Worse cognitive function in soccer players stems mainly from frequent ball heading rather than unintentional head impacts due to collisions, researchers at Albert Einstein College of Medicine have found. The findings suggest that efforts to reduce long-term brain injuries may be focusing too narrowly on preventing accidental head collisions.
“Unintentional head impacts are generally considered the most common cause of diagnosed concussions in soccer, so it’s understandable that current prevention efforts aim at minimising those collisions,” said study leader, Dr Michael Lipton, professor of radiology and of psychiatry and behavioural sciences at Einstein and medical director of MRI Services at Montefiore. “But intentional head impacts – that is, soccer ball heading – are not benign. We showed in a previous study that frequent heading is an underappreciated cause of concussion symptoms. And now we’ve found that heading appears to alter cognitive function as well, at least temporarily.”
While heading has previously been associated with transient cognitive problems, the Einstein study is the first to compare the cognitive effects of heading to unintentional head impacts such as collisions. Three hundred and eight amateur soccer players in New York City filled out questionnaires detailing their recent (previous two weeks) soccer activity, including heading and unintentional head impacts. Participants also completed neuropsychological tests of verbal learning, verbal memory, psychomotor speed, attention and working memory. The players ranged in age from 18 to 55, and 78% were male.
Players headed soccer balls an average of 45 times during the two weeks covered by the questionnaire. During that time, about one-third of the players suffered at least one unintentional head impact (kicks to the head or head-to head, head-to-ground, or head-to-goalpost collisions).
Players who reported the most headings had the poorest performance on psychomotor speed and attention tasks, which are areas of functioning known to be affected by brain injury. Heading frequency also correlated with poorer performance on the working memory task, although the association was of borderline significance. In contrast, unintentional head impacts were not related to any aspect of cognitive performance.
The changes in cognitive function did not cause overt clinical impairment, the Einstein team reported. “However, we’re concerned that subtle, even transient reductions in neuropsychological function from heading could translate to microstructural changes in the brain that then lead to persistently impaired function. We need a much longer-term follow-up study of more soccer players to fully address this question,” said Lipton.
In the meantime, soccer players should consider reducing heading during practice and soccer games, Lipton advises. “Heading is a potential cause of brain injury,” he says, “and since it’s under control of the player, its consequences can be prevented.”
The study was funded by grants from the National Institutes of Health and the Dana Foundation David Mahoney Neuroimaging Programme.
Anthony Kontos, research director for the UPMC Sports Medicine Concussion Programme at the University of Pittsburgh, who wasn’t involved in the study, noted that while the study involved a lot of players, it’s possible participants may have overstated the number of times they headed the ball.
“As a researcher who has published in this area and as a long-time soccer player who played in college and continues to play as an adult, I know first-hand that most players do not accurately recall heading exposure. Most likely, players over estimated their exposure to heading and lifetime head injuries,” Kontos said.
Lipton said more research is needed. “The only way to really understand this is to follow people over a much longer time frame because the effects were small, but the question is how do they build up over time?”
Objective: Compared to heading, unintentional head impacts (e.g., elbow to head, head to head, head to goalpost) in soccer are more strongly related to risk of moderate to very severe Central Nervous System (CNS) symptoms. But, most head impacts associated with CNS symptoms that occur in soccer are mild and are more strongly related to heading. We tested for a differential relation of heading and unintentional head impacts with neuropsychological (NP) test performance.
Method: Active adult amateur soccer players were recruited in New York City and the surrounding areas for this repeated measures longitudinal study of individuals who were enrolled if they had 5+ years of soccer play and were active playing soccer 6+ months/year. All participants completed a baseline validated questionnaire (“HeadCount-2w”), reporting 2-week recall of soccer activity, heading and unintentional head impacts. In addition, participants also completed NP tests of verbal learning, verbal memory, psychomotor speed, attention, and working memory. Most participants also completed one or more identical follow-up protocols (i.e., HeadCount-2w and NP tests) at 3- to 6-month intervals over a 2-year period. Repeated measures General Estimating Equations (GEE) linear models were used to determine if variation in NP tests at each visit was related to variation in either heading or unintentional head impacts in the 2-week period before testing.
Results: 308 players (78% male) completed 741 HeadCount-2w. Mean (median) heading/2-weeks was 50 (17) for men and 26 (7) for women. Heading was significantly associated with poorer performance on psychomotor speed (p < 0.001) and attention (p = 0.02) tasks and was borderline significant with poorer performance on the working memory (p = 0.06) task. Unintentional head impacts were not significantly associated with any NP test. Results did not differ after excluding 22 HeadCount-2w with reported concussive or borderline concussive symptoms.
Conclusion: Poorer NP test performance was consistently related to frequent heading during soccer practice and competition in the 2 weeks before testing. In contrast, unintentional head impacts incurred during soccer were not related to cognitive performance.
Walter F Stewart, Namhee Kim, Chloe Ifrah, Martin Sliwinski, Molly E Zimmerman, Mimi Kim, Richard B Lipton, Michael L Lipton