.. ation in mental status, not necessarily resulting in a loss of consciousness, were included. Athletic trainers initially identified the majority of suspected concussions, and respective team physicians performed the examinations and made the final decisions. Once the diagnosis was established, neuropsychological testing was administered as soon as possible following injury (within 24 hours in all cases). The neuropsychological tests and self-report inventory used in the postinjury phase were identical to those used at baseline, although alternate and reliable forms of the HVLT and COWAT were administered to minimize learning effects associated with these measures. Football players from within the sample served as controls.
Control athletes were matched with athletes who sustained concussion according to ACT/SAT scores, history of LD, history of previous concussion, institution, and playing position. In addition, to control for exertion, each control athlete was tested within the same time frame as the athletes who experienced concussion (eg, following a game or practice). Within the context of these variables, it was possible for controls to be matched to more than 1 player with concussion. No control athlete experienced a concussion during the course of the study. Controls were excluded from further study. Data Analysis Data from the 4 universities were pooled and analyzed using Statistica Version 5.1 statistical software for Windows.23 To explore the relationship between prior history of concussion, diagnosis of LD, and neuropsychological baseline performance, multiple analysis of variance (MANOVA) was performed.
Concussion history (no prior concussion vs 1 vs 2 concussions) and LD (positive or negative diagnosis) were entered as independent variables, and cognitive and symptom total scores were entered as dependent measures. The MANOVA design was selected to allow an analysis of performance differences between the athletes with different concussion and LD histories, across multiple neuropsychological domains. This design also permitted an analysis of possible interaction effects between concussion and LD histories. For in-season (postconcussion) data, a discriminant function classification analysis was conducted to determine the accuracy of the neuropsychological test battery in separating athletes with concussions from control athletes within 24 hours of concussion. The 8 tests constituting the neuropsychological test battery were used as predictor variables, and membership in the group with concussions or control group was used as the dependent (grouping) variable. To provide preliminary information regarding the recovery pattern of athletes with concussions relative to the control group and to their own baseline performance, standard scores were created to convert the selected neuropsychological test scores to a common metric. These standard scores were constructed so that baseline performance for each group would have a mean of 100 and SD of 15.21 Group differences of one-half SD (7.5 standard score units) are considered to reflect at least a moderate difference between the means.22 Any deviation from 100 indicates a change in performance relative to baseline for each group.
The recovery pattern of players who sustained concussion across different time intervals was evaluated by standardizing all neuropsychological test results and comparing performance of the athletes with concussion with controls’ performance within 24 hours, and at 3, 5, and 7 days postinjury. RESULTS Demographic Data and Concussion History The multiuniversity sample included 393 male football players with a mean (SD) age of 20.4 (1.7) years and 2.6 (1.3) mean (SD) years in college. Forty-six percent of the sample was African American, 48% European American, 4% Polynesian American, 1% Asian American, and 1% Hispanic American. Of the 393 players, 6% (n=25) were quarterbacks; 8% (n=33), running backs; 13% (n=52), wide receivers; 16% (n=64), offensive linemen; 6% (n=23), tight ends; 17% (n=67), defensive backs; 16% (n=61), defensive linemen; 13% (n=48), linebackers; and 5% (n=20), kickers. Of the players completing the ACT examination to qualify for college admission (n=180), the mean (SD) score was 20.0 (1.7).
Of those qualifying with the SAT (n=200), the mean (SD) score was 952.9 (149.1). College admission scores were missing for 13 individuals. Three players in the sample reported a documented history of diagnosed psychiatric illness (eg, bipolar disorder and major depression). These players completed the baseline evaluation, but were excluded from further study. No player in the sample reported a diagnosis of major neurological disorder or history of abuse of alcohol or other drugs.
Forty-six percent (n=179) of the sample reported no prior history of concussion, 34% (n=129) reported experiencing 1 concussion of any grade, and 20% (n=79) reported a history of 2 or more sustained concussions (range, 2-10) of any grade. A significant relationship was found between total years participating in football and total number of concussions sustained (r=0.15; P.02). Quarterbacks (17 of 25) and tight ends (15 of 23) had the the highest rates of prior concussion (68% and 65%, respectively). Running backs-fullbacks (11 of 33) and kickers-punters experienced the lowest rates of prior concussion (33% and 46%, respectively). The prevalence of LD within the total sample of 393 athletes was 13.5% (n=53).
Of the players with no history of concussion (n=179), 10.6% (n=19) had a diagnosed LD; of those who had experienced 1 prior concussion (n=129), 14.7% (n=19) had diagnosed LD, and of those who had experienced multiple concussions (n=79), 19.0% (n=15) had a diagnosed LD. Although these data suggest a possible trend between history of LD and history of multiple concussions, this relationship was not statistically significant (2=3.74; P=.15). Previous Concussions, LD History, and Baseline Neuropsychological Performance The MANOVA yielded significant main effects for both LD (F=4.57; P*.001) and concussion history (F=1.91; P=.009) on neuropsychological test results, which indicated that both of these variables were significantly related to overall neuropsychological performance. The interaction of LD and concussion history was not significant (F=1.17; P=.28). A follow-up series of univariate F tests was completed to identify the specific neuropsychological measures that accounted for the significant MANOVA. Tests for the LD main effect were Trails B (F=15.98;P*.001); SDMT (F=22.9; P*.001); COWAT (F=11.6; P*.001); and Hopkins delayed memory (F=11.8; P*.001). For the history of concussion main effect, significant tests included Trails B (F=6.1; P=.002); SDMT (F=7.8; P*.001); and total symptoms reported (F=4.6; P=.01).
To evaluate concussion group differences on the neuropsychological tests, additional post hoc analyses were conducted using the Tukey Honest Significant Difference test for unequal subjects.24 Table 1 presents the group means (SDs) for athletes. The group with no history of concussion reported fewer symptoms than both the single concussion group (P=.04) and the multiple concussion group (P*.001) on the concussion symptom inventory. Baseline symptoms increased as the number of concussions increased. On Trails B, the multiple concussion group performed significantly worse at baseline than the group with no history of concussion (P=.02) and the single concussion group (P*.001). Baseline data also differed significantly on the SDMT with the multiple concussion group performing worse than both the group with no history of concussion (P=.008) and the single concussion group (P*.001). These findings are not attributed to preexisting group differences in terms of aptitude as the multiple concussion group had higher SAT and ACT scores than did the group with no history of concussion and the single concussion group.
The table presents demographic and neuropsychological test data for the group with LD and the group without LD. To investigate the interplay between concussion history and LD on baseline neuropsychological test performance, a concussion history and LD interaction term was constructed. Univariate F tests for all 10 neuropsychological variables demonstrated statistically significant interactions for Trails B (F=4.99; P=.007) and SDMT (F=4.74; P=.009). In both cases, athletes with a history of multiple concussions and LD performed significantly worse than did athletes with no history of LD who had experienced multiple concussions (Figure 1). In-Season Concussions Nineteen players in the study sample were diagnosed by team medical staff as sustaining a concussion during the course of the 1997-1999 seasons. Thirteen individuals sustained a grade 1 concussion (mental status abnormalities resolved within 15 minutes), 4 athletes sustained a grade 2 concussion (mental status abnormalities that lasted longer than 15 minutes, but resolved within 45 minutes), and 2 athletes sustained a grade 3 concussion (brief [approximately 5-10 seconds] loss of consciousness).
The time between baseline testing and in-season c Bibliography Michael W. Collins, PhD; Scott H. Grindel, MD; Mark R. Lovell, PhD; Duane E. Dede, PhD; David J. Moser, PhD; Benjamin R. Phalin, BS; Sally Nogle, MA, ATC; Michael Wasik, MEd, ATC; David Cordry, MA; Michelle Klotz Daugherty, MA; Samuel F.
Sears, PhD; Guy Nicolette, MD; Peter Indelicato, MD; Douglas B. McKeag, MD.