(Editor’s Note: What follows is an excerpt from a recent released book written by Dr. Brian Hainline, the Chief Medical Officer of the NCAA, and Dr. Robert Stern. The book can be purchased at https://www.elsevier.com/books/sports-neurology/hainline/978-0-444-63954-7, or https://www.amazon.com/Sports-Neurology-158-Handbook-Clinical/dp/0444639543)
Chapter 7: Epidemiology of sports concussion in the United States
By GRANT T. BALDWIN and MATTHEW J. BREIDING (National Center for Injury Prevention and Control, Centers for Disease Control and Prevention, Division of Unintentional Injury Prevention, Atlanta, GA, United States), and R. DAWN COMSTOCK (Department of Epidemiology, Colorado School of Public Health, Aurora, CO, United States)
Abstract
Sports and recreation-related (SRR) activities are common in the United States. Beyond the benefits to health, SRR activities can create new friendships, give people a sense of belonging, foster teamwork and other leadership skills, and develop sportsmanship and a respect for rules that govern play. Public awareness about the risk of concussion has grown as the long-term consequences of traumatic brain injury (TBI) have become better known, and likely explains the increasing concussion incidence rates. Currently, surveillance systems capture SRR concussions among high school and college athletes participating in sanctioned sports. National estimates of SRR TBI presenting to an emergency department also exist. Persons under the age of 19 sustain a majority of SRR concussions. Concussion risk is greatest for boys in contact/collision sports like football, ice hockey, and lacrosse, and is more likely to occur in competition versus practice settings. Girls have elevated concussion rates in gender-comparable sports. Despite better data, concussions are still underreported, undermanaged, and often not properly identified. This is especially true for concussions occurring outside organized sports, in nonsport recreational activities, and for concussions either not seen or evaluated in nonemergency department settings. A new surveillance system proposed by the Centers for Disease Control and Prevention aims to fill the gap.
Introduction
This chapter explores the epidemiology of sports concussion in the United States. After briefly defining concussion and participation levels in sports and recreation-related (SRR) concussion-prone activities, we outline measures of burden and risk for concussion. We look at data systems used in the United States to capture concussions and identify gaps in these systems. Next, we look at concussion incidence across a variety of demographic characteristics and other features. This includes describing differences in concussion incidence by age, gender, sport, or recreational activity, and whether the concussion happened during a game or in a practice setting. Finally, we make recommendations on methods for obtaining more comprehensive, detailed, timely, and actionable sports concussion data.
Definition of Concussion
A concussion is a type of mild traumatic brain injury (TBI) caused by a bump, blow, or jolt to the head or body that can change the way the brain normally works (Centers for Disease Control and Prevention, 2016). Typically, a concussion results in a rapid onset of a short-lived impairment in neurologic function (McCrory et al., 2017). Most people who sustain a concussion recover within 1—3 weeks (McCrory et al., 2017). However, for some people, persistent symptoms such as headaches, amnesia, irritability, slowed reaction times, and insomnia can last for several weeks, months, or longer (Ellis et al., 2016; McCrory et al., 2017). Recovery can be more protracted as the severity of the injury increases and among those with a history of previous concussion (McCrory et al., 2017) (see Chapter 17). Approximately 10—15% of athletes have persistent concussion-related symptoms, but this percentage may be higher in select sports like ice hockey or in vulnerable populations like children (Makdissi et al., 2013). Younger athletes may be more susceptible to concussions due to their larger head-to-body ratio and weaker neck muscles (Pfister et al., 2016). Younger athletes may also be more susceptible to severe acute and longer-term complications following a concussion, given the rapid neurodevelopment that occurs throughout adolescence (Patel and Greydanus, 2002; Patel et al., 2005). Concussion symptoms can affect all aspects of a person’s life — at home, at school, at work, and during sports or recreational activities.
Participation in Sports and Recreation
The following sections outline estimates of participation in sports and recreation across the lifespan to provide a perspective on the number of persons who might be at risk for one or more concussions.
Children and adolescents: There are approximately 60 million children participating in organized youth sports (National Council for Youth Sports, 2017). Boys tend to participate in more team activities, while girls tend to participate in more noncompetitive or individualized activities (Song et al., 2015). Physical activity is highest among non-Hispanic white children and those of normal or below-normal body mass index (Song et al., 2015). Overall, approximately 57% of children in the United States 6—12 years old participated in a team sport in 2015 (Aspen Institute, 2016). Among children playing sports, those with the highest participation included basketball (14.7%), baseball (13.2%), outdoor soccer (8.9%), and tackle football (3.3%) (Aspen Institute, 2016).
Beyond organized sports, about 25% of American youth 12—15 years of age participate in daily moderate to vigorous physical activity — inside or outside school — for at least 60 minutes per day (Fakhouri et al., 2014). In contrast, about 7% of youth 12—15 years of age reported no moderate to vigorous physical activity on any day of the week (Fakhouri et al., 2014). Among active boys, the top five most popular forms of physical activity were basketball (48%), running (33.5%), football (27.4%), bicycle riding (24%), and walking (23.6%) (Fakhouri et al., 2014). Among girls, the top five most popular forms of physical activity were running (34.9%), walking (27.6%), basketball (21.4%), dancing (20.8%), and bike riding (18.4%) (Fakhouri et al., 2014).
High school athletes: Of the 16.5 million high school students in the United States, 7.8 million participated in school-sanctioned sports in the 2014—2015 academic year — including 4.5 million boys and 3.3 million girls (National Federation of High School Associations, 2015; United States Census, 2015). Among the 12 sports listed in Table 7.1, there are almost 5 million participants in high school sports that will be highlighted later in the chapter. These are the sports whose concussion incidence is higher than other high school-sanctioned sports.
College athletes: Sports participation in National Collegiate Athletic Association (NCAA) sports has never been higher for both male and female student-athletes (Tables 7.2 and 7.3). In the 2015—2016 academic year, there were approximately 487,000 student-athletes (275,000 male and 212,000 female) (Irick, 2016). This represents an increase of 23.7% from the 2005—2006 academic year, when there were approximately 394,000 student-athletes (Irick, 2016). The increase in participation by female student-athletes slightly outpaced their male counterparts (25.722.3%) (Irick, 2016). Overall, there are over 19,300 women’s and men’s sports teams across NCAA member institutions (Irick, 2016). Based on the number of participants in Tables 7.2 and 7.3, there are approximately 283,000 athletes in NCAA sports that will be highlighted later in the chapter. These are the sports whose concussion incidence is higher than other NCAA sports.
Adult athletes: Currently, there are approximately 247 million Americans over the age of 18 (United States Census, 2015). Approximately 25% of American adults over the age of 18 participate in some form of leisure-time physical activity each month, and 10% participate in four or more activities (Dai et al., 2015). Unfortunately, 38% of American adults engage in no leisure-time physical activity (Dai et al., 2015). There is substantial variation in physical activity participation by gender, age, race, and education. Overall, males, younger Americans, non-Hispanic white adults, college-educated adults, and those with a normal or below-normal body mass index are the most physically active (Dai et al., 2015; Watson et al., 2015). There is also variation in participation by type of activity (Table 7.4). Finally, there is significant variation in how often adults report participating in these activities weekly, but most adults report participating in a minimum of 90 minutes per week for their selected physical activity (Dai et al., 2015).
Table 7.1: Participation in high school athletics among select sports — United States, 2014—2015
Sport and number of participants (in thousands)
Football — 11-player
1085
Wrestling
270
Basketball
971
Lacrosse
193
Soccer
808
Competitive spirit squads
128
Baseball
488
Field hockey
61
Volleyball
487
Ice hockey
45
Softball — fast pitch
366
Gymnastics
21
Reproduced from National Federation of State High School Associations (2015) Participation statistics. Available online at: http://www.nfhs.org/ParticipationStatics/ParticipationStatics.aspx/ (accessed May 21, 2017).
Table 7.2: Participation in men’s collegiate athletics among select sports — United States, 2015—2016
Sport and number of participants (in thousands)
Football
73.7
Wrestling
7.1
Baseball
34.6
Ice hockey
4.1
Soccer
24.8
Volleyball
1.9
Basketball
18.7
Skiing
0.4
Lacrosse
13.4
Gymnastics
0.3
Reproduced from Irick E (2016) Student-athlete participation 1981-1982—2015-16. NCAA sport sponsorship and participation rates report. Indianapolis, IN: The National Collegiate Athletic Association. Available online at: http://www.ncaapublications.com/ productdownloads/PR1516.pdf (accessed June 8, 2017).
Table 7.3: Participation in women’s collegiate athletics among select sports — United States — 2015—2016
Sport and number of participants (in thousands)
Soccer
27.4
Field hockey
6.0
Softball
19.7
Ice hockey
2.3
Volleyball
17.1
Gymnastics
1.5
Basketball
16.6
Equestrian
1.4
Lacrosse
11.4
Sand volleyball
0.9
Reproduced from Irick E (2016) Student-athlete participation 1981-1982—2015-16. NCAA sport sponsorship and participation rates report. Indianapolis, IN: The National Collegiate Athletic Association. Available online at: http://www.ncaapublications.com/ productdownloads/PR1516.pdf (accessed June 8, 2017).
Table 7.4: Prevalence of adult participation in select leisure-time physical activities in the past 30 days by sex — National Health and Nutrition Examination Survey 1999—2006
Participation
Total
Male
Female
(%)
(%)
(%)
Sports
19.4
28.3
11.1
Dancing/aerobics
13.9
9.0
18.5
Bicycling
11.6
13.8
9.5
Basketball
5.9
10.2
1.9
Baseball/softball
2.5
3.9
1.2
Soccer
1.8
3.0
0.7
Football
1.6
2.7
0.5
Skating/rollerblading
1.6
1.7
1.5
Volleyball
1.2
1.4
1.1
Skiing
1.0
1.0
1.0
Martial arts
0.7
1.1
0.4
Horseback riding
0.6
0.5
0.7
Racquetball
0.6
1.0
0.2
Wrestling
0.5
0.8
—
Boxing
0.4
0.8
0.1
Hockey
0.3
0.6
—
Dai S, Carroll DD, Watson KB et al. (2015). Participation in types of physical activities among US adults—National Health and Nutrition Examination Survey 1999—2006. J Phys Act Health 12(6 Suppl 1): S128—S140.
Sports include baseball/softball, basketball, bowling, boxing, foot- ball, frisbee, golf, hockey, horseback riding, martial arts, racquetball, skating/rollerblading, soccer, tennis, volleyball, and wrestling.
Grant T. Baldwin can be reached at National Center for Injury Prevention and Control, Centers for Disease Control and Prevention, Division of Unintentional Injury Prevention, 4770 Buford Hwy NE F-62, Atlanta GA 30341, United States. Tel: +1-770- 488-1436, E-mail: gfb3@cdc.gov
