A new study by a Chicago-area researcher casts doubt on the idea that football players are suffering the degenerative brain disease known as chronic traumatic encephalopathy, but the findings still show an elevated risk of cognitive problems later in life.

Christopher Randolph, a neurology professor at Loyola University Chicago Stritch School of Medicine, and his colleagues found that ex-NFL players who showed signs of cognitive problems appeared no different than a group of older people with the same issues. There was no sign of CTE, a condition that has been diagnosed in some troubled former football stars who committed suicide.

"There's basically no evidence that there's any unique disease that affects retired NFL players," he said.

Randolph is a well-known critic of the concept of CTE, saying the condition's biological hallmark — tangles of a protein called tau — is also present in the brains of older people who have no cognitive problems. The supposed symptoms of CTE — including aggression, impulsiveness and memory loss — are so broad as to be meaningless, he has said.

Other experts take strong exception to Randolph's conclusion, saying the vast majority of researchers believe that CTE is a distinct condition and that it has not been found in anyone who did not have a history of repetitive brain trauma.

The latest study surveyed hundreds of ex-NFL players over the age of 50, giving them a screening test meant to discern if they have cognitive impairment. About 35 percent — a surprisingly large portion, Randolph said — showed signs of trouble.

The scientists followed up with more rigorous neuropsychological testing of 41 NFL retirees who appeared to have cognitive impairment, comparing them with older people who also had impairments but who had never played a professional contact sport.

The test results of the two groups were very similar, leading Randolph to conclude that the brain problems plaguing some ex-NFL players is the same kind of cognitive trouble suffered by many older people.

He acknowledged, though, that the high percentage of former players who showed signs of impairment was a potential danger sign. It could be evidence of "diminished cerebral reserve," in which years of blows to the head leave ex-players more susceptible to diseases like Alzheimer's and Parkinson's, Randolph said.

More study on the subject is needed, he said.

"If there is any increased risk, I don't believe it's all that higher (than the population at large), but I still want to take a look at it," he said.

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