Amid mounting concerns over the health of pro football players, a new study has shown that as many as 40 percent of retired NFL superstars could be suffering from traumatic brain injury (TBI). Set to be announced at the upcoming annual meeting of the American Academy of Neurology in Vancouver, the study will come as another blow to lovers of the game, which has recently seen something of an exodus of top players fearing for their long-term health.

While top NFL officials have pointed out that risk is ever-present in life, and that the prospect of injury is a worthwhile price for the thrill of the contest, increasing awareness of the dangers of TBI is causing many to think twice about donning a helmet and stepping onto the gridiron.

TBI is an umbrella term covering a spectrum of cognitive disorders resulting from blows to the head. Many of these are difficult to detect, partly because the marks they leave on the brain don’t show up in regular functional magnetic resonance imaging (fMRI) scans. However, in a recent study involving war veterans who had received blows to the head while on duty, researchers found that signs of long-term brain damage could be detected using a technique called diffusion tensor imaging (DTI).

DTI measures the movement of water molecules through a type of brain tissue called white matter, allowing scientists to pinpoint any areas where the flow is disrupted due to structural damage. Researchers, therefore, decided to use this technique to study the brains of 40 retired NFL players, who had played an average of seven seasons in the sport’s elite league, suffering an average of around eight concussions each during their careers.

^{Even helmets can't always protect players from brain injuries. dean bertoncelj/Shutterstock}

While 12 of these former athletes showed evidence of TBI on traditional MRI scans, 17 were found to be suffering from the condition once DTI was used. This represents a staggering 43 percent of the overall cohort.

Even more alarming is the fact that some of the participants who returned healthy scans actually showed evidence of cognitive impairment when conducting thinking and memory tests. Overall, 50 percent of ex-pros were found to have problems with executive function – which refers to general problem-solving skills – while 45 percent had learning and memory deficits.

Putting these results into perspective, study author Francis Conidi explained in a statement that “the rate of traumatic brain injury was significantly higher in the players than that found in the general population.”

Despite the fact that NFL players wear state-of-the-art helmets, scientists are beginning to realise that these are only effective at protecting the skull, but cannot prevent players’ brains from “sloshing” around inside their heads when they take a big hit. In the face of growing evidence regarding the dangers of these types of impacts, NFL commissioner Rob Goodall was recently left with no choice but to publically accept the link between football and chronic traumatic encephalopathy (CTE), a cognitive disorder that develops from TBI.

In light of this, a number of high-profile players have recently turned their backs on the sport despite apparently having their best playing years still ahead of them. Chris Borland of the San Francisco 49ers, for example, retired last year at the age of 24, and has since been followed by the likes of 23-year-old Buffalo Bills linebacker A.J. Tarpley and 30-year-old Detroit Lions superstar wide receiver Calvin Johnson.