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VANCOUVER -- A high percentage of former National Football League players show evidence of having experienced traumatic brain injury, most likely from concussions and near-concussions suffered in playing the violent sport, researchers suggested here.

Of the 40 ex-players who underwent diffusion tensor MRI scans, 17 (43%) were diagnosed with traumatic brain injury, said , head of the Florida Center for Headache and Sports Neurology in Port St. Lucie and a faculty member at Florida State University in Tallahassee.

Those 17 had levels of water movement on MRI that was 2.5 standard deviations below those of healthy people of the same age, which is considered evidence of traumatic brain injury, Conidi reported at the annual meeting of the American Academy of Neurology. The scans measured the amount of damage to the brain's white matter, which connects different brain regions, based on the movement of water molecules in the brain tissue.

"This is one of the largest studies to date in living retired NFL players and one of the first to demonstrate significant objective evidence for traumatic brain injury in these former players," he said in his poster presentation. "The rate of traumatic brain injury was significantly higher in the players than that found in the general population," he said.

"Given the working hypothesis that chronic traumatic encephalopathy results from traumatic brain injury, these results may provide a possible link to the pathological changes being seen," Conidi suggested.

, professor and vice chair of research and chief of neuromuscular medicine at the University of Utah School of Medicine, Salt Lake City, told 番茄社区app, "This study is highly relevant to players in the National Football League from their personal health perspective but I think it has implications for broader public health in terms of sporting settings, youth sports and otherwise and also the larger landscape of brain injury.

"It is important to recognize how chronic traumatic encephalopathy and concussion intersect with the larger issue of neurodegenerative disease and Alzheimer's disease and so forth. It is very important from the public health perspective and also from our larger efforts to understand brain disease."

Conidi's study included seven offensive linemen, of whom two showed abnormal results; seven running backs, three abnormal; 11 defensive linemen, seven abnormal; five wide receivers, three abnormal; six defensive backs, two abnormal; and three linebackers and one quarterback who all tested normal. He noted that 50% of all linemen showed a positive result on the imaging studies, indicating traumatic brain injury among these players.

For the study, Conidi and colleagues conducted thinking and memory tests in the 40 retired players, along with the brain scans. The players were an average age of 36, ranging from 27 to 56. Most had been out of the NFL for less than 5 years. They played an average of 7 years in the NFL, with a range of 2 to 17 years. They reported an average of 8.1 concussions.

Twelve players, or 31%, said they had several sub-concussive hits, those considered below the threshold of a diagnosed concussion.

Conidi said that 12 of the former players – 30% of the sample size – showed evidence on traditional MRI of injury to the brain due to disruption of the nerve axons.

On the tests of thinking skills, about 50% had significant problems on executive function, 45% on learning or memory, 42% on attention and concentration, and 24% on spatial and perceptual function. The more years a player spent in the NFL, the more likely he was to have the signs of traumatic brain injury on the diffusion tensor MRI (P=0.0491), Conidi said.

However, he was unable to establish a relationship between the number of concussions a player had and whether he had traumatic brain injury based on the advanced MRI.

"We found that longer careers placed the athletes at a higher risk of traumatic brain injury," said Conidi. "This research in living players sheds light on the possible pathological changes consistent with chronic traumatic encephalopathy that may be taking place."