Wednesday night's NFL season opener between the Dallas Cowboys and the New York Giants comes hours after a study released by the American Academy of Neurology reveals that NFL players are three times as likely to die from neurodegenerative diseases, such as Alzheimer's or ALS, than the general population.
The study, published in the latest edition of Neurology, examined a cohort of 3,439 retired NFL players with at least five years of vested service between 1959 and 1988. Among that group they found 334 deaths; neurodegenerative diseases were found to be the cause or a contributing factor in 27 deaths.
"We looked specifically at causes of death from brain and neurosystem disorders, which are known as neurodegenerative disorders," study author Everett J. Lehman, MS, with the National Institute for Occupational Safety and Health (NIOSH) in Cincinnati, told SB Nation. "Those deaths are caused by deaths of neurons in the brain and nervous system.
"These results are consistent with recent studies that suggest an increased risk of neurodegenerative disease among football players," Lehman said.
NIOSH, part of the Centers for Disease Control, conducted a statistical examination of NFL player mortality rates in 1994 at the request of the NFLPA. That research and a follow-up report presented in 2012 found overall lower mortality rates among retired NFL players when compared with men of a similar age and racial mix. The latest study is a continuation of that research.
"We've been following this group of NFL players for almost 20 years," Lehman said. "Even some years ago we wanted to take a look at it, because there have been concerns about concussions, head injuries and possible long-term neurological problems in football players and this is a very good opportunity to explore that hypothesis."
Of the 334 deceased players, Alzheimer's or dementia was listed as an underlying cause of death for seven players. ALS was listed as an underlying or contributing cause of death for another seven players. While the overall mortality rate among former players was three times higher for all neurodegenerative diseases, it was four times higher for ALS and Alzheimer's compared to the general population.
Not included in the study is chronic traumatic encephalopathy, CTE. There is a reason for that, according to the study's author.
"Chronic traumatic encephalopathy is a relatively recently defined separate diagnosis from ALS, Parkinsons and Alzheimer's," Lehman explained. "A couple of issues with that. First, CTE can only be, with any degree of certainty, ascertained upon death and usually via autopsy of the brain. Second, it exhibits symptoms very similar to what may be found in someone who has ALS, Parkinson's or Alzheimers.
"The whole pathway, the whole Etiology behind how these diseases develop hasn't been fully teased out," Lehman said. "No one knows if CTE may be a precursor to ALS, Alzheimer's, or Parkinson's, or if it's a totally separate developing disease. We're still in the early stages of sorting that out."
CTE and other neurodegenerative diseases are getting plenty of media attention in recent months with high profile suicides by former players and a class action lawsuit filed by more than 2,000 former players against the NFL. The plaintiffs allege that the league concealed a link between head trauma and long-term neurological damage, including the types of diseases covered by this study. The NFL recently filed a motion to dismiss the case.
The most recent NIOSH study does not point to a link between concussions and neurodegenerative diseases, though there is research out there suggesting such a link.
"We did not make direct connections between concussions and neurodegenerateive disorders," Lehman said. "We just did not have specific enough information on concussions dating back these many years. But we felt like this analysis was kind of taking into account what these other studies have been finding, and that's why we analysed it the way we did."
The NIOSH study borrowed from previous studies examining the occurrence of concussions among football players. They classified players into two position groups, speed and non-speed. Players in the speed category include every position but those along the defensive and offensive lines.
"The thinking behind that is although the linemen knock heads on probably every play they're involved in, they're general short distance and low momentum hits," Lehman said. "Whereas you have a cornerback tracking a wide receiver or a linebacker zeroing in a on running back, many times they have a head start so there may be considerable momentum built up before the hit or the tackle or the block. In those studies, they found that those positions are at higher risk for concussion."
Speed position players were more than three times more likely to die from neurodegenerative diseases than the other players.
Lehman and the other authors limited the scope of their work to records. That means other factors, including environmental or genetic considerations, were not factored into the work. It may not have mattered much for the types of diseases they were studying.
"At this stage there is not much to note about those other factors," Lehman said. "There's one genetic marker that may be involved in increased risk of Alzheimers and CTE and possiblity Parkinsons, but the jury is still out on that. There really weren't that many other factors that are currently known that we could or did take into account."
Researchers at NIOSH will continue to track this cohort of retired players. Lehman expects to learn more as the years go by and more knowledge about these types of diseases is available.
"As these players age and more people die, we'll be able to strengthen these results and possibly do some additional analysis," Lehman said. "We're just getting into the stage where the results become even more interesting and informative."
The NFL announced a $30 million grant on Wednesday morning to the Foundation for the National Institutes of Health that is intended to further research on brain injuries and neurodegenerative diseases.
"Whether it's CTE or Alzheimer's or ALS or what caused what, they're all in this basket called neurodegenerative diseases," Lehman said. "They're all serious, and there's not much treatment for any of them. What we really need to do is identify and really concentrate on the causation of these diseases."