Footballers may in future have to wear crash helmets to protect their brains when heading the ball, research suggests.
The idea is one solution put forward by experts to the problem of concussion on the soccer field.
Another is a possible restriction on "headers" in the rules of the game.
Scientists in Canada warned about the dangers of head injury in football after reviewing evidence from a number of research papers.
They found that concussion accounted for up to 8.6% of all the injuries suffered during soccer matches.
In more than 40% of cases the injury was caused by contact by an elbow, arm or hand to the head.
But forwards and defenders were said to be at special risk from heading.
Studies of the long-term effects of heading the ball found a greater impact on memory and thinking ability in these players, both of whom traditionally deliver more headers.
"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," said lead scientist Dr Tom Schweizer, from St Michael's Hospital, Toronto.
"Thus, soccer players present a unique opportunity to study whether cumulative sub-concussive impacts affect cognitive functioning, similar to that of concussions."
The research, published in the journal Brain Injury, included the results of one study showing that almost 60% of soccer concussions occurred during a "heading duel".
Professional players reporting the highest rates of heading during their careers performed the most poorly in tests of verbal and visual memory, as well as attention.
Co-author Monica Maher, a neuroscientist from the University of Toronto, highlighted the importance given to considering ways to reduce the injuries - including helmets.
"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.