Coaches value players who have their head in the game, but a new study finds that may not be the healthiest thing for soccer players. Those who head the ball most frequently, the study showed, had damage in brain areas similar to that seen in people with concussion.
The brain changes were found in players who headed the ball 1,000 to 1,500 times a year — which amounts to a few times a day — but not in those who did so less frequently. Reporting the findings at the Radiological Society of North America’s annual meeting in Chicago this week, the study’s author said the effects of heading may be cumulative — appearing not after the occasional header, but building up over time in players who frequently use their heads to play.
“I’m not advocating banning heading, but there may be a threshold level, which we defined, that indicates a safe range of heading,” said author Dr. Michael Lipton, associate director of the Gruss Magnetic Resonance Research Center at the Albert Einstein College of Medicine in New York City, in a statement.
The researchers used a type of brain scan known as diffusion tensor imaging to examine the brain tissue of 38 amateur adult soccer players in New York City, who said they had been playing since childhood. Players reported heading the ball more than 400 times a year on average. Those in the top 25% of heading frequency had an average 1,320 headers in a year, and these players were most likely to show injury in regions of the brain that play a role in cognitive functions, including attention, memory, planning, organizing, physical mobility and high-level visual functions.
“These are changes in the brain that are similar to those we see with a concussion or TBI,” said Lipton. In previous research, these players also showed lower scores on tests of memory and reaction time.
The evidence linking brain injury and heading has been inconsistent so far. For its part, the American Academy of Pediatrics says there isn’t sufficient data to recommend that young players abstain from heading, but does suggest that players minimize contact between head and ball.
The new study is small and not peer-reviewed, so it must be considered preliminary. But the author said it was a compelling reason to pursue further study; other experts agreed that more study was necessary to determine what the implications might be for soccer players, especially younger ones who may be more vulnerable to brain injury and for those who practice daily, doing frequent heading drills.
More than 250 million people play soccer regularly, according to FIFA, the sport’s international governing body. In the U.S., at least 18 million people play soccer, 78% of them under age 18.
Meredith Melnick is a reporter at TIME. Find her on Twitter at @MeredithCM. You can also continue the discussion on TIME’s Facebook page and on Twitter at @TIME.