Matser EJT, Kessels AG, Lezak MD, Jordan BD, Troost J. Neuropsychological Impairment in Amateur Soccer Players. JAMA. 1999;282(10):971–973. doi:10.1001/jama.282.10.971
Author Affiliations: Department of Neuropsychology and Sports Neurology, St Anna Hospital, Geldrop, the Netherlands (Dr Matser); Department of Anatomy, Faculty of Medicine and Health Sciences, Erasmus University, Rotterdam, the Netherlands (Dr Matser); Research Unit Patient Care (Dr Kessels) and Department of Neurology (Dr Troost), University Hospital of Maastricht, Maastricht, the Netherlands; Department of Neurology, Oregon Health Sciences University, Portland (Dr Lezak); and Traumatic Brain Injury Program, Burke Rehabilitation Hospital, White Plains, NY (Dr Jordan).
Context Soccer players incur concussions during matches and training sessions,
as well as numerous subconcussive blows to the head from impacts with the
soccer ball (headers). The combination of soccer-related
concussions and the number of headers may be a risk for chronic traumatic
brain injury (CTBI).
Objective To determine whether amateur soccer players have evidence of CTBI.
Design, Setting, and Participants Cross-sectional study of 33 amateur soccer players and 27 amateur athletes
involved in swimming and track (controls) in the Netherlands who underwent
interviews and neuropsychological testing.
Main Outcome Measures Performance of soccer players vs controls on 16 neuropsychological tests
having 27 outcomes.
Results Compared with control athletes, amateur soccer players exhibited impaired
performance on tests of planning (39% vs 13%; P=.001)
and memory (27% vs 7%; P=.004). Among soccer players,
9 (27%) had incurred 1 soccer-related concussion and 7 (23%) had had 2 to
5 concussions during their career. The number of concussions incurred in soccer
was inversely related to the neuropsychological performance on 6 of the neuropsychological
Conclusions Our results indicate that participation in amateur soccer in general
and concussion specifically is associated with impaired performance in memory
and planning functions. Due to the worldwide popularity of soccer, these observations
may have important public health implications.
Chronic traumatic brain injury (CTBI) is the cumulative long-term neurologic
consequence of repetitive concussive and subconcussive blows to the head,
and has been described primarily among professional boxers.1- 4
Evidence suggests that CTBI also may be associated with professional soccer.5,6 Neuropsychological impairment and neurological
abnormalities have been observed in retired amateur and active professional
soccer players.7- 11
A survey of active soccer players reported that neurological symptoms correlated
with reported history of acute head injury received during play.12
To date, only 1 preliminary investigation evaluated neuropsychological functioning
in nonprofessional high school soccer players.13
The current investigation was undertaken to determine if neuropsychological
dysfunction occurs in amateur soccer players.
Between September 1997 and May 1998, athletes from 3 complete teams
of 3 different regional-league amateur soccer clubs (n=33) were compared with
27 control athletes. The control athletes were middle-distance runners (2
complete premier-league track teams) and middle-distance swimmers (1 complete
premier-league team) from the same region as the soccer clubs. All participants
completed an interview that inquired about age, education, lifetime number
of general anesthesias, occupational history, learning disorders, lifetime
number of concussions (sports- and nonsports-related), alcohol intake, drug
use, and medical conditions that might affect cognitive functioning. The primary
physicians for all participants were interviewed regarding the number of concussions
the athletes had incurred and medical conditions that might interfere with
cognitive functioning. All participants in this study were native to the Netherlands
and educated in the Dutch educational system. Athletes also were excluded
for history of drug use, learning disorders, epilepsy, and other medical conditions
that might affect cognitive functioning. Education was scored on a 7-point
scale and because all participants completed their secondary school education,
only level 3 (technical and vocational training for ages 12-16 years) to level
7 (academic) were used. This study was approved by the St Anna Hospital Medical
Ethical Committee and oral informed consent was obtained from all participants.
Each participant was interviewed by a neuropsychologist and received
neuropsychological tests administered by an experienced psychometrician. All
tests were administered according to standardized procedures. The test data
were scored by a neuropsychologist who was blinded to the status of the participants.
The neuropsychological tests included the Raven Progressive Matrices,14 Wisconsin Card Sorting Task,15
Paced Auditory Serial Addition Task,16 Digit
Symbol Modalities Test,17 Trail-Making tests
A and B,18 Stroop Test,19
Bourdon-Wiersma Test,20 Wechsler Memory Scale
(Associate Learning, Logical Memory, and Visual Reproduction subtests),21 Complex Figure Test,22
15-Word Learning Test,23 Benton Facial Recognition
Test,24 Figure Detection Test,25
Verbal Fluency Test,25 and Puncture Test.26
The means of the neuropsychological test scores were compared using
the t test, with 1-tailed P
values. The differences, their confidence intervals, and 1-tailed P values were determined with a linear regression analysis adjusting
for level of education, alcohol intake, number of general anesthesias, and
number of concussions not due to soccer play.
Multiple end point testing was controlled for by clustering the 27 test
scores into 8 cognitive functions as described by Lezak.27
For each cluster, a global null hypothesis stating that all differences of
the included test scores are 0 was tested using the ordinary least squares
(OLS) test.28 For the 8 resulting 1-tailed P values, a Bonferroni correction for the significance
level was applied. In addition, the means of the neurocognitive test scores
among the soccer players were analyzed. Soccer players with and without soccer-related
concussions were compared using the t test.
Soccer players were similar to controls in age, education level, nonsoccer-related
concussions, and number of times they had received general anesthesia (Table 1). The soccer players exhibited
a higher frequency of alcohol intake per month compared with controls.
The average duration of an amateur career was 17 years. Thirty-three
percent played 5 to 15 years and 67% played more than 16 years. The average
time spent in training practices was 3.6 h/wk and the median of the number
of matches played annually was 36 (range, 20-70). The median number of balls
headed in a match was 8.5 (range, 0-20). Nine players (27%) incurred 1 soccer-related
concussion; 7 players (23%) reported 2 to 5 concussions in a career.
Amateur soccer players exhibited impairment in planning (OLS P=.001) and memory (OLS P=.004) (Table 2). These scores remained statistically
significant after Bonferroni correction. After adjusting for concussions unrelated
to soccer, alcohol intake, level of education, and number of general anesthesias,
soccer players performed significantly poorer (1-tailed P<.05) on the Complex Figure Test (Immediate Recall [P=.03]); Digit Span Test (Forward [P=.01]
and Backward [P=.01]); and Logical Memory (P=.01), Visual Reproduction (P=.04),
and Associate Learning (P=.03) subtests of the Wechsler
Concussions incurred in soccer were inversely correlated with performances
on the Digit Span Test (Forward) (P=.004), Facial
Recognition Task (P=.001), Complex Figure Test (Immediate
Recall) (P=.04), Complex Figure Test (Delayed Recall)
(P=.03), Digit Symbol Modalities Test (P=.03), and Logical Memory subtest of the Wechsler Memory Scale (P=.006).
These findings suggest that participation in amateur soccer may be associated
with mild CTBI, as evidenced by impairment in cognitive functioning based
on tests of memory and planning. Concussions incurred in amateur soccer may
play a fundamental role in the development of cognitive impairment observed
in these players.
As reported in our previous study of professional soccer players,11 amateur soccer appears to be associated with impairments
in planning and memory functions. The Complex Figure Test Immediate Recall
(memory) and the Wisconsin Card Sorting Task (planning) were sensitive in
detecting symptoms of neurocognitive impairment in amateur soccer players.
According to standards used in clinical practice,27
7% of controls and 27% of amateur soccer players showed moderately to severely
impaired scores on the memory test and 13% of controls and 39% of amateur
soccer players showed moderately to severely impaired scores on the planning
test. The neurological effects of amateur soccer appear to be related to soccer-related
concussions caused by contact trauma. Most of the memory tests that showed
a significant difference between the soccer players and the controls were
inversely related with concussions incurred in soccer in the intragroup analysis.
In conclusion, participation in amateur soccer is associated with decreased
performance on tests of memory and planning. Although cognitive impairment
appears to be mild, it presents a medical and public health concern, with
200 million Federation International Football Association–registered
soccer players worldwide. Methods for surveillance and prevention should be
developed and adopted to maximize safety.