Study Finds Cognitive Impairment in Some Retired NFL Players

A study led by the UT Dallas Center for BrainHealth examining the neuropsychological status of former National Football League players has found heightened incidence of cognitive deficits and depression among retired players.

But researchers from the center and from UT Southwestern Medical Center say their study, published online Monday in JAMA Neurology, also is significant for what it did not find: evidence of cognitive impairment in the majority of ex-players.

“Many former NFL players who took part in our study, even those with extensive concussion histories, are healthy and cognitively normal,” said Dr. John Hart Jr., medical science director at the Center for BrainHealth and director of the BrainHealth Institute for Athletes, which was created to address the long-term effects of sports-related traumatic brain injuries. “In 60 percent of our participants – most of whom had sustained prior concussions – we found no cognitive problems, no mood problems and no structural brain abnormalities. Many former NFL players think that because they played football or had concussions, they are certain to face severe neurological consequences, but that is not always the case.”

Dr. Hart, who is the study’s lead author and holds a joint appointment at UT Southwestern as a professor of neurology and psychiatry, said the investigation is the largest comprehensive study of former NFL players using neuropsychological testing, neurological assessments and neuroimaging.

Former Dallas Cowboy fullback Daryl Johnston, who participated in the study and helped recruit other players to take part, said: “Having played 11 years in the NFL and taken countless hits, I’ve heard about the struggles of the players who came before me and the challenges regarding their quality of life. Through the Center for BrainHealth, former players can find out if there is an issue, and if you catch it early or late, there are things you can do to improve your condition. The brain is regenerative for life, and we can restore faculties that just a few years ago were thought to be lost forever.”

Since 2010, 34 ex-NFL players with a mean age of nearly 62 underwent detailed neurological and neuropsychological assessments measuring aspects of intelligence, cognitive flexibility, processing speed, language skills, memory and mood. Researchers also gathered detailed retrospective histories of mental status and concussion experiences, and examined motor and sensory functions, gait and reflexes. Twenty-six of the ex-players also underwent detailed diffusion tensor MRIs. All but two of the 34 players reported having experienced at least one concussion, with 13 as the highest reported number.

Also noteworthy was that, for the first time, researchers identified a correlation between cognitive impairment and cerebral white-matter abnormalities. Among the players who were found to have cognitive deficits or depression, researchers found disrupted integrity in their brains’ white matter, which is connective tissue that allows information to travel from one brain cell to another. There were also associated brain blood flow changes in those who developed cognitive impairments, providing clues to the active brain changes resulting in deficits.

Some of the players do have some form of cognitive impairment. Four were diagnosed as having fixed cognitive deficits, eight as having mild cognitive impairment and two had dementia. When compared to healthy, age-matched control subjects, the former football players generally had more difficulty on neuropsychological tests that dealt with naming, word finding, and visual and verbal episodic memory.

About 24 percent of the players were diagnosed with depression, including six who never before had been diagnosed or treated. The rate of depression in an age-matched general population would be about 10 percent to 15 percent, said neuropsychologist Dr. Munro Cullum, the study’s senior author and a professor of psychiatry and neurology at UT Southwestern.

The findings could have implications beyond the football field, particularly in the areas of aging and Alzheimer’s disease, Dr. Cullum said.

“There is still so much we don’t know about concussions and later-life function, nor do we know who is vulnerable to cognitive problems later in life,” Dr. Cullum said. “Severe and moderate head injuries have been identified as a potential risk factor for Alzheimer’s. We’re still learning about concussions.”

Other researchers on the study included Dr. Nyaz Didehbani, Dr. Elizabeth Bartz, Jeremy Strain, Heather Conover and Sethesh Mansinghani, all of UT Dallas; Dr. Kyle Womack, who holds appointments at both UT Dallas and UT Southwestern; Dr. Hanzhang Lu of UT Southwestern; and Dr. Michael A. Kraut, who holds appointments at both UT Dallas and the Johns Hopkins University School of Medicine.

The study was supported by the BrainHealth Institute for Athletes at the Center for BrainHealth.