Injuries In Sports Essay, Research Paper
Relationship Between Concussion and
Neuropsychological Performance in College
Football Players
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
Context 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 alteration 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