More Evidence Retired NFL Players Face Increased MCI Risk

Susan Jeffrey

July 18, 2011

July 18, 2011 (Paris, France) — A new study finds up to a third of a group of retired National Football League (NFL) players meet criteria for mild cognitive impairment (MCI), despite an average age of 61 years.

The conclusions are 2-fold, lead author Christopher Randolph, PhD, a neuropsychologist and clinical professor of neurology from Loyola University Medical Center in Chicago, told a press conference here.

"Cognitive impairment seems to be more prevalent in retired American football players, professional football players, than in the general population that age, where you just do not see rates anywhere approaching 35%," Dr. Randolph said.

Dr. Christopher Randolph

"And secondly, the profile of impairments in the NFL sample is very, very similar to clinically diagnosed mild cognitive impairment. To me, this suggests that these players may simply be exhibiting earlier clinical expression of mild cognitive impairment, which we frequently think of as a prodromal form of Alzheimer's disease, and in my opinion, probably due to diminished cerebral reserve, although that really remains to be determined."

The study will be presented here at the Alzheimer's Association International Conference 2011 (AAIC 2011).

Cumulative Effects

Dr. Randolph and colleagues reported in 2005 that retired football players appeared to be at increased risk for MCI and Alzheimer's disease (AD) in later life. "We hypothesized at the time that this might be due either to repeated concussions or the cumulative effects of repetitive head trauma, because this is a sport that involves a lot of repetitive minor head trauma," he noted.

They and others have also reported results from studies in which accelerometers have been embedded in the helmets of football players to measure the angle and momentum of head trauma. "And it was kind of a surprise to us; we found that the average college football player incurred over 1300 blows in excess of 10 g every season, and that about 250 of these were in excess of 30 g, which is pretty significant."

A career that spans high school, college, and then professional football could involve substantial repetitive trauma.

In this study, the investigators first surveyed all retired NFL players who were members of the NFL Players Association (3729) about their general health in 2001. The response rate was 68%, considered a good response, and it was on the basis of this survey that they reported the 2005 paper showing increased incidence of MCI and AD.

Then in 2008, they sent a second survey to all responders older than 50 years of age — about 905 players — and 633 (70%) returned the second survey.

The surveys included the AD8, a screening tool completed by an informant, in these cases a spouse. A score of 2 or higher on this scale is considered suggestive of significant cognitive impairment. Of the 633 surveys returned, 513 had the AD8 completed.

"In our survey, 35% of our players had a score of 2 or higher that we found startling," Dr. Randolph said. "It's particularly unsettling because these are relatively young individuals. Their average age is 61."

AD8 Score Reported by Spouses for Retired NFL Football Players

AD8 Score Players (%)
0 53
1 12
2 or more 35

The researchers then conducted a telephone follow-up to recruit some of the players for a clinical trial of MCI they are planning and to further characterize the cognitive problems by using neuropsychological testing. For this they used the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS), a tool that can distinguish between different types of dementia.

Forty-one retirees agreed to be further evaluated at the University of North Carolina at Chapel Hill Center for the Study of Retired Athletes. They were matched with 41 healthy control NFL players on the basis of age, education, sex, and race, and 81 nonplayer patients with confirmed MCI who were significantly older than the retired players.

The investigators found that the profile of cognitive impairment in the retired football players was very similar to that of clinically diagnosed MCI. For example, for delayed memory, perhaps the most sensitive measure of memory function, patients with MCI had a score of 75, which would fall into about the 5th percentile of normal, Dr. Randolph said. "Retired NFL players had scores in the mid-80s, which is probably around the 15th percentile of normal for their age, and well below their comparative group, which was right at 100, the normal mean."

Still, despite the retired players' memory scores, they were still highly functioning, with an average IQ of 106, he noted.

Findings Preliminary

Dr. Randolph cautioned that their findings should be considered preliminary. The control group was not large, and it's known that retired NFL players, most of them big men, have higher rates of comorbid conditions also known to be associated with later cognitive impairment, such as hypertension, obesity, and diabetes, than seen in the general population.

"So really we need some very carefully controlled studies in order to elucidate the risks and predictors and the neuropathological substrate of cognitive impairment in this group, and we're getting ready to undertake a larger controlled study," he concluded.

How repetitive trauma leads to increased risk for cognitive disorders in later life is the subject of some debate. One hypothesis that Dr. Randolph is inclined to believe is that brain cell loss can rob individuals of cerebral reserve, leading to an earlier expression of MCI and AD.

"Another hypothesis is that it's a unique pathology, and something called chronic traumatic encephalopathy has been discussed, and that might eventually be a clinically distinct disorder, something a little different than Alzheimer's disease," he said.

In an interview with Medscape Medical News, however, Dr. Randolph expressed some skepticism about chronic traumatic encephalopathy and concern about the lack of blinding in the ongoing brain autopsy study at Boston University in which many former NFL players have agreed to participate.

"They seem to find this pathology in the brains of most people they look at, even teenagers who have never had a concussion, so I think we need more systematic study of that phenomenon to be able to reach any conclusions," he said.

"One of the things we'd like to do with a larger study with controls is to follow these people prospectively and have brain donations and do blinded pathology and see what's going on actually."

Findings Not Generalizable

Asked for comment on these findings, William Thies, PhD, chief medical and scientific officer of the Alzheimer's Association, cautioned that little can be gleaned from them for the population at large.

"That's a very narrow segment of the population with many characteristics that may lead to confounding error," Dr. Thies said. "The fact that people who do that sort of thing have an almost altered physiology, that they're natural risk takers, and that they have a very obscure and undiscoverable pharmacological history, would all confuse that data, so we shouldn't generalize that to anybody; we should look at that as a workplace issue rather than a warning for the public," he said.

Dr. Randolph agreed that this population is a specialized one.

"You of course have to remember that these football players often lead tumultuous lives," he said. "A lot of them come from difficult [socioeconomic] backgrounds, and they're plunged into a different world — there's a lot of money and then all of a sudden it's gone." As a result, the risk for psychological difficulties and drug abuse is high even among those without head injury, he said.

Alzheimer's Association International Conference 2011 (AAIC 2011). Abstract P3-112. To be presented July 19, 2011.

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