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According to the study, the size, blood flow and connections in their brains were more likely to be affected than those of athletes without prior concussions.Mike Blake/Reuters

Researchers have discovered noticeable changes in the brains of athletes with a history of concussions, months or even years after their last injury. They observed a 10- to 20-per-cent reduction in volume in the frontal lobe as well as 25 to 35 per cent less blood flow to certain areas of the brain, particularly the frontal lobe.

The report, which was published in the Journal of Neurotrauma on Thursday, was performed by researchers at St. Michael's Hospital in Toronto. They tested a broad range of male and female athletes from both high-contact sports, such as football and rugby, and low-contact sports, such as volleyball.

According to Nathan Churchill, the study's lead author and a postdoctoral fellow in St. Michael's Neuroscience Research Program, this is different from most concussion studies, which usually focus on male athletes in "a single high-risk sport like hockey or football."

Using advanced magnetic resonance imaging, the researchers examined the brains of 43 university-level athletes: 21 men and 22 women. Of the 43 participants, 21 had a history of concussions (with a median of two previous injuries) and 22 did not.

According to the study, the size, blood flow and connections in their brains were more likely to be affected than those of athletes without prior concussions.

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The brain shrinkage in the frontal lobe affects the part of the brain responsible for decision-making, problem-solving, impulse control and the ability to speak fluently. Less blood flow can lead to longer recovery times from concussions.

This is important, Churchill said, because many people still think of concussions as "a short-term brain change, where you experience symptoms that last about a week and then you recover … at which point you're effectively back to normal."

Additionally, researchers saw a change in the structure of the brain's white matter – the fibre tracts connecting different areas of the brain – for those who had previous cases of concussions.

While there has been evidence of impaired impulse control and problem-solving in older athletes who experience changes to their frontal lobe, this research illuminates the fact that young athletes with fewer head injuries may also be at risk.

The study is just "laying the groundwork," said Churchill, and further research into low-contact sports is required.

Churchill would also like to monitor athletes' brains at multiple points throughout their careers, to investigate the changes at different times after an injury. This research has just shown that "there actually is something worth chasing," he said.

"This is really just a snapshot of what's going on in the brain at this point in time. And now that we've really shown that there's something there, we're actually interested in moving on and looking at multiple time points to see how does this evolve: Does it stay the same? Does it change? And do people show different symptoms or different outcomes over time as well?" he said. "Now, there's a whole pile of questions raised that we'd like to follow up with."

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Dr. Tom Schweizer, head of the Neuroscience Research Program and co-author of the paper, emphasized that quitting sports is not the answer, as "the health benefits of sport participation still outweigh the risk of concussion."

He believes that these findings can "help to guide concussion management, and to minimize any future risk to athletes."

Churchill hopes that this study will persuade people to take concussions seriously, even if they are playing a low-impact sport.

He also suggested that those with repeated concussions might "have to be managed differently, no matter what sport they're playing."

Schweizer added: "The more we know about concussions, the better we can reduce these risks."

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