Dr. Maryse Lassonde, a neuropsychologist and the scientific director of the Quebec Nature and Technologies Granting Agency and a consultant with the Montreal Canadiens professional hockey team, treated players with concussions for 15 years.
She simultaneously undertook research into the effects of concussions on children and young athletes as well as older athletes.
"Even when you are symptom-free, your brain might still not be back to normal," Lassonde said in a statement.
Lassonde had athletes perform specific visual and auditory tasks and also mapped their brains with the help of electroencephalography, the recording of electrical activity used to diagnose brain disorders; magnetic resonance imaging; in addition to testing brain chemistry.
She demonstrated brain waves remain abnormal in young athletes for two years following a concussion, and atrophy occurred in the motor pathways of the brain following a hit.
By studying older athletes who suffered their last concussion 30 years earlier, and comparing them to healthy peers who had not experienced concussions, Lassonde discovered those who had suffered a head trauma had memory and attention deficits and motor problems similar to the early symptoms of Parkinson's disease.
Further testing of these older athletes turned up a thinning of the cortex in the same regions of the brain that Alzheimer's disease usually affects, Lassonde said.
The findings, published in the journals Brain and Cerebral Cortex, have implications for the regulation of amateur and professional sports.
Lassonde presented the findings at the annual meeting. American Association for the Advancement of Science in Boston.
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