Abstract
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. 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. 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. 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.
Highlights
More than 1 in 20 humans currently play soccer, the only sport where athletes deliberately engage in repeated head impacts [1, 2]
We found that among active adult amateur players, central nervous system (CNS) symptoms were reported to occur in 74% of 2-week recall periods [28] and that the 2-week recall of unintentional head impacts was more strongly related to moderate to very severe CNS symptoms than was heading [28], a finding that is consistent with reported causes of concussion in soccer [1, 28]
We used data across 741 visits from 308 soccer players to determine if variation in NP test performance was explained by variation in either heading or unintentional head impacts reported for the preceding 2 weeks
Summary
More than 1 in 20 humans currently play soccer, the only sport where athletes deliberately engage in repeated head impacts [1, 2]. Growing evidence indicates that soccer is associated with risk of persistent central nervous system (CNS) impairment and structural changes [3,4,5,6,7,8,9,10]. These long-term effects may be mediated by short-term effects of soccer [9,10,11,12]. Fewer studies have examined the short-term effects of soccer activity on CNS function [5, 10, 27]
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