7 In addition, the two studies of concussion incidence among youth football players also show a higher rate of concussion in competition than in practice (Kontos et al., 2013; USA Football, 2013b). The exception to this trend is in cheerleading, for which a study using High School RIO data for 2005-2006 showed a slightly higher absolute rate of reported concussion during practice than in competition (1.4 versus 1.2 per 10,000 AEs) (Marar et al., 2012).
Sex Studies that compared the rates of reported concussions for male and female athletes in three high school and college sports played by both sexes (soccer, basketball, and softball/baseball) found that females had a higher rate of reported concussions than did their male counterparts (Covassin et al., 2003; Datalys Center, 2013a,b; Dick, 2009; Gessel et al., 2007; Hootman et al., 2007; Lincoln et al., 2011; Marar et al., 2012). Although women’s lacrosse generally has demonstrated lower rates of reported concussion than has men’s lacrosse, the rules differ sufficiently to preclude direct comparison between the sexes (Datalys Center, 2013a; Hootman et al., 2007; Lincoln et al., 2011; Marar et al., 2012). Recent NCAA data, however, show equivalent or higher rates of reported concussion in women’s lacrosse than in men’s (Datalys Center, 2013b). Data on collegiate ice hockey also traditionally has shown a higher rate of reported concussion
7The data reported by Gessel and colleagues (2007) showed a concussion rate for practice that was equal or higher than the rate in competition for high school and college volleyball and high school softball during the 2005-2006 academic year. However, the total number of reported concussions in each group was low (6, 14, and 10, respectively). The 2 years of data reported by Marar and colleagues (2012) follow the trend of concussion rates being higher in competition than in practice for high school volleyball and softball. No additional data were available to evaluate the relative concussion rates for college volleyball.
for females than males (Agel and Harvey, 2010; Hootman et al., 2007),8 although the 2009-2013 NCAA data indicate a higher rate in men’s hockey than in women’s (8.2 versus 5.0 per 10,000 AEs) (Datalys Center, 2013b). (See Table 1-2.)
Sport The incidence of reported concussion appears to vary substantially by sport (see Table 1-2). For male athletes in the United States, football, ice hockey, lacrosse, wrestling, and soccer consistently are associated with the highest rates of reported concussions at the high school and college levels (Datalys Center 2013a,b; Gessel et al., 2007; Hootman et al., 2007; Lincoln et al., 2011; Marar et al., 2012). For female athletes, the high school and college sports associated with the highest rates of reported concussions are soccer, lacrosse, and basketball (Datalys Center, 2013a,b; Gessel et al., 2007; Hootman et al., 2007; Lincoln et al., 2011; Marar et al., 2012).9 In addition, women’s ice hockey has one of the highest rates of reported concussions at the college level (Agel and Harvey, 2010; Datalys Center, 2013b; Hootman et al., 2007), but no data are reported on the incidence of reported concussion for female athletes at the high school level.
There are very few studies that have examined sports-related concussions in youth outside of the high school and college settings and very few data on the incidence of reported concussions in different sports for youth younger than high school age (approximately age 14). The ED data captured in the NEISS-AIP database and reported by the CDC (see Table 1-3) and others provide some indication of the distribution by age of sports- and recreation-related activities and that have resulted in an ED visit for concussions or other nonfatal TBIs (Bakhos et al., 2010; Gilchrist et al., 2011), but the absence of participation data (the equivalent of the AEs captured by the NCAA ISS and High School RIO databases) precludes the calculation of injury rates. This is a problem because an activity such as bicycling, the activity most commonly associated with ED visits for nonfatal TBIs among girls ages 10 to 14 years, has a much different participation rate than, for example, horseback riding, which is the fourth most commonly associated activity for the same group (see Table 1-3). Assuming the participation rate for bicycling is much higher than that for horseback riding, the injury rate for bicycling would be lower than for horseback riding even though there were a greater number of injuries. As previously discussed, another
8Although Hootman and colleagues (2007) reported rates based on 16 years of NCAA ISS data for men’s ice hockey and 4 years of data for women’s ice hockey, for which data collection only began in the 2000-2001 academic year, Agel and Harvey (2010) used the same 7 years (2000-2007) of data for men’s and women’s ice hockey.
9The rate of reported concussion for field hockey from the NCAA data for 2009-2013 is uncharacteristically high (14.5 per 10,000 AEs), but was calculated from less than 30 raw observations and may not be reliable (Datalys Center, 2013b).
|Rank||Male Age Group (years)||Female Age Group (years)|
|All-terrain vehicle ridingb
aPercent of emergency department visits for nonfatal TBI by age and sex.
bAlthough the committee specifically excluded use of motorized vehicles from its definition of “sport,” the information is included here for the sake of completeness.
cIncludes cheerleading and dance.
SOURCE: Gilchrist et al., 2011.
disadvantage of the NEISS-AIP data is that it is limited to individuals who were treated in EDs, thereby not capturing youth with concussions and other nonfatal TBIs who received medical care in other venues, or who were never treated at all. The data may also represent more severe injuries than those treated in non-emergency settings.
So-called extreme sports are rapidly gaining in popularity, especially in the younger population. Examples of extreme sports include competitive skateboarding, mountain biking, and snowboarding jumps and tricks (e.g., half-pipes and terrain parks). Between 1998 and 2008, participation in skateboarding increased by 49 percent and participation in snowboarding increased by 51 percent; mountain biking, the second most popular extreme sport, also saw an increase in participation (Extreme Sport, 2008). Because extreme sports by definition involve a high level of inherent danger, either because of the environment in which they are played or as a result of the sport, they would seem to place participants at high risk for injury, including concussion. However, there are limited epidemiologic data on rates and types of injuries experienced by those participating in extreme sports. A prospective survey of 249 downhill mountain bike riders showed an overall injury rate of 16.8 injuries per 1,000 hours of exposure (Becker et al., 2013). The rate of all reported injuries for expert riders was significantly higher than was the rate of reported injuries for professional riders (17.9 versus 13.4 injuries per 1,000 hours of exposure), and the injury rate reported during competition was significantly higher than the rate for practice (20 versus 13 injuries per 1,000 hours of exposure). Extremities (lower leg and forearm) are the areas of the body most often reported injured. The rate of reported concussions was not provided. Another study reported that serious injuries to the head and neck are more likely to occur when a rider falls over the handlebars than when he or she falls off to the side, which implies that women are at higher risk than men for head and neck injuries because they generally weigh less and are more likely to fall over the handlebars (Kronisch et al., 1996). There is no discussion specifically of concussions, however.
Kyle and colleagues (2002) used NEISS-AIP ED injury data and participation data from the National Sporting Goods Association annual survey to calculate the rate of injuries seen in EDs for several sports. The rate of skateboard injuries seen in the ED (8.9 per 1,000 participants) was lower than that for snowboarding and bicycling (11.2 and 11.5 per 1,000 participants) and much lower than that for football and basketball (20.7 and 21.2 per 1,000 participants).
Military Personnel and Dependents
The committee was specifically asked to examine sports-related concussions among military dependents as well as concussions in military personnel ages 18 to 21 resulting from sports and physical training at military service academies and during recruit training. There are limited data available pertaining to this type of injury among the populations specified. With respect to the dependents of military personnel, there is no evidence about whether the risks for concussion are different for these youth than for youth in general, although there is no reason to think that they would be (Goldman, 2013; Tsao, 2013).
Among the U.S. military personnel worldwide (including the continental United States), approximately 26,000 concussions or mTBIs were diagnosed in 2012, representing about 85 percent of all TBIs in that population (DVBIC, 2013). Although TBI has become the signature injury of the wars in Iraq and Afghanistan, more than 80 percent of TBIs in the military do not occur in the deployed setting (DVBIC, 2013). These TBIs most commonly occur from motor vehicle crashes (privately owned and military vehicles), falls, sports and recreation activities, and military training (DVBIC, 2013).
Service academy students and the majority of military recruits fall within the age range specified by the committee. In fiscal year 2010, approximately 85 percent of active military recruits were between 18 and 24 years of age (DoD, 2012b). Although there is no reason to suspect that military personnel ages 18 to 21 who play intramural or service academy sports have different concussion risks than nonmilitary athletes of the same age participating in the same activities do, military service academies, such as West Point, require physical training activities, such as combatives and ropes courses, and offer other activities, such as boxing, that are not generally available at other collegiate institutions and that pose a high risk of concussion (Kelly, 2013; Wolfe, 2013). In an effort to reduce the number of concussions among cadets, West Point has substituted flag football for intramural football and eliminated intramural rugby altogether (Wolfe, 2013). Outside of the academies, there are anecdotal reports that many military personnel sustain concussions during hand-to-hand (combatives) courses during basic training (Sapien and Zwerdling, 2012), but data on the occurrence of concussions during such training have not been published in the peer-reviewed literature.
Overview of Outcomes and Reintegration
Eighty to 90 percent of individuals who sustain sports-related concussions fully recover within 2 weeks following injury (Covassin et al., 2010;
Eisenberg et al., 2013; Field et al., 2003; Makdissi et al., 2013; McClincy et al., 2006; McCrea et al., 2009, 2013), although high school athletes (14 to 18 years of age) seem to recover more slowly than do college-age athletes and those 11 to 13 years of age (Covassin et al., 2010; Eisenberg et al., 2013; Field et al., 2003). The other 10 to 20 percent have more protracted recovery periods, lasting weeks, months, or longer, as discussed in Chapter 4. Consensus has emerged that individuals suspected of having sustained a concussion should be immediately removed from the activity in which they are engaged and should not return to physical activity until they have been cleared by a health care provider knowledgeable about concussion diagnosis and management (Giza et al., 2013; Halstead et al., 2010; Harmon et al., 2013; McCrory et al., 2013a).
Athletes who return to play before their concussions have fully resolved may place themselves at an increased risk for prolonged recovery (Eisenberg et al., 2013) or more serious consequences if they sustain a second head injury (Cantu, 1998; Cantu and Voy, 1995; Collins et al., 2002; McCrory and Berkovic, 1998; Saunders and Harbaugh, 1984). Although very rare, the potential for catastrophic head injuries, including what has sometimes been called “second impact syndrome,” is the primary concern. While catastrophic head injury is uncommon, it may occur more frequently in younger athletes between the ages of 12 to 18 years (Boden et al., 2007, 2013; Cantu, 1998; Cantu and Voy, 1995; McCrory and Berkovic, 1998; Saunders and Harbaugh, 1984; Thomas et al., 2011). Due to development of the brain, adolescence has been suggested to be a time of increased risk of adverse consequences following concussion (Field et al., 2003).
Among youth, the primary focus of reintegration after a concussion often is a return to school, although reintegration also can encompass a return to work or, for members of the armed services, a return to duty. Because concussion symptoms may resolve before full cognitive recovery, students who are recovering from a concussion may require short-term accommodations upon returning to school. As discussed in Chapter 3, a number of states have developed plans or recommended resources for helping students return to academic activity.
Consensus guidelines for the return of athletes to athletic activity recommend a graded return-to-play protocol. Once an individual is symptom-free, the individual moves through a series of increasingly rigorous sport-specific activities, progression through which is governed in part by recurrence of symptoms (Halstead et al., 2010; McCrory et al., 2013a).
From the committee’s research, the public testimony it heard, and its collective expertise, the role of “culture” in the recognition and management of concussions in young athletes became apparent. Culture is created by the sum of beliefs and behaviors within a group. It is clear that currently the seriousness of the threat to the health of an athlete suffering a concus-
sion is too often not fully appreciated by athletes, their teammates, and, in some cases, coaches and parents (see, e.g., Anderson et al., 2013; Coyne, 2013; Echlin, 2012; Kroshus et al., 2013; McCrea et al., 2004; Register-Mihalik, et al., 2013a,b; Torres et al., 2013; Wolverton, 2013). In addition, athletes profess that the game and the team are more important than their individual health and often believe that by admitting to having symptoms of a concussion, they will be “letting down” their teammates, coaches, schools, and even parents (Anderson et al., 2013; Kroshus et al., 2013). A culture that encourages “playing through” a potentially concussive injury or returning to play too soon following a concussion can endanger the physical and cognitive well-being of the young athlete. Perhaps because concussions are “invisible” they are easier to ignore than torn ligaments or broken bones are. But each of these types of injury requires the athlete to be removed from play, cared for appropriately in both the acute stage and during the healing process, and judiciously returned to play only when he or she is demonstrably recovered. Increased knowledge about concussions in the absence of changes in attitudes may not be enough to modify reporting behavior among athletes (Anderson et al., 2013; Coyne, 2013; Kroshus et al., 2013; Register-Mihalik et al., 2013a,b; Torres et al., 2013). If the youth sports community can adopt the belief that concussions are serious injuries and institute behaviors and adopt attitudes that emphasize care for players with concussions until they are fully recovered, then the “culture” in which young athletes perform and compete will become much safer.
Similarly, military recruits are immersed in military values and culture, including devotion to duty, commitment, and service before self, and the idea that “there is no greater bond than the one they share with the people ‘to their left and their right’” (Halvorson, 2010), which may make them reluctant to self-report symptoms of concussion. The military has acknowledged the need for a culture change, as reflected in such efforts as teaming up with the National Football League to increase awareness about TBI and to effect a culture change in which military personnel and athletes are willing to seek help (and not be stigmatized) if they experience concussive symptoms (AP, 2012; Vergun, 2012).
The Policy Environment
In light of the potential for returning to play too soon having catastrophic results, lawmakers in the United States have passed legislation designed to address the need for concussion education for young athletes and their parents, particularly at the high school level, along with procedures to protect athletes from returning to play before it is deemed appropriate by health care providers. As of October 2013, 49 states and the District of Columbia had enacted concussion laws of some sort; legislation was intro-
duced in Mississippi, but it did not pass (NCSL, 2013; Network for Public Health Law, 2013; Sun, 2013). In May 2009, Washington became the first state to enact legislation designed to protect student athletes suspected of having sustained a concussion. Named after Zackery Lystedt, a 13-yearold football player who was permanently disabled when he returned to a game after having sustained a concussion, Washington’s law specifies several principles that have come to be viewed as the three tenets of model concussion legislation:
(1) education of coaches, parents, and athletes about the nature and risk of concussions in sports and a requirement that parents sign a form acknowledging receipt of the information;
(2) immediate removal from play of any youth athlete suspected of having sustained a concussion or head injury; and
(3) a requirement that an athlete who has been removed from play be evaluated by and receive written clearance from a health care professional trained in the evaluation and management of concussion before returning to play.
Although legislation in most of the states that have concussion laws includes some version of the three tenets in the Washington law, there is significant variation among states regarding specific requirements (NCSL, 2013; Network for Public Health Law, 2013).
Since 2009, there have been several federal legislative efforts directed at various aspects of sports-related concussions in youth. Legislation introduced in the House of Representatives—the Concussion Treatment and Care Tools (ConTACT) Act of 2009, later renamed the ConTACT Act of 2010 (H.R. 1347)—called on the Secretary of Health and Human Services to establish guidelines for “the prevention, identification, treatment, and management of concussions” in children 5 to 18 years of age, including return-to-play standards (H.R. 1347). In addition, the bill called for funding for states to collect data on the incidence and prevalence of sports-related concussion among school-aged children, to adopt and implement the aforementioned guidelines, and to implement pre-season baseline and post-injury testing for school-aged children (H.R. 1347). The bill eventually passed the House and was referred to the Senate (S. 2840), where it stalled in committee.
The Protecting Student Athletes from Concussions Act, originally introduced in the House in 2010 (H.R. 6172) and reintroduced in 2011 (H.R. 469), was directed toward state and local educational agencies and was, in part, designed to bring some uniformity to the proliferation of state “Lystedt laws.” The bill, which never moved out of committee, would have required as a condition of federal funding the development and implemen-
tation of a concussion safety and management plan that would include a concussion education component for students, parents, and school personnel; supports for students during recovery from concussion; and best practices to ensure uniformity in safety standards treatment, and management (H.R. 6172). Other elements of the bill called on school personnel to remove any student suspected of having sustained a concussion from the activity in which it occurred and to prohibit participation in athletic activities until the student was cleared by a health care provider, including recognition that the provider might specify a gradual, progressive return to cognitive and physical activity.
The Children’s Sports Athletic Equipment Act, jointly introduced in the House and Senate in 2011 (H.R. 1127; S. 601), was directed to the Consumer Product Safety Commission (CPSC) and addressed issues pertaining to the development of and compliance with standards for “youth football helmets, reconditioned helmets, and new helmet concussion resistance.” The 2011 bills died in committee, but similar legislation, the Youth Sports Concussion Act of 2013, was introduced in the House and Senate in May 2013 (H.R. 2118; S. 1014). The current legislation, which is in committee, is directed to the CPSC and addresses safety standards for protective equipment to reduce the risk of sports-related injury, to improve the safety of reconditioned protective equipment, and to modify warning labels on protective equipment. The legislation also addresses the issue of false or misleading claims in the marketing of protective equipment.
In February 2013, a resolution was introduced in the House (H.R. 72) supporting the goals and ideals of the Secondary School Student Athletes’ Bill of Rights (YSSA, 2013), which highlights the importance of proper safety measures and trained personnel, timely medical assessments, and appropriate environmental conditions in ensuring the health and well-being of secondary school student athletes.
State legislative efforts are addressed in more detail in Chapter 6.
Chapter 2 gives an overview of normal brain development, which provides the basis for understanding the pathophysiology and natural history of concussion. In addition the chapter discusses the mechanics of concussive injury, physical and biological thresholds for injury, and physical and behavioral risk and protective factors. Chapter 3 reviews considerations pertaining to the recognition, diagnosis, and acute management of concussions, including the reintegration of concussed individuals into academic and athletic activities. Chapter 4 discusses the treatment and management of individuals with concussion symptoms that persist beyond the typical 1- to 2-week recovery period. The chapter also includes a discussion of
special considerations that arise in the provision of concussion care, such as geographic variation in access to specialized care. Chapter 5 examines the issues surrounding repetitive head impacts that do not produce signs and symptoms of a concussion, as well as multiple concussions. Topics include short- and long-term outcomes, risk factors, neuropathology, and neuroimaging findings. Chapter 6 addresses interventions that may reduce the risk of sports-related concussions and includes discussions of the effectiveness of equipment such as helmets, mouthguards, and other devices; alternative playing surfaces; sport-specific rules and regulations; and legislation directed toward concussion education and athlete protection through policies governing athletes’ removal from and return to play following a suspected concussion. Chapter 7 contains the committee’s conclusions and recommendations.
The committee offers the following findings:
- The published literature includes numerous working definitions of concussion and inconsistent use of terminology (e.g., concussion, mTBI [despite the latter including more severe brain injury]), which pose challenges for interpreting and comparing findings across research studies on concussion.
- Concussion rates tend to be higher during competition than in practice (except for cheerleading), higher among female athletes than male athletes in comparable sports, and higher in certain sports.
- The National Collegiate Athletic Association Injury Surveillance System and High School RIO™ (Reporting Information Online) data systems are the only ongoing, comprehensive sources of sports-related injury data, including data on concussions, in youth athletes. Equivalent data are not available for athletes younger than high school age, nor are they available for participants in club sports or for youth engaging in competitive and recreational sports outside of an academic setting. There is no comprehensive system (individually or collectively) for acquiring accurate data on the incidence of sports- and recreation-related concussion across all youth age groups and sports.
- Data captured on sports- and recreation-related concussions do not routinely include race and ethnicity.
- There are no published data on the incidence of reported concussions during basic training for military recruits.
- Despite increased knowledge and a growing recognition in recent years that concussions involve some level of injury to the brain and therefore need to be diagnosed promptly and managed appropriately, there is still a culture among athletes and military personnel that resists the self-reporting of concussions and compliance with appropriate concussion management plans.
Agel, J., and E. J. Harvey. 2010. A 7-year review of men’s and women’s ice hockey injuries in the NCAA. Canadian Journal of Surgery 53(5):319-323.
Anderson, B. L., W. J. Pomerantz, J. K. Mann, and M. A. Gittelman. 2013. “I Can’t Miss the Big Game”: High School (HS) Football Players’ Knowledge and Attitudes about Concussions. Presented at the Pediatric Academic Societies Annual Meeting, Washington, DC, May 6.
AP (Associated Press). 2012. NFL, Army starts concussion program. http://espn.go.com/nfl/ story/_/id/8318684/nfl-teams-us-army-concussion-program (accessed August 5, 2013).
Aubry, M., R. Cantu, J. Dvoøák, T. Graf-Baumann, K. Johnston, J. Kelly, M. Lovell, P. McCrory, W. Meeuwisse, and P. Schamasch. 2002. Summary and agreement statement of the first International Conference on Concussion in Sport, Vienna 2001. British Journal of Sports Medicine 36(1):6-10.
Bakhos, L. L., G. R. Lockhart, R. Myers, and J. G. Linakis. 2010. Emergency department visits for concussion in young child athletes. Pediatrics 126(3):e550-e556.
Bazarian, J. J., P. Veazie, S. Mookerjee, and E. B. Lerner. 2006. Accuracy of mild traumatic brain injury case ascertainment using ICD-9 codes. Academic Emergency Medicine 13(1):31-38.
Becker, J., A. Runer, D. Neunhäuserer, N. Frick, H. Resch, and P. Moroder. 2013. A prospective study of downhill mountain biking injuries. British Journal of Sports Medicine 47(7):458-462.
BIAA (Brain Injury Association of America). 2011. BIAA adopts new TBI definition (February 6, 2011). http://www.biausa.org/announcements/biaa-adopts-new-tbi-definition (accessed March 28, 2013).
Boden, B. P., R. L. Tacchetti, R. C. Cantu, S. B. Knowles, and F. O. Mueller. 2007. Catastrophic head injuries in high school and college football players. American Journal of Sports Medicine 35(7):1075-1081.
Boden, B. P., I. Breit, J. A. Beachler, A. Williams, and F. O. Mueller. 2013. Fatalities in high school and college football players. American Journal of Sports Medicine 41(5): 1108-1116.
Cantu, R. C. 1998. Second-impact syndrome. Clinics in Sports Medicine 17(1):37-44.
Cantu, R. C., and R. Voy. 1995. Second impact syndrome a risk in any contact sport. Physician and Sportsmedicine 23(6):27-34.
CDC (Centers for Disease Control and Prevention). 2009. Heads up: Facts for physicians about mild traumatic brain injury (mTBI). http://www.cdc.gov/concussion/headsup/pdf/facts_for_physicians_booklet-a.pdf (accessed April 3, 2013).
CDC. 2012. Concussion and mild TBI. http://www.cdc.gov/concussion/index.html (accessed March 28, 2013).
CDC. 2013a. Concussion in sports. http://www.cdc.gov/concussion/sports/index.html (accessed March 28, 2013).
CDC. 2013b. Data Sources for WISQARS™ Nonfatal. http://www.cdc.gov/ncipc/wisqars/ nonfatal/datasources.htm#5.2 (accessed September 19, 2013).
CDC. 2013c. Heads up: Concussion in youth sports. http://www.cdc.gov/concussion/HeadsUp/youth.html (accessed July 2, 2013).
CDC. 2013d. National Health Interview Survey. http://www.cdc.gov/nchs/nhis/about_nhis.htm (accessed August 29, 2013).
Center for Injury Research and Policy. 2013. High School RIO™. http://www.nationwidechildrens.org/cirp-high-school-rio (accessed May 3, 2013).
Collins, M. W., M. R. Lovell, G. L. Iverson, R. C. Cantu, J. C. Maroon, and M. Field. 2002. Cumulative effects of concussion in high school athletes. Neurosurgery 51(5):1175-1181.
Collins, M. W., G. L. Iverson, M. R. Lovell, D. B. McKeag, J. Norwig, and J. Maroon. 2003. On-field predictors of neuropsychological and symptom deficit following sports-related concussion. Clinical Journal of Sports Medicine 13(4):222-229.
Congress of Neurological Surgeons. 1966. Committee on head injury nomenclature: Glossary of head injury. Clinical Neurosurgery 12:386-394.
Covassin, T., C. Swanik, and M. Sachs. 2003. Sex differences and the incidence of concussions among collegiate athletes. Journal of Athletic Training 38(3):238-244.
Covassin, T., R. Elbin, and Y. Nakayama. 2010. Examination of recovery time from sport-related concussion in high school athletes. Physician and Sportsmedicine 4(38):1-6.
Coyne, C. 2103. Experiencing Concussion in Youth Sports: An Athlete’s Perspective. Presentation before the committee, Seattle, WA, April 15.
CPSC (U.S. Consumer Product Safety Commission). 2013a. National Electronic Injury Surveillance System (NEISS). CPSC document #3002. http://www.cpsc.gov/en/Safety-Education/Safety-Guides/General-Information/National-Electronic-Injury-Surveillance-System-NEISS (accessed May 3, 2013).
CPSC. 2013b. NEISS Coding Manual. http://www.cpsc.gov/PageFiles/106513/completemanual.pdf (accessed June 4, 2013).
CPSC. 2013c. NEISS injury data: National Electronic Injury Surveillance System (NIESS). http://www.cpsc.gov/Research--Statistics/NEISS-Injury-Data (accessed May 3, 2013).
Daneshvar, D. H., C. J. Nowinski, A. C. McKee, and R. C. Cantu. 2011. The epidemiology of sport-related concussion. Clinical Journal of Sports Medicine 30(1):1-17. DOI:10.1016/j.csm.2010.08.006.
Datalys Center (Datalys Center for Sports Injury Research and Prevention, Inc.). 2013a. NATA NATION Preliminary Concussion Rates, 2010-2012. Institute of Medicine-National Research Council request. October 3.
Datalys Center. 2013b. NCAA Concussion Rates, 2004-2009 and 2009-2013. Institute of Medicine-National Research Council request. September 23.
Dick, R. W. 2009. Is there a gender difference in concussion incidence and outcomes? British Journal of Sports Medicine 43(Suppl I):i46-i50.
Dick, R., J. Agel, and S. W. Marshall. 2007. National Collegiate Athletic Association Injury Surveillance System commentaries: Introduction and methods. Journal of Athletic Training 42(2):173-182.
DoD (Department of Defense). 2012a. Instruction Number 6490.11. DoD Policy Guidance for Management of Mild Traumatic Brain Injury/Concussion in the Deployed Setting (September 18). http://www.usaisr.amedd.army.mil/assets/cpgs/DODI_6490.11_Policy_Guidance_for_Mgmt_of_Mild_Traumatic_Brain_Injury_or_Concussion_in_the_Deployed_Setting.pdf (accessed April 9, 2013).
DoD. 2012b. Population Representation in the Military Services: Fiscal Year 2010 Summary Report. http://prhome.defense.gov/rfm/MPP/ACCESSION%20POLICY/PopRep2010/ summary/PopRep10summ.pdf (accessed August 29, 2013).
DVBIC (Defense and Veterans Brain Injury Center). 2013. DoD worldwide numbers for TBI. http://www.dvbic.org/dod-worldwide-numbers-tbi (accessed June 27, 2013).
Echlin, P. S. 2012. Editorial: A prospective study of physician-observed concussion during a varsity university ice hockey season. Part 1 of 4. Neurosurgical Focus 33(6):E1:1-7.
Eisenberg, M. A., J. Andrea, W. Meehan, and R. Mannix. 2013. Time interval between concussions and symptom duration. Pediatrics. DOI: 10.1542/peds.2013-0432, originally published online June 10, 2013. http://pediatrics.aappublications.org/content/early/2013/06/05/peds.2013-0432 (accessed July 18, 2013).
Extreme Sport. 2008. Extreme sport growing in popularity. http://xtremesport4u.com/extreme-land-sports/extreme-sport-growing-in-popularity (accessed June 7, 2013).
Field, M., M. W. Collins, M. R. Lovell, and J. Maroon. 2003. Does age play a role in recovery from sports-related concussion? A comparison of high school and collegiate athletes. Journal of Pediatrics 142(5):546-553.
GAO (U.S. Government Accountability Office). 2009. Consumer Product Safety Commission: Better Data Collection and Assessment of Consumer Information Efforts Could Help Protect Minority Children. Report number GAO-09-731. Washington, DC: Government Printing Office.
Gessel, L. M., S. K. Fields, C. L. Collins, R. W. Dick, and R. D. Comstock. 2007. Concussions among United States high school and collegiate athletes. Journal of Athletic Training 42:495-503.
Gilchrist, J., K. E. Thomas, L. Xu, L. C. McGuire, and V. Coronado. 2011. Nonfatal traumatic brain injuries related to sports and recreation activities among persons ≤19 years—United States, 2001–2009. Morbidity and Mortality Weekly Report 60(39):1337-1342.
Giza, C. C., J. S. Kutcher, S. Ashwal, J. Barth, T. S. D. Getchius, G. A. Gioia, G. S. Gronseth, K. Guskiewicz, S. Mandel, G. Manley, D. B. McKeag, D. J. Thurman, and R. Zafonte. 2013. Evidence-Based Guideline Update: Evaluation and Management of Concussion in Sports. Report of the Guideline Development Subcommittee of the American Academy of Neurology. American Academy of Neurology.
Goldman, S. B. 2013. Army TBI Program Overview. Presentation before the committee, Washington, DC, February 25.
Halstead, M. E., K. D. Walter, and American Academy of Pediatrics, Council on Sports Medicine and Fitness. 2010. Sport-related concussion in children and adolescents. Pediatrics 126(3):597-615.
Halvorson, A. 2010. Understanding the Military: The Institution, the Culture, and the People. http://partnersforrecovery.samhsa.gov/docs/military_white_paper_final.pdf (accessed August 29, 2013).
Harmon, K. G., J. A. Drezner, M. Gammons, K. M. Guskiewicz, M. Halstead, S. A. Herring, J. S. Kutcher, A. Pana, M. Putakian, and W. O. Roberts. 2013. American Medical Society of Sports Medicine position statement: Concussion in sport. British Journal of Sports Medicine 47(1):15-26.
Hicks, R., J. Giacino, C. Harrison-Felix, G. Manley, A. Valadka, and E. A. Wilde. 2013. Progress in developing common data elements for traumatic brain injury research: Version two—the end of the beginning. Journal of Neurotrauma. September 9, doi:10.1089/neu.2013.2938.
Hinton, R. Y. 2012. Sports injury surveillance systems. Sports Medicine Update January/ February:2-7.
Hootman, J., R. Dick, and J. Agel. 2007. Epidemiology of collegiate injuries for 15 sports: Summary and recommendations for injury prevention initiatives. Journal of Athletic Training 42(2):311-319.
IOM (Institute of Medicine). 2002. Is Soccer Bad for Children’s Heads?: Summary of the IOM Workshop on Neuropsychological Consequences of Head Impact in Youth Soccer. Washington, DC: National Academy Press.
IOM. 2008. Gulf War and Health: Volume 7: Long-Term Consequences of Traumatic Brain Injury. Washington, DC: The National Academies Press.
IOM. 2011. Cognitive Rehabilitation Therapy for Traumatic Brain Injury: Evaluating the Evidence. Washington, DC: The National Academies Press.
IOM and NRC (National Research Council). 2000. From Neurons to Neighborhoods: The Science of Early Childhood Development. Washington, DC: National Academy Press.
IOM and NRC. 2001. Early Childhood Development and Learning: New Knowledge for Policy. Washington, DC: National Academy Press.
Kelly, T. 2013. Sports and Physical Training-Related Concussion in Military Personnel. Presentation before the committee, Washington, DC, February 25.
Knowles, S. B., K. L. Kucera, and S. W. Marshall. 2010. The injury proportion ratio: What’s it all about? Journal of Athletic Training 45(5):475-477.
Kontos, A. P., R. J. Elbin, V. C. Fazzio-Sumrock, S. Burkhart, H. Swindell, J. Maroon, and M. W. Collins. 2013. Incidence of sports-related concussion among youth football players aged 8-12 years. Journal of Pediatrics 163(3):717-720.
Kronisch, R. L., R. P. Pfeiffer, and T. K. Chow. 1996. Acute injuries in cross country and downhill road cycle racing. Medicine and Science in Sports and Exercise 28(11):1351-1355.
Kroshus, E., D. H. Daneshvar, C. M. Baugh, C. J. Nowinski, and R. C. Cantu. 2013. NCAA concussion education in ice hockey: An ineffective mandate. British Journal of Sports Medicine, in press. doi: 10.1136/bjsports-2013-092498.
Kyle, S. B., M. L. Nance, G. W. Rutherford, Jr., and F. K. Winston. 2002. Skateboard-associated injuries: Participation-based estimates and injury characteristics. Journal of Trauma-Injury Infection and Critical Care 53(4):686-690.
Langlois, J., W. Rutland-Brown, and M. Wald. 2006. The epidemiology and impact of traumatic brain injury: A brief overview. Journal of Head Trauma Rehabilitation 21(5): 375-378.
Lincoln, A., S. Caswell, J. Almquist, R. Dunn, J. Norris, and R. Hinton. 2011. Trends in concussion incidence in high school sports: A prospective 11-year study. American Journal of Sports Medicine 39(5):958-963.
Makdissi, M., R. C. Cantu, K. M. Johnston, P. McCrory, and W. H. Meeuwisse. 2013. The difficult concussion patient: What is the best approach to investigation and management of persistent (>10 days) postconcussive symptoms? British Journal of Sports Medicine 47(5):308-313.
Marar, M., N. McIlvain, S. Fields, and R. Comstock. 2012. Epidemiology of concussions among United States high school athletes in 20 sports. American Journal of Sports Medicine 40(4):747-755.
McClincy, M. P., M. R. Lovell, J. Pardini, M. W. Collins, and M. K. Spore. 2006. Recovery from sports concussion in high school and collegiate athletes. Brain Injury 20(1):33-39.
McCrea, M., T. Hammeke, G. Olsen, P. Leo, and K. M. Guskiewicz. 2004. Unreported concussion in high school football players: Implications for prevention. Clinical Journal of Sports Medicine 14(1):13-17.
McCrea, M., K. Guskiewicz, C. Randolph, W. B. Barr, T. A. Hammeke, S. W. Marshall, and J. P. Kelly. 2009. Effects of a symptom-free waiting period on clinical outcome and risk of reinjury after sport-related concussion. Neurosurgery 65(5):876-882; discussion 876-882.
McCrea, M., K. Guskiewicz, C. Randolph, W. B. Barr, T. A. Hammeke, S. W. Marshall, M. R. Powell, K. Woo Ahn, Y. Wang, and J. P. Kelly. 2013. Incidence, clinical course, and predictors of prolonged recovery time following sport-related concussion in high school and college athletes. Journal of the Inernational Neuropsychological Society 19(1):22-33.
McCrory, P. R., and S. F. Berkovic. 1998. Second impact syndrome. Neurology 50(3):677-683.
McCrory, P., K. Johnston, W. Meeuwisse, M. Aubry, R. Cantu, J. Dvoøák, T. Graf-Baumann, J. Kelly, M. Lovell, and P. Schamasch. 2005. Summary and agreement statement of the 2nd International Conference on Concussion in Sport, Prague 2004. British Journal of Sports Medicine 39(Suppl I):i78-i86.
McCrory, P., W. Meeuwisse, K. Johnston, J. Dvoøák, M. Aubry, M. Molloy, and R. Cantu. 2009. Consensus statement on concussion in sport: The 3rd International Conference on Concussion in Sport held in Zurich, November 2008. British Journal of Sports Medicine 43(Suppl 1):i76-i84.
McCrory, P., W. H. Meeuwisse, M. Aubry, B. Cantu, J. Dvoøák, R. J. Echemendia, L. Engebretsen, K. Johnston, J. S. Kutcher, M. Raftery, A. Sills, B. W. Benson, G. A. Davis, R. G. Ellenbogen, K. Guskiewicz, S. A. Herring, G. L. Iverson, B. D. Jordan, J. Kissick, M. McCrea, A. S. McIntosh, D. Maddocks, M. Makdissi, L. Purcell, M. Putukian, K. Schneider, C. H. Tator, and M. Turner. 2013a. Consensus statement on concussion in sport: The 4th International Conference on Concussion in Sport held in Zurich, November 2012. British Journal of Sports Medicine 47(5):250-258.
McCrory, P., W. H. Meeuwisse, R. J. Echemendia, G. L. Iverson, J. Dvoøák, and J. S. Kutcher. 2013b. What is the lowest threshold to make a diagnosis of concussion? British Journal of Sports Medicine 47(5):268-271.
Meehan, W. P., III, and R. Mannix. 2010. Pediatric concussions in United States emergency departments in the years 2002 to 2006. Journal of Pediatrics 157(6):889-893.
Menon, D. K., K. Schwab, D. W. Wright, and A. I. Maas, on behalf of The Demographics and Clinical Assessment Working Group of the International and Interagency Initiative toward Common Data Elements for Research on Traumatic Brain Injury and Psychological Health. 2010. Position statement: Definition of traumatic brain injury. Archives of Physical Medicine and Rehabilitation 91(11):1637-1640.
Middle School RIO™. 2013. http://www.nationwidechildrens.org/cirp-middle-school-rio (accessed June 28, 2013).
Mulligan, G. M., S. Hastedt, and J. C. McCarroll. 2012. First-Time Kindergartners in 2010-11: First Findings From the Kindergarten Rounds of the Early Childhood Longitudinal Study, Kindergarten Class of 2010-11 (ECLS-K:2011). NCES 2012-049.
NAE (National Academy of Engineering) and IOM. 2009. Systems Engineering to Improve Traumatic Brain Injury Care in the Military Health System Workshop Summary. Washington, DC: The National Academies Press.
NCAA (National Collegiate Athletic Association, Sports Sciences Institute). 2013. Concussion resources. http://www.ncaa.org/wps/wcm/connect/public/NCAA/SSI/Resources/concussion+resources/Partnership+strives+to+reduce+concussions+in+youth+football (accessed September 18, 2013).
NCSL (National Conference of State Legislatures). 2013. Traumatic brain injury legislation. http://www.ncsl.org/issues-research/health/traumatic-brain-injury-legislation.aspx (accessed October 4, 2013).
Network for Public Health Law. 2013. Summary matrix of state laws addressing concussions in youth sports (December 31, 2012). http://www.networkforphl.org/_asset/7xwh09/StateLawsTableConcussions_2-19-13.pdf (accessed October 4, 2013).
NFHS (National Federation of State High School Associations). 2013. Concussion in sports: What you need to know. http://www.nfhslearn.com/electiveDetail.aspx?courseID=38000 (accessed September 18, 2013).
NIH (National Institutes of Health). 2013. FITBIR informatics system. https://fitbir.nih.gov (accessed September 12, 2013).
NINDS (National Institute of Neurological Disorders and Stroke). 2013. NINDS common data elements: Traumatic brain injury, data standards. http://www.commondataelements.ninds.nih.gov/tbi.aspx#tab=Data_Standards (accessed September 12, 2013).
NRC. 1999. How People Learn: Brain, Mind, Experience, and School. Washington, DC: National Academy Press.
Pennington, B. 2013. Flubbing a baseline test on purpose is often futile. New York Times (May 6):D7. http://www.nytimes.com/2013/05/06/sports/sandbagging-first-concussion-test-probably-wont-help-later.html?_r=0 (accessed July 17, 2013).
PIPER Program (Pediatric Injury Prevention, Education and Research Program). 2013a. High School RIO™: Reporting Information Online. http://www.ucdenver.edu/academics/colleges/PublicHealth/research/ResearchProjects/piper/projects/RIO/Pages/default.aspx (accessed October 4, 2013).
PIPER Program. 2013b. High School RIO™ study reports. http://www.ucdenver.edu/academics/colleges/PublicHealth/research/ResearchProjects/piper/projects/RIO/Pages/Study-Reports.aspx (accessed October 4, 2013).
Pop Warner Little Scholars. 2012. 2012 Pop Warner Rule Book. Langhorne, PA: Pop Warner Little Scholars, Inc.
Powell, J. M., J. V. Ferraro, S. S. Dikmen, N. R. Temkin, and K. R. Bell. 2008. Accuracy of mild traumatic brain injury diagnosis. Archives of Physical Medicine and Rehabilitation 89(8):1550-1555.
Purcell, L., C. LeBlanc, M. McTimoney, J. Philpott, and M. Zetaruk. 2005. Sport readiness in children and youth. Paediatrics and Child Health 10(6):343-344.
Register-Mihalik, J. K., K. M. Guskiewicz, T. C. Valovich McLeod, L. A. Linnan, F. O. Mueller, and S. W. Marshall. 2013a. Knowledge, attitude, and concussion-reporting behaviors among high school athletes: A preliminary study. Journal of Athletic Training 48(5):645-653.
Register-Mihalik, J. K., L. A. Linnan, S. W. Marshall, T. C. Valovich McLeod, F. O. Mueller, and K. M. Guskiewicz. 2013b. Using theory to understand high school aged athletes’ intentions to report sport-related concussion: Implications for concussion education initiatives. Brain Injury 27(7-8):878-886.
Sapien, J., and D. Zwerdling. 2012. Army study finds troops suffer concussions in training. http://www.propublica.org/article/army-study-finds-troops-suffer-concussions-intraining#comments (accessed June 7, 2013).
Saunders, R. L., and R. E. Harbaugh. 1984. Second impact in catastrophic contact-sports head trauma. JAMA 252(4):538-539.
Schultz, M. R., S. W. Marshall, F. O. Mueller, J. Yang, N. L. Weaver, W. D. Kalsbeek, and J. M. Bowling. 2004. Incidence and risk factors for concussion in high school athletes, North Carolina, 1996–1999. American Journal of Epidemiology 160(10):937-944.
Sun, J. F. 2013. See where your state stands on concussion law. http://usafootball.com/news/featured-articles/see-where-your-state-stands-concussion-law (accessed October 4, 2013).
Thomas, M., T. S. Haas, J. J. Doerer, J. S. Hodges, B. O. Aicher, R. F. Garberich, F. O. Mueller, R. C. Cantu, and B. J. Maron. 2011. Epidemiology of sudden death in young, competitive athletes due to blunt trauma. Pediatrics 128(1):e1-e8.
Thurman, D. J., C. M. Branche, and J. E. Sniezek. 1998. The epidemiology of sports-related traumatic brain injuries in the United States: Recent developments. Journal of Head Trauma Rehabilitation 13(2):1-8.
Thurmond, V. A., R. Hicks, T. Gleason, A. C. Miller, N. Szuflita, J. Orman, and K. Schwab. 2010. Advancing integrated research in psychological health and traumatic brain injury: Common data elements. Archives of Physical Medicine and Rehabilitation 91(11): 1633-1636.
Torres, D. M., K. M. Galetta, H. W. Phillips, E. M. S. Dziemianowicz, J. A. Wilson, E. S. Dorman, E. Laudano, S. L. Galetta, and L. J. Balcer. 2013. Sports-related concussion: Anonymous survey of a collegiate cohort. Neurology Clinical Practice 3(4):279-287.
Tsao, J. W. 2013. Navy and Marine Corps TBI Efforts. Presentation before the committee, Washington, DC, February 25.
USA Football. 2013a. Concussion awareness. http://usafootball.com/health-safety/concussionawareness (accessed September 18, 2013).
USA Football. 2013b. USA Football releases preliminary data in study examining youth football player health and safety. News Release, May 20. http://usafootball.com/health-safety/usa-football-releases-preliminary-date-study-examining-youth-football-player-health-an (accessed July 25, 2013).
USA Hockey. 2011. 2011-2013 Official Rules of Ice Hockey. Colorado Springs, CO: USA Hockey, Inc.
USA Hockey. 2013. Concussion information. http://www.usahockey.com/page/show/908034-concussion-information (accessed September 18, 2013).
USSSA Baseball (U.S. Specialty Sports Association Baseball). 2013. Official Baseball National By-Laws & Rules. Kissimmee, FL: U.S. Specialty Sports Association.
Vergun, D. 2012. NFL, Army both work to combat traumatic brain injury. http://www.army.mil/article/86544 (accessed August 5, 2013).
Wilde, E. A., S. R. McCauley, G. Hanten, G. Avci, A. P. Ibarra, and H. S. Levin. 2012. History, diagnostic considerations, and controversies. In Mild Traumatic Brain Injuries in Children and Adolescents: From Basic Science to Clinical Management, edited by M. Kirkwood and K. O. Yeates. New York: Guilford Press. Pp. 3-21.
Wolfe, C. L. 2013. West Point health care providers focus on brain injury prevention, diagnosis, treatment. (March 28). http://www.army.mil/article/99664 (accessed July 25, 2013).
Wolverton, B. 2013. Coach makes the call. Chronicle of Higher Education (September 2). http://chronicle.com/article/Trainers-Butt-Heads-With/141333?cid=megamenu (accessed September 15, 2013).
YSSA (Youth Sports Safety Alliance). 2013. Secondary School Student Athletes’ Bill of Rights. http://www.youthsportssafetyalliance.org/docs/Athletes-Bill-of-Rights.pdf (accessed August 5, 2013).