Incidence of sport-related traumatic brain injury and risk factors of severity: a population-based epidemiologic study

Abstract

Purpose

Few studies of sport-related traumatic brain injury (TBI) are population-based or rely on directly observed data on cause, demographic characteristics, and severity. This study addresses the epidemiology of sport-related TBI in a large population.

Methods

Data on all South Carolina hospital and emergency department encounters for TBI, 1998–2011, were analyzed. Annual incidence rate of sport-related TBI was calculated, and rates were compared across demographic groups. Sport-related TBI severity was modeled as a function of demographic and TBI characteristics using logistic regression.

Results

A total of 16,642 individuals with sport-related TBI yielded an average annual incidence rate of 31.5/100,000 population with a steady increase from 19.7 in 1998 to 45.6 in 2011. The most common mechanisms of sport-related TBI were kicked in football (38.1%), followed by fall injuries in sports (20.3%). Incidence rate was greatest in adolescents ages 12-18 (120.6/100,000/persons). Severe sport-related TBI was strongly associated with off-road vehicular sport (odds ratio [OR], 4.73; 95% confidence interval [95% CI], 2.92−7.67); repeated head trauma (OR, 4.36; 95% CI, 3.69−5.15); equestrian sport (OR, 2.73; 95% CI, 1.64−4.51); and falls during sport activities (OR, 2.72; 95% CI, 1.67−4.46).

Conclusions

The high incidence of sport-related TBI in youth, potential for repetitive mild TBI, and its long-term consequences on learning warrants coordinated surveillance activities and population-based outcome studies.

Introduction

Each year, 1.7 million Americans experience traumatic brain injury (TBI), with 275,000 hospitalizations and 52,000 deaths occurring as a result [1]. TBI, including concussion, can lead to chronic and long-term disability [2]. Population-based studies indicate ∼40% of TBI survivors developed persistent functional deficits within a year [3], [4]. Population-based studies of sports and recreation-related TBI (sport-TBI) are sparse and yield equivocal results. For example, incidence rates of sport-TBI derived from data sources that are not representative of the base population yield widely discrepant annual estimates ranging from 2.6/100,000 to 124/100,000 population [5], [6]. Differing target populations and case ascertainment criteria resulted in wide variation in estimates, and risk factors for severity of sport-TBI are inadequately evaluated [7]. Most published studies are based on self-report from household surveys, various data sources lacking uniform variable definition, or targeted surveys from athletics programs in high schools and colleges [8], [9], [10], [11].

Many studies of sport-TBI focused on professional athletes, high school, and college players; specific types of sport; or specific TBI type (mainly concussions) and relied on reports of coaches, athletic trainers, and trained observers with emphasis on evaluating kinematics and time elapsing before returning to play [10], [11], [12], [13], [14], [15], [16], [17]. These studies report incidence rates based on exposure time and play seasons as the denominator, which hamper comparability with population-based rate estimates [18]. Nonetheless, the greater incidence of concussion in contact sports such as football and rugby, gender differences as a function of the type of sport, and greater risk of TBI with repetitiveness of head trauma have been reported from these studies [10], [15], [16], [18], [19], [20], [21].

Although the estimates of sport-TBI in the literature vary widely, researchers agree on the increasing trend during the past 20 years [19], [20], [22]. This trend may be attributed to (1) increased case detection because of heightened awareness of the deleterious effects of concussions and mild TBI on memory and behavior; (2) stricter regulation in reporting sport injuries; and (3) increased awareness of the beneficial effects of physical activity in health-seeking behavior, in turn promoting greater participation in sport activities and free plays in communities [20], [22], [23], [24].

Our study addresses gaps in the literature of sport-TBI by using data from an ongoing surveillance program of central nervous system trauma that receives detailed information on all clinical encounters in a statewide population with uniform coding criteria and data definitions. The study used external cause of injury codes (E-codes) specific to sport injuries, in combination with E-codes that indicate places of occurrence to arrive at a conservative but reasonably accurate population-based incidence rates in a statewide population. Specifically, we examined the mechanisms by which injuries occurred, TBI type, frequency of TBI (repetitiveness), and severity of TBI to identify high-risk population groups. The study hypothesizes that persons with previous TBI and older individuals are more likely to have severe sport-TBI than those without any evidence of previous TBI and youngest age group.