All but one of 111 former pro football players had brain injury CTE in study The study looked at the players from high school to pro levels.

 -- “Football is not a contact sport, it’s a collision sport.”

These words, spoken by legendary football coach Vince Lombardi, have taken on new meaning in the last decade after several recent studies have revealed a link between the repeated collisions for which the game is known and a progressive brain disease called chronic traumatic encephalopathy, or CTE.

Now, a new report from researchers at Boston University suggests that this often devastating neurological disease may be even more common to the sport than previously thought.

In the largest study of its kind to date, researchers examined the brains of 202 deceased football players –- ranging from high school to professional levels –- to look for tell-tale signs of CTE, a diagnosis that can only be made after an autopsy. A full 87 percent of these ex-players had evidence of CTE. The proportion was highest in professional players; of the 111 former NFL pros included in the study, 110 met the criteria for a CTE diagnosis.

But the study’s lead author, Dr. Ann C. McKee, said that one of the most alarming findings is that nearly one quarter of the 14 high school players in the study had CTE.

“The finding that the earliest beginnings of CTE can be found in high school indicates that things can go wrong at a very young age,” she said.

Dr. Gil Rabinovici, a neurologist at the University of California San Francisco, who wrote an accompanying editorial to the study, also expressed concern.

“From a public health perspective, this is a much bigger problem, since very few players make it to the professional level,” Rabinovici said. “The question everyone has is, ‘Is there a risk in playing youth football?’”

Researchers also conducted questionnaires with players’ loved ones after their deaths to assess for hallmark symptoms of CTE, which can manifest as cognitive, behavioral, or mood problems. Among players who had evidence of severe CTE, 85 percent had symptoms of dementia and 89 percent had mood disturbances.

“A lot of these guys with even early CTE were very symptomatic –- they have impulse control, rage and explosivity," McKee said, adding that mood disturbances were often severe. One in three players with CTE had signs of suicidality, which means thoughts, attempts or completions of suicide.

Additionally, the study found that CTE occurred in isolation only about half of the time. The other half of cases had evidence of an additional neurological disorder like Alzheimer’s disease, Parkinson’s disease or ALS.

“It makes one wonder how these diseases are related,” Rabinovici said. “The findings suggest that repeated traumatic brain injury could be a risk factor for many of these other diseases. We already know that the prevalence of Alzheimer’s disease, for instance, is shifted about 10 years earlier in football players.”

But though the high prevalence of CTE identified in this study was striking, it involved only subjects whose families consented or even volunteered to have their loved ones’ brains studied. These family members may have noticed concerning neurological or psychiatric symptoms in the players, and may have been looking for answers, which means that no conclusions about the overall prevalence of CTE in football players can be made.

“[The study] undoubtedly overestimates the prevalence of CTE,” lead author McKee said. “It’s a skewed population based on the fact that many of these players had symptoms.”

Still, she sees the striking results as a call to action.

“I don’t think it’s debatable whether this disease exists,” she said. “Though our findings raise more questions than answers, it’s time to come together as scientists to combat this disease.”

Nicole Van Groningen, M.D., is a hospital medicine fellow at the University of California, San Francisco.