Brain damage from football concussions varies by position and career duration

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Football players may experience different degrees of brain damage after concussions depending on what position they play and how long they stick with the sport, a small U.S. study suggests.

Researchers examined data from brain scans of 61 former college and professional football players who didn't have any symptoms of cognitive impairment. One technique, known as diffusion tensor imaging (DTI), looked at the structural integrity of white matter, which connects different parts of the brain; the other test, known as functional magnetic resonance imaging (fMRI), measured brain function while participants competed memory tasks.

Former college players with three or more concussions had more extensive white matter damage than their counterparts with one concussion or less, researchers report online October 31 in Radiology. But the opposite was true for athletes who went on to play professionally.

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"Our findings suggest that a career with additional exposure to football is not necessarily worse than a shorter duration of exposure," said senior study author Kevin Guskiewicz, research director of the Center for the Study of Retired Athletes at the University of North Carolina at Chapel Hill.

"In addition to imaging findings, there were no differences on standard cognitive tests between those players with a longer career compared to those with a shorter career," Guskiewicz told Reuters Health by email.

One of the most vexing issues with treating concussions in athletes is that the full extent of brain injuries can be difficult to assess while players are still alive. In particular, chronic traumatic encephalopathy (CTE) can only be diagnosed during an autopsy.

Most previous research on head injuries in football has focused on former athletes with cognitive impairment.

For the current study, researchers focused instead on former players who appeared cognitively healthy to see if imaging scans might reveal differences in brain damage based on the position played or the length of their careers.

Roughly half of the study participants played only college football and half continued on to the National Football League (NFL).

Half of the former players reported three or more prior concussions, while the other half reported one or no prior concussions.

Roughly half of the participants were offensive or defensive linemen, so-called non-speed positions.

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Non-speed players with a history of recurrent concussions had more damage to white matter and less brain activity during memory exercises, the study found. This wasn't the case for running backs and other speed players, however.

The interactions observed between concussion histories and playing positions suggest there may be important differences in the mechanisms of injury between speed and non-speed players, the researchers conclude.

Offensive backs experience impacts at greater acceleration, for example, while linemen tend to experience a greater overall frequency of impacts and have the greatest proportion of impacts to the front of the helmet.

The study wasn't a controlled experiment designed to prove whether or how the position played or career duration might influence the risk of brain damage after concussions.

It's also possible that players with longer careers and multiple concussions who don't develop cognitive damage by middle age may differ from former athletes who develop cognitive problems.

"Constant banging of heads in the non-speed positions might be just as dangerous as a few higher-speed type collisions that occur at the speed positions," said Jonathan Godbout, a neuroscience researcher at the Ohio State Wexner Medical Center in Columbus who wasn't involved in the study.

"That's scary because these subthreshold injuries would be very difficult to detect," Godbout said by email.