Researchers have found that not enough attention has been given to the purposeful use of the head to control the ball and the long-term consequences of repetitive heading.
The literature was reviewed by Dr. Tom Schweizer, director of the Neuroscience Research Program of St. Michael's Hospital.
More than 265 million people play soccer worldwide, including 27 million in North America. Due to the nature of the sport, players are particularly vulnerable to head and neck injuries.
Most are caused by unintentional or unexpected contact, such as when a player collides with teammates, opponents or the playing surface.
There is significant concern in the sporting and medical worlds about the potential long-term cognitive and behavioural consequences for athletes who suffer acute or repeat concussions or multiple "sub-concussive" head impacts-blows to the head not causing symptoms of concussions.
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"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," neuroscientist Dr. Schweizer said.
"Thus, soccer players present a unique opportunity to study whether cumulative sub-concussive impacts affect cognitive functioning, similar to that of concussions," he said.
Studies on the long-term effects of heading found greater memory, planning and perceptual deficits in forwards and defenders, players who execute more headers. One study found professional players reporting the highest prevalence of heading during their careers did poorest in tests of verbal and visual memory as well as attention.
Monica Maher, a co-author and University of Toronto master's degree student in neuroscience, said the researchers wanted to emphasize possible injury prevention methods.
"Use of protective headgear, limiting heading exposure or stressing proper heading technique in younger children and increasing concussion education are all suggestions to perhaps decrease the incidence of head injury and their subsequent effects in the long run," she said.
The study is published in the journal Brain Injury.
