Nearly half of retired National Football League players may suffer from traumatic brain injuries, according to results of a diffusion tensor imaging study set to be presented next week at the annual meeting of the American Academy of Neurology in Vancouver, Canada.

The news adds to a host of recent research investigating the long-term effects—including the degenerative brain disease chronic traumatic encephalopathy, or CTE—of football-related head injuries, said study author Francis Conidi, MD, of the Florida State University College of Medicine in Tallahassee.

“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 a press release. “The rate of traumatic brain injury was significantly higher in the players than that found in the general population.”

The researchers performed sensitive MRI diffusion tensor scans, which utilize the movement of water molecules to visualize tissues, on 40 retired NFL players to determine the amount of white matter damage present in their brains.

They found that 43 percent of players had damage significant enough to be considered evidence of traumatic brain injury, with the likelihood of white matter damage increasing with the number of years spent as an NFL player.

There was no correlation between number of reported concussions and evidence of traumatic brain injury, suggesting that cumulative impacts from games and practices—and not just infrequent “big hits”—play a significant role in the extent of football-related brain damage.

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