Adult soccer players who regularly use their heads to hit balls are three times more likely to show concussion symptoms than players who don't head the ball often, a U.S. study said Wednesday.
Published in Neurology, the medical journal of the American Academy of Neurology, the findings were based on more than 200 adult amateur soccer players in the New York City area.
"These results show that heading the ball is indeed related to concussion symptoms, which is contrary to a recent study that suggested that collisions were responsible for most concussions," said study author Michael Lipton of Albert Einstein College of Medicine in New York.
"Many players who head the ball frequently are experiencing classic concussion symptoms such as headache, confusion, and dizziness during games and practice, even though they are not actually diagnosed with concussion."
Players completed an online questionnaire about how often they played soccer during the previous two weeks.
They were also asked how many times they headed the ball, and how many times they had unintentional head impacts, such as colliding with another player.
Players were also asked how often they experienced any symptoms from the head impacts.
The participants were divided into four groups, with those in the top sector saying they headed the ball an average of 125 times in two weeks, and members of the bottom group saying they headed the ball about four times in two weeks.
"Those in the group with the most headers were three times more likely to have symptoms than those who headed the ball the least," the study said.
Symptoms ranged from moderate pain and some dizziness to feeling dazed, stopping play, needing medical attention and even losing consciousness.
Some 20 percent of participants reported experiencing moderate to very severe concussion symptoms.
Those symptoms "were more strongly connected with unintentional head impacts," such as colliding with a player or goal post, the study said, adding that "heading was shown to be an independent risk factor for concussion symptoms."
Of the 222 players who completed questionnaires, 79 percent were men.
Researchers cautioned that the study, based on self-reported injuries and symptoms, could contain errors of recollection.
The survey did not include professional players, teenagers or children.
"The findings raise concerns about the long-term effects from heading the ball," Lipton said, adding that "more research is needed."
