In a paper published Monday, Toronto researchers warn that not enough attention has been paid to the impact of repetitive heading in soccer.
A literature review published in the journal Brain Injury by Dr. Tom Schweizer, director of the neuroscience research program at Toronto's St. Michael's Hospital, calls for more research to be done specifically on a unique aspect of soccer – purposely using one's head to control the ball – and the long-term consequences of repetitive heading.
"The practice of heading, which might occur thousands of times over a player's career, carries unknown risks, but may uniquely contribute to cognitive decline or impairment in the short or long term," Schweizer said. "Thus, soccer players present a unique opportunity to study whether cumulative subconcussive impacts affect cognitive functioning, similar to that of concussions."
Schweizer did a comprehensive review of the current published works on brain injuries in the world's most popular and fastest-growing sport, along with co-author Monica Maher, a University of Toronto master's degree student in neuroscience and former goaltender with its varsity soccer team. Maher said in their review of research published up to May, 2012, they found just 49 papers specifically focused on brain injuries in soccer, which paled in comparison to the amount of research that has focused on concussions in football and hockey.
"There needs to be more standardized ways of measuring the head exposure in soccer," said Maher. "Some studies had players estimate the number of times they headed the ball, while others used direct observation. And there were a huge number of different neuropsychological tests employed by the different studies, so using something common, like the ImPACT [immediate postconcussion assessment and cognitive testing] test or the Automated Neuropsychological Assessment Metrics would allow for the studies and the conclusions to be better compared."
Examining research papers that studied the incidence of concussion in soccer, they found that concussions accounted for 5.8 per cent to 8.6 per cent of total injuries sustained during games. One study found concussions suffered during soccer accounted for 15 per cent of the total number of concussions in all sports. In particular, girls' soccer made up 8.2 per cent of sports-related concussions, the second highest sport after football. Their review also found that defenders and goalkeepers are at greatest risk for suffering a concussion, but that it decreased for the keepers as they got older and were more aware of their relation to the goalposts.
Studies specifically on the long-term effects of heading found greater memory, planning and perceptual deficits in forwards and defenders, players who execute more headers.
Maher suggested wider populations of soccer players need to be studied. Also, she said very little research has been done on soccer players' brains using neuroimaging technology, yet it has been more frequently used in studies on hockey and football players. The few studies that did use advanced imaging techniques found physical changes to the brains in players who had concussions.
Maher and Schweizer would like to see further study done on brain injuries in soccer, especially on the type of repetitive blows to the head not causing symptoms of concussions. They would also like spark conversation about the possibility of protective headgear and padded goalposts in youth soccer. They point to the need for teaching proper heading technique to young players and suggest limiting the number of times a child heads the ball in training.
"We're not at all advocating people stop playing soccer," said Maher. "We're calling for more comprehensive research to be done on wider populations of soccer players and with standardized methods."