Regularly heading a soccer ball -- even just a few times a day -- can lead to brain injury, an American study said Tuesday.
Researchers used an advanced MRI-based imaging technique to scan the brains of 38 amateur soccer players then compared the images to the number of times they headed the ball during the past year.
Players who frequently headed the ball showed brain injuries similar to those seen in patients with concussions, with researchers from New York's Albert Einstein College of Medicine and Montefiore Medical Center reporting "significant injury" in those players who exceeded 1,000 to 1,500 headers per year.
"While heading a ball 1,000 or 1,500 times a year may seem high to those who don't participate in the sport, it only amounts to a few times a day for a regular player," lead author Michael Lipton said.
"Heading a soccer ball is not an impact of a magnitude that will lacerate nerve fibers in the brain," he added. "But repetitive heading may set off a cascade of responses that can lead to degeneration of brain cells."
Researchers identified five areas of the brain -- responsible for attention, memory and visual functions -- that were affected by heading, according to results announced at the annual meeting of the Radiological Society of North America, in Chicago.
In a related study, researchers found that players who headed a ball most frequently performed worse on tests of verbal memory and psychomotor speed, a measure of hand-eye coordination.
"These two studies present compelling evidence that brain injury and cognitive impairment can result from heading a soccer ball with high frequency," Lipton said.