Hits to the head change brain's white matter
A study published in the journal Neurology says that repeated blows to the head during a season of contact sports may cause changes in the brain’s white matter and may affect cognitive abilities, even if none of the hits resulted in a concussion.
To conduct their study, researchers from the Indiana School of Medicine and the Geisel School of Medicine at Dartmouth College used a form of magnetic resonance imaging (MRI) called diffusion tensor imaging on varsity football and hockey players and a group non-contact sport athletes following one season of competition. They found significant differences in the white brain matter of the football and hockey players, compared to the white matter of the non-contact sport athletes.
Dr. Thomas W. McAllister, chair of the IU Department of Psychiatry, notes that the number of times the contact sport athletes were hit, along with the magnitude of the hits they sustained, correlated with the changes in the white matter measures. They also found that there was a group of contact sport athletes that didn’t do as well on tests of learning and memory at the end of the season, which also correlated with a greater change in the white matter.
Despite these results, the study did not find “large-scale, systematic differences” in the brain scans at the end of the season, which the authors found consistent with the fact that thousands of individuals have played contact sports for many years without developing progressive neurodegenerative disorders. However, the results do suggest that some athletes may be more susceptible to the effects of repeated head impacts that do not involve concussions, although more research would be necessary to determine how to identify those athletes.