Yesterday, The New York Times broke a story about a study that seems to add to mounting evidence that playing in the National Football League increases the risk of dementia later in life. The study, commissioned by the NFL and conducted by researchers at the University of Michigan, found that the proportion of former NFL players who had been diagnosed with a dementia-related disorder (according to their own accounts) was five times higher than that in the general population for players ages 50 and older, and 19 times higher for players between the ages of 30 and 49.
On one hand, the news suggests that the NFL, after long dismissing the problem, is now taking the issue more seriously. Yet The Times may have exaggerated the importance of the dementia findings, says lead author David Weir. Dementia wasn't the focus of the study, and if it had been, it would have been designed differently. The goal was to get an overall picture of retired players' physical and mental well-being, and researchers concluded that retired NFL players are generally a happy and healthy lot.
The dementia figures are based on a single question, posed to 1063 players in a telephone survey, that asked if they'd ever been diagnosed with “dementia, Alzheimer’s disease, or other memory-related disease.” In the 50 and older group, 6.1% of former players responded affirmatively, compared with 1.2% of men in the general population. In the younger group, the reported prevalence of reported dementia was much lower, but the difference between players and non-players was greater: 1.9% vs. 0.1%. The study has not been peer-reviewed, and because it was conducted by telephone, the researchers had to rely on the players' own accounts of their medical histories, which may or may not be accurate.
At the same time, the findings fit with several other lines of evidence that have emerged in recent years suggesting that head injuries on the playing field can lead to problems many years later. (For an overview of this research, see this recent article in Science).
The Times has doggedly followed this issue and yeserday's article prominently highlights the fact that the Michigan study is the first one commissioned by the NFL to publicly report evidence of a link between football and dementia.
Indeed, in the past the NFL has been quick to dismiss signs of trouble when they've come from other researchers. For example, in 2005, when neuropathologist Bennet Omalu and colleagues reported signs of neuropathology reminiscent of Alzheimer's disease in a former NFL player who died of a heart attack at age 50, Ira Casson, a Long Island neurologist and co-chair of the NFL's committee on mild traumatic brain injury, co-authored a three page rebuttal that concluded by urging Omalu to retract or revise the paper.
Other researchers have since confirmed Omalu's basic findings in other players, and two large survey studies led by Kevin Guskiewicz at the Center for the Study of Retired Athletes at the University of North Carolina, Chapel Hill, reported a link between the number of concussions suffered on the field and higher self-reported rates of depression and cognitive problems in retired NFL players. In letters to journal editors and comments in the media, Casson and others affiliated with the league have dismissed such studies as flawed and inconclusive.
Other studies are now underway to directly investigate the long-term effects of head injuries in football players and other athletes, including some that will test players directly instead of relying on their own reports. Centers for such research have recently been established in Boston and West Virginia, and Casson says the NFL has its own study underway with 120 retired players. "The jury is still out," he told me in an interview in July. "But the evidence certainly bears further investigation."
Yesterday, the NFL released a statement responding to the Michigan study that highlights the more positive findings and points out the limitations of a self-report survey, yet also seems to acknowledge a need for more research.
Some researchers see signs that the NFL is starting to take the issue more seriously, if not yet as seriously as some would like. "I think the new commissioner [Roger Goodell] has done a great job," Guskiewicz told me in July. Goodell took over in 2006, and in 2007 convened a meeting on head injuries that for the first time brought outside experts together with NFL doctors and the league's mild traumatic brain injury committee. "The question I asked at the end of that meeting, which at times got a bit heated, was how could the members of that committee sit there and stare a player in the face and tell them that they are at no greater risk for neurodegenerative disease than the general population when all these studies have come out suggesting that at least it needs to be explored further?" Guskiewicz said. "What we've seen since that point is that they've been more open to looking into the problem."