Washington: Repeated blows to the head during a season of contact sports could cause brain changes and affect cognitive abilities even if none of the impacts have resulted in a concussion.
Thomas W. McAllister, M.D., chair of the Indiana University Department of Psychiatry, said that the contact sports and noncontact-sports groups differed, and the number of times the contact sports participants were hit, and the magnitude of the hits they sustained, were correlated with changes in the white matter measures.
Two groups of Dartmouth athletes were studied: 80 football and ice hockey players in the contact sports group, and 79 athletes drawn from such noncontact sports as track, crew and Nordic skiing.
The football and hockey players wore helmets equipped with accelerometers, which enabled the researchers to compile the number and severity of impacts to their heads.
The athletes were administered a form of MRI test known as diffusion tensor imaging, which is used to measure the integrity of the white matter. They were also given the California Verbal Learning Test II, a measure of verbal learning and memory.
The study did not find "large-scale, systematic differences" in the brain scan measures at the end of the season, which the authors found "somewhat reassuring" and 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 repeated head impacts that do not involve concussions, although much more research would be necessary to determine how to identify those athletes.
The study has been published in the journal Neurology.