Are Repeated Concussions Killing Football Players?

This article was originally posted on RealClearScience.

Several high-profile suicides among former NFL players have stirred a debate over whether or not repetitive concussions in violent sports such as football can cause cognitive decline later in life. This neurodegenerative condition has been called CTE, or chronic traumatic encephalopathy.

Boston Globe sports writer Bob Ryan recently penned a very provocative article about America’s most popular game. In it, he lamented the violent nature of football and the fact that almost every player, at some point, gets injured. He then went on to say this:

Football has an enormous appeal to many people who are borderline psychopaths in a manner that no other sport — and this includes the very virile sport of hockey — does not.

That is an absurd statement. First, it is quite unlikely that the medical research community has any data on which sport psychopaths find most enjoyable. Second, I am forced to conclude that Mr. Ryan has never attended a South American soccer match, one of which resulted in the beheading of a referee. (Of course, the fans thought the decapitation was justified since the referee had just murdered one of the players.) In Poland, soccer hooligans regularly beat each other up. Some of them aren’t even fans of the game; they simply engage in the activity as some sort of demented pastime.

Setting aside Mr. Ryan’s dubious analysis, though, there is a legitimate enough reason to wonder if getting bonked in the head over and over causes long-term damage. Let’s leave behind the anecdotes. What does the science say?

Unfortunately, not much. A recent article by Stella Karantzoulis and Christopher Randolph in Neuropsychology Review examined the evidence. CTE isn’t a “new” disease; it’s been recognized for several decades in boxers and referred to as “dementia pugilistica.” However, the trouble with drawing any connection between sports concussions and neurodegenerative disease is the fact that most studies have been done, as the authors say, out of convenience. In other words, typically only athletes who were suspected of having CTE are autopsied. This introduces an enormous bias into the rather limited evidence base.

Other problems for a football-CTE link include: (1) The rate of suicide among former NFL players is actually lower than the population at large; (2) the symptoms of CTE are similar to other neurodegenerative diseases, such as Alzheimer’s; and (3) there is no medical consensus about the distinguishing features of CTE. For instance, the presence of a clump of proteins called tau in the brain (tauopathy) is used to diagnose CTE, but tauopathy also exists in Alzheimer’s and nearly two dozen other diseases.

Of course, none of this is to say that sports concussions don’t cause CTE. Maybe they do. Or maybe CTE doesn’t really exist. It could be that repetitive concussions trigger neurodegenerative disease in individuals who are already genetically predisposed toward it. There just isn’t enough scientific evidence to conclude one way or the other. Long-term cohort studies are needed to settle this issue.

Please keep that in mind next time you hear about how football is supposedly causing former players to commit suicide.

Source:  Stella Karantzoulis & Christopher Randolph. “Modern Chronic Traumatic Encephalopathy in Retired Athletes: What is the Evidence?” Neuropsychol Rev. Nov 2013.