Injuries In Sports Despite the high prevalence and potentially serious outcomes associated with concussion in athletes, there is little systematic research examining risk factors and short- and long-term outcomes. Objectives To assess the relationship between concussion history and learning disability (LD) and the association of these variables with neuropsychological performance and to evaluate postconcussion recovery in a sample of college football players. Design, Setting, and Participants A total of 393 athletes from 4 university football programs across the United States received preseason baseline evaluations between May 1997 and February 1999. Subjects who had subsequent football-related acute concussions (n=16) underwent neuropsychological comparison with matched control athletes from within the sample (n=10). Main Outcome Measures Clinical interview, 8 neuropsychological measures, and concussion symptom scale ratings at baseline and after concussion. Results Of the 393 players, 129 (34%) had experienced 1 previous concussion and 79 (20%) had experienced 2 or more concussions. Multivariate analysis of variance yielded significant main effects for both LD (P*.001) and concussion history (P=.009), resulting in lowered baseline neuropsychological performance.
A significant interaction was found between LD and history of multiple concussions and LD on 2 neuropsychological measures (Trail-Making Test, Form B [P=.007] and Symbol Digit Modalities Test [P=.009]), indicating poorer performance for the group with LD and multiple concussions compared with other groups. A discriminant function analysis using neuropsychological testing of athletes 24 hours after acute in-season concussion compared with controls resulted in an overall 89.5% correct classification rate. Conclusions Our study suggests that neuropsychological assessment is a useful indicator of cognitive functioning in athletes and that both history of multiple concussions and LD are associated with reduced cognitive performance. These variables may be detrimentally synergistic and should receive further study. JAMA.
1999;282:964-970 The management of mild traumatic brain injury (MTBI; eg, concussion, defined as a traumatically induced alteration in mental status not necessarily resulting in loss of consciousness) in athletics is currently one of the most compelling challenges in sports medicine. Despite the high prevalence1 and potentially serious outcomes2, 3 associated with concussion, systematic research on this topic is lacking. Many sports medicine practitioners are not satisfied with current return-to-play and treatment options, which do not appear to be evidence based.4-6 There is also little research examining whether long-term cognitive morbidity is associated with concussion. Past research with nonathletes revealed that repeated concussions appear to impart cumulative damage, resulting in increasing severity and duration with a second MTBI occurring within 48 hours.7 No data were presented which addressed more long-term outcomes. Although survey data have shown that a prior history of head injury increases the risk for sustaining subsequent MTBI,8 other potential risk factors associated with sports-related concussion have not been identified. Learning disability (LD), the etiology of which is presumably secondary to central nervous system dysfunction,9 refers to a heterogeneous group of disorders manifested by difficulties in the acquisition and use of listening, speaking, writing, reading, reasoning, or mathematical abilities and which is traditionally diagnosed in early childhood.10, 11 The incidence of diagnosed LD is 11.8% in the general university population.12 However, no study to date has addressed whether LD may represent a risk factor (such as that seen with prior head injury) for poor outcome following sports-related MTBI in college athletes.
Previous research has outlined the reliability, validity, and sensitivity of neuropsychological tests in assessing the specific cognitive areas associated with MTBI in the general population.13-15 To date, 3 published studies have examined the use of neuropsychological testing in US football players.16-18 The only multicenter study16 was conducted in the mid-1980s and was designed to address the acute effects of concussion. The current study was designed to address 2 issues: first, to investigate whether a relationship exists between prior concussion and diagnosed LD among college football players and determine the influence of these variables, in isolation and combination, on baseline neuropsychological performance; and second, to evaluate the use of a neuropsychological test battery in diagnosing concussion and delineating recovery of cognitive function following MTBI in athletes. METHODS Subjects Participants in this study consisted of 393 male college football players from 4 Division IA football programs: Michigan State University, East Lansing (n=119); the University of Florida, Gainesville (n=106); the University of Pittsburgh, Pittsburgh, Pa (n=85); and the University of Utah, Salt Lake City (n=83). At the initial preseason baseline session, the following self-reported data were collected: age, playing position, SAT/ACT scores (Scholastic Aptitude Test/American College Testing, ie, college entrance examination scores), history of LD, neurological history (eg, central nervous system neoplasm or epilepsy), history of psychiatric illness (eg, depression and/or mania or anxiety), history of alcohol and/or drug abuse, prior sports played, and history of concussion. Educational records at each institution were used to verify a documented history of diagnosed LD. A standardized concussion history form was administered at baseline to obtain detailed information regarding previous concussions, year of concussion, description of incident, nature and duration of relevant symptoms (eg, confusion and/or disorientation, retrograde and/or anterograde amnesia, and loss of consciousness), neuroimaging results (if any), and days lost from participation in football (if any).
Athletes who reported amnesia were asked to provide any known collateral information from the athletic trainer, sports-medicine physician, or other source familiar with the details of the incident. All previous concussions were classified using the practice parameter of the American Academy of Neurology.19 Protocol and Outcome Measures Preseason Baseline Evaluation Appropriate review for research with human subjects was granted separately from the 4 institutions at which the participants were enrolled. Each participant provided written informed consent for voluntary participation. All data collection was completed by the research team of clinical neuropsychologists (clinicians with PhDs or doctoral-level students) or team physicians or athletic trainers who were thoroughly trained in the use of the measures. Each examiner was required to attend a 2-hour workshop and was supervised during test adminstration (by M.W.C.) to facilitate the appropriate standardized administration of the test battery.
All measures were administered and scored in a standardized manner to minimize differences between test administrators and institutions. Project investigators trained in neuropsychological assessment completed all data scoring and interpretation. Baseline data collection at 3 universities (Michigan State University, University of Pittsburgh, and University of Florida) was completed prior to the 1997/98 and 1998/99 football seasons during the months of May to August. Baseline data collection at the University of Utah occurred during February 1999 for the 1999/2000 season (only baseline data from the University of Utah were used for analyses). Approximately 95% of all roster football players (scholarship and scout team players) voluntarily participated in the project. At these baseline sessions, demographic and player history information was obtained via interview.
Each athlete was then administered a battery of neuropsychological tests (approximately 30 minutes in length) that is used by the National Football League.17, 20 Tests in the battery were the Hopkins Verbal Learning Test (HVLT; verbal learning, delayed memory); Trail-Making Tests, Forms A and B (Trails A and Trails B; visual scanning and executive functioning); Digit Span Test (attention and concentration); Symbol Digit Modalities Test (SDMT; information processing speed); Grooved Pegboard Test, dominant and nondominant hand (bilateral fine motor speed); and the Controlled Oral Word Association Test (COWAT; word fluency). This test battery, described in detail elsewhere,17 was constructed to evaluate multiple aspects of cognitive functioning. In addition to neuropsychological testing, athletes also completed the Concussion Symptom Scale17 to assess a baseline level of self-reported symptoms. This Likert scale consists of 20 symptoms commonly associated with concussion (eg, headache, dizziness, and trouble falling asleep), with symptoms ranging from none (score, 0) to severe (score, 6). Postconcussion Evaluation Athletes who sustained a concussion during the course of a season underwent serial neuropsychological evaluations following the incident (within 24 hours of the incident, and at days 3, 5, and 7 postinjury). Concussion was defined according to the American Academy of Neurology practice parameter.19 Thus, players experiencing a traumatically induced alter …