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Many Hits, Rather Than A Big One, Pose Greatest Concussion Risk

High school football players have changes in their brain function long before they have recognizable signs of a concussion, according to a new study.

The more hits a player got, the more brain function changed. The findings support the growing belief that a concussion comes as the result of a succession of insults, not just one bad hit.

"I think what you're seeing here is the sum total of what happens throughout the season," says Eric Nauman, an associate professor of mechanical engineering at Purdue University and lead author of the study.

This researchers followed players on the Jefferson High School football team in Lafayette, Ind., over two seasons. The athletes wore special helmets with sensors that measured the number and severity of head impacts. The researchers also put the players in an MRI scanner to measure their brain activity while the students took a test of thinking and memory.

Then they compared the brain scans with the hits. Those hits weren't rare. Each player logged from 200 to more than 1,800 hits to the head in a single season. Over two seasons, six players had concussions, but 17 others showed brain changes even though they didn't have concussions. There were 21 players in the first season, and 24 in the second, 16 of whom were repeat participants in the study.

Over time, the changes in brain function that showed up in the MRIs correlated to the number and distribution of hits. Mental performance didn't change, but brain activity did.

"The magnitude of changes in the brain were a function of how many hits you took, and where you took them," Nauman told Shots.

Those brain changes may be workarounds, with the brain using other areas to replace those affected by the hits, according to Thomas Talavage, an associate professor of electrical and computer engineering at Purdue University and a co-author of the study. The results haven't been been published yet, but the work has been accepted by the Journal of Biomechanics.

This study raises a lot of questions that it can't answer. It doesn't tell us if these brain changes will improve over time, or if they're the beginnings of permanent brain damage.

The researchers have expanded their work to include two more football teams, and a girls' soccer team. They're also looking for a boys' soccer team, to see if they can test the widely held belief that girls are more vulnerable to concussion.

And they are following the players who took the most hits to see if the brain changes seen are permanent.

Since millions of teenagers play football, soccer, hockey and other sports where hits to the head are common, a clear sense of when those hits start to cause damage would be the start of better ways to prevent and diagnose what has become a major issue in children's health.

Yesterday, Shots reported on a study that found that widely used computerized tests used to establish a baseline of cognitive function for student athletes aren't accurate enough to diagnose concussions, or to determine if a player is safe to return to the action.

Copyright 2012 National Public Radio. To see more, visit http://www.npr.org/.

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