Soccer players who repeatedly strike the ball with their heads may be causing measurable damage to their brains, even if they never suffer a concussion ...
Statistics offered by the American Assn. of Neurological Surgeons suggest that soccer players, particularly young ones, are much less likely to suffer concussions than other athletes. In 2009, soccer players under the age of 15 suffered 8,392 concussions, according to the group. In contrast, bicyclists in that age group suffered 40,272 concussions; football players, 21,878; and baseball and softball players, 18,246.
However, the JAMA study focused on "sub-concussive" injuries, impacts that were not strong enough to cause a concussion. In selecting their soccer-player subjects, researchers included only men who had never reported suffering a concussion and had never been diagnosed with one by a physician.