Soccer players who hit the ball with their head a lot don’t score as well on a memory test as players who head the ball less often, a new study finds. Frequent headers are also associated with abnormalities in the white matter of the brain, researchers report June 11 in Radiology.
“These changes are subtle,” says Inga Koerte, a radiologist at Harvard Medical School and Brigham and Women’s Hospital in Boston. “But you don’t need a concussive trauma to get changes in the microstructure of your brain.”
While soccer players can get concussions from colliding with goal posts, the ground or each other, concussions are uncommon from heading the ball, even though it can move at 80 kilometers per hour, says coauthor Michael Lipton, a neuroradiologist at the Albert Einstein College of Medicine in New York City.
He and his colleagues took magnetic resonance imaging scans of 28 men and nine women who played amateur soccer. The players, with an average age of 31, tallied up their games and practice sessions in the previous year and estimated how many headers they had done in each. Most players headed the ball hundreds of times; some hit thousands of headers.
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The MRIs revealed brain abnormalities in some players, mainly in the white matter of three regions of the brain. White matter coats nerve fibers, and bundles of fibers cross and converge in the three regions. But the areas aren’t associated with a single function, Lipton says. Attention, memory, sensory inputs and visual and spatial functions could all be processed there.
Players who headed balls the most showed more abnormalities than those who headed fewer. For one brain region, 850 headers represented a threshold: Players above that mark clearly had more abnormalities than players below it. For the other brain regions, thresholds were about 1,300 and 1,550 headers.
On a standard memory test, the nine players with the highest header count scored worse on average than the nine who had the fewest. The researchers estimated that the threshold for memory loss would be 1,800 headers.
The regions with white matter abnormalities sit toward the back of the head, opposite the typical point of impact of a header. Lipton says brain “recoil” might explain the location. “When there is a head impact, the brain sloshes back and forth inside the head,” he says. On a frontal impact, he says, the brain presses against the front of the skull momentarily and then slams into the back of the skull.
In 2012, Koerte and her colleagues found that soccer players had more white matter abnormalities than swimmers. That report, in JAMA, included only players who had never had a concussion. Lipton’s team found no difference in concussion history when players were grouped by number of headers.