STUDIES OF SOCCER AND FOOTBALL PLAYERS
The laboratory research previously discussed suggests that the concussions experienced by soccer or football players might be detrimental to the brain. To see if that suggestion holds true on the soccer or football field, a number of experts presented their findings on these athletes.
These experts found hampered brain functioning for a short period following a concussion, and long-lasting brain damage often ensuing in athletes that suffer a second concussion before fully recovering from a first. But many studies presented found no evidence that soccer playing appeared to impair brain functions in the long-term, even when players experienced concussions or did frequent heading during games or practice.
Dr. Echemendia used a broad battery of neuropsychology tests to study brain function in college athletes, but found no significant differences in the mental performance of freshmen soccer players versus freshmen swimmers or other athletes in noncontact sports not likely to foster head injuries. Epidemiologist Dr. Linda Cowan added that since most of these soccer athletes had been playing soccer at least a decade before Dr. Echemendia tested them, if there were long-term neuropsychological consequences from playing soccer, they most likely would have been detected in his study.
Dr. Guskiewicz conducted a similar study on college freshmen athletes and found no significant differences between soccer players and non-soccer athletes or nonathletic students in terms of Scholastic Aptitude Test (SAT) scores or neuropsychological test results. The soccer players had played soccer for an average of 15 seasons and were more likely to have experienced one or more concussions compared to the other groups. But at the same time, the number of previous concussions among the soccer players was not significantly related to either their SAT or neuropsychological test scores.
Dr. Kirkendall also described a study done by California researchers that found no differences in neuropsychological function between soccer players and track athletes.
To test whether heading causes deficits in mental functions, Dr. Echemendia conducted a battery of neuropsychology tests on college soccer players when they exercised for twenty minutes, versus when they spent an equal amount of time heading the ball. He found no differences in test results between the two, although the players that headed the ball more had more headaches.
Dr. Echemendia also assessed whether college soccer players who frequently head the ball do worse on neuropsychology tests versus those who rarely head the ball. He found no differences between the two groups after they played nearly ten games. (To avoid confusing the effects of concussions on the results he only compared players who hadn’t experienced any concussions during the study.)
In contrast to these findings, neuropsychologist Dr. Muriel Lezak presented findings of three other studies conducted on Dutch athletes that suggest the heading and concussions experienced by soccer players can cause long-term brain function deficits.
The Dutch studies found that, compared to swimmers or track athletes, soccer players scored
significantly lower on tests that measured visual and verbal memory, visual analysis and planning, and mental flexibility. Those test results suggest that these players would be slower at learning and remembering new material that they hear or see, Dr. Lezak said. The study results were similar for comparisons of amateur as well as professional athletes.
While several studies of European soccer players raise concerns about the possibility, most studies of American soccer players allay those concerns.
The studies of professional soccer players in the Netherlands also found that soccer players who did more heading or experienced more concussions scored lower on visual and verbal memory tests, visual analysis planning and tasks requiring focused attention and visual scanning. But there were differences between the two groups. Players who were frequent headers displayed decrements in both verbal and visual learning and visuographic tracking speed when compared with those who had been concussed more, although the latter group had decrements in visuospatial organization and fine visual discrimination, she said. The differences between these groups reflect the areas of the brain likely to be affected by concussions versus heading, she suggested.
WHAT IS NEUROPSYCHOLOGY?
Neuropsychology is the study of human behavior as it relates to normal and abnormal functioning of the brain. Clinical neuropsychologists apply scientific knowledge about the relationship between brain function and mental performance to help answer diagnostic questions about medical patients.
Neuropsychological assessment uses behavioral methods such as interviews, observations, paper-pencil and computerized tests, or other specialized procedures to evaluate changes in mental abilities and personality as a result of neurologic disorder. A key component of neuropsychological assessment is the administration of tests of mental abilities such as memory and reasoning. An evaluation may also involve assessment of change in personality, behavioral, and emotional functioning that might reflect neurologic dysfunction or psychological reaction to disease.
People may be referred for neuropsychological assessment after a concussion or other head injury to assess whether certain types of brain functions have been affected. Neuropsychological testing provides a wealth of practical information useful to both the physician and the patient. Test results can help clarify the nature of cognitive difficulties and support the formulation of plans for treatment, rehabilitation, and psychological adjustment.
But some of the experts at the workshop questioned the validity of these findings of adverse effects of heading, and soccer playing in general. Dr. Kirkendall pointed out that the results from studies of European soccer players may not be comparable to those of players in this country, because the Europeans generally use balls that are more highly inflated and thus have more impact when they strike the head. “The alarming numbers we saw from some of the European studies may not translate to the population here,” agreed Dr. Guskiewicz. Dr. Kirkendall added that findings in professional soccer players, who are high-caliber, aggressive athletes may not be applicable to middle or high school soccer players.
To date there has been no published study that has provided direct evidence that the practice of heading a soccer ball causes long-term deficits in mental functions. While several studies of European soccer players raise concerns about the possibility, most studies of American soccer players allay those concerns. However, few of those studies were designed to directly study the effects of heading the ball, because they were cross-sectional studies, based on players’ condition at only one point in time with no information about their condition before they became elite soccer players. Dr. Kirkendall described one prospective study in which the consequences of heading could be directly assessed by comparing players before and after heading the ball. That study, by Dr. Margot Putukian, showed no differences on neuropsychological tests before and after heading, although that was a short-term study not designed to detect long-term effects. In 2002, Dr. Kirkendall and his colleagues will launch a 5-year longitudinal study of soccer players on the United States National Youth teams. That study should be able to settle the question as to whether heading the ball is followed by brain injury, at least among players at this level. (At ages 16-21, these are already elite soccer players competing at a much higher level than children who play on recreational teams.)
Summing up the human findings presented, Dr. Echemendia said, “The data show that, all
in all, playing soccer is not dangerous to your brain, at least based on what we know at this point in time. The data also show that heading, in and of itself, does not seem to be a significant problem, at least in those people that it has been studied. However, heading does put the player at risk in the sense of having their head make contact with a number of different objects—somebody else’s foot or head, or a goal post—so we need to put that caveat in there.”
Thus far no published study has provided direct evidence that the practice of heading a soccer ball causes long-term deficits in mental functions. Nor has any study been published that proves heading has no long-term effects. To date, the best evidence is suggestive. The long-term effects of repetitive heading will not be known until the completion of well-designed, long-term studies that evaluate players before and for years after they frequently head soccer balls. The tables on the following page summarize studies presented at the workshop, and are not a comprehensive summary of all studies relevant to head injury in soccer.
Helmets Are Not Designed to Prevent Concussion
The notion that soccer might put youths at risk for brain injury has circulated in the popular media and that has led some to suggest that soccer players wear protective headgear. But as bioengineer Dr. Joseph “Trey” Crisco pointed out, there are a number of concerns with this suggestion. For one, no protective headgear currently on the market is designed to protect against concussion. Today’s helmets are designed to meet standards for reducing the risk of serious and fatal brain injury and these standards are limited to reducing injury caused by a linear acceleration, or a ‘straight on’ blow to the head. But a blow that causes concussion typically includes rotational acceleration, in which the brain gets twisted. Current helmets and standards are not designed to take this type of blow into account.
Dr. Crisco, who is the Director of Research for the National Operating Committee on Standards for Athletic Equipment, noted that football and other protective helmets were developed based on data from experiments in which high impacts were applied to the heads of cadavers from elderly men. He questioned the relevancy of that data set to the youths and females that play soccer and suggested that helmets developed from this data may not be as protective against brain injury in youths and women as they are in men.
We talk to trainers, to equipment managers, and they are very surprised when I say that no helmet is designed to prevent concussions.”
“The concern that I have from an engineering perspective is that if you place headgear on children [who play soccer] there is going to be a limited understanding,” he said. “We talk to trainers, to equipment managers, and they are very surprised when I say that no helmet is designed to prevent concussions.” Most parents, players, and coaches are going to assume it will prevent concussions when it is not designed to do so, he noted. “And then we have the Superman phenomenon,” he added. “You place equipment on players and they believe they are less at risk so they may place themselves more at risk in getting involved in heading or head-to-head player contact than they normally would.”
Dr. Crisco suggested that it might be more cost effective to develop standards for soccer balls so that they are not likely to cause brain injury, than to do so for protective soccer headgear. The structure, weight, and other material properties of soccer balls all influence the amount of impact they can have on the head, he noted. The research needed to develop standards for soccer balls would be easier and less expensive to conduct than the research needed for soccer headgear, according to Dr. Crisco.
BOX 1A. STUDIES THAT SUGGEST HEADING CAUSES BRAIN INJURY