Brain Injury Contact Sports
December 12, 2013

Contact Sports Affect The Brain, Even When There’s No Concussion

[ Watch The Video: Effects Of Head Impacts In College Athletics ]

Brett Smith for - Your Universe Online

Leagues for professional contact sports have been increasingly concerned with the impact of concussions on the long-term mental health of their athletes. However, new research from Indiana University has indicated that concussions may only be part of the story.

According to the researchers’ report in the journal Neurology, a single season of full-contact, college football or hockey at the varsity level can cause changes in the brain's white matter and cognitive abilities even without the athlete being diagnosed with a concussion.

In the study, researchers tracked two groups of athletes over a single season: 80 concussion-free hockey and football players and 79 athletes from non-contact sports such as track, crew and Nordic skiing. The football and hockey players wore helmets equipped with accelerometers, which tracked the number and brutality of impacts to their heads. Players who were diagnosed with a concussion during the season were eliminated from the analysis.

"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," said Dr. Thomas W. McAllister, study author and chair of the IU psychiatry department.

White matter is comprised of axons – long fibers that send signals between neurons. Before and after their season, participants underwent an MRI test known as diffusion tensor imaging, which was used to determine the integrity of the athletes’ white matter. Participants were also administered the California Verbal Learning Test II to determine their capacity for verbal learning and memory.

“There was a group of contact sports athletes who didn't do as well as predicted on tests of learning and memory at the end of the season, and we found that the amount of change in the white matter measures was greater in this group,” McAllister said.

Twenty percent of the contact athletes and 11 percent of the non-contact athletes scored more than 1.5 standard deviations below the forecasted score. McAllister said these results would have been expected in less than seven percent of a normal population. The lower-performing participants also showed more change in the corpus callosum region of the brain than their counterparts who scored as predicted. The corpus callosum is the structure that connects the right and left sides of the brain.

While the study did not find "large-scale, systematic differences" in the brain scans at the end of the season, the authors found this result "somewhat reassuring" and consistent with the fact that thousands of people have played contact sports for many years without developing cognitive disorders.

However, the results do suggest that some athletes may be more susceptible to repeated head impacts that do not involve concussions. "This group of athletes with different susceptibility to repetitive head impacts raises the question of what underlying factors might account for the changes in learning and memory, and whether those effects are long-term or short-lived," McAllister said.

"This study raises the question of whether we should look not only at concussions but also the number of times athletes receive blows to the head and the magnitude of those blows, whether or not they are diagnosed with a concussion," he added.