What are the risk factors for chronic traumatic encephalopathy (CTE), the long-term degenerative brain condition we have heard so much about in the sport of football in recent years? And what should athletes and their parents do to minimize the risk?

As I was gathering research for my book That’s Gotta Hurt: The Injuries That Changed Sports Forever, I had the great fortune to speak to Dr. Robert Stern, Professor of Neurology, Neurosurgery, and Anatomy and Neurobiology at Boston University School of Medicine. Dr. Stern is the Director of Clinical Research for the BU Chronic Traumatic Encephalopathy (CTE) Center. Much of his research focuses on the long-term effects of repetitive brain trauma in athletes. Here is an excerpt from that interview.

Dr. David Geier:     Could you tell me a little bit about the studies that you released this year looking at the former NFL players that started playing tackle football before age 12 and what the implications of those studies potentially are?

Robert Stern:     These two papers are from my larger study funded by the National Institutes of Health that I received a few years ago, aimed at developing ways of diagnosing CTE during life. As a side note to that study, we are also trying to understand potential risk factors for CTE. What I mean by that is there’s this one thing that we do know about CTE and that is that every individual who has had a neuropathologically-confirmed diagnosis of CTE has had one thing in common, and that is a history of repetitive hits to the head. What that translates into is that exposure to repetitive head impacts is a necessary variable for the development of CTE but it is not a sufficient variable. In other words, not everyone who hits their head a bunch is going to get this neurodegenerative disease.

A major goal of my research is to figure out why one person might be prone to get it and another person isn’t. What are the specific types of risk factors that have an impact on that? We are looking at two different areas. One is genetics and the other is things specific to the exposure history. Exposure meaning hits to the head in some way or another that might have led to brain trauma.

In this larger study, The DETECT Study, we have this interesting group that we are examining in great depth because they are likely high risk for having CTE because they all played a minimum of 12 years of football, a minimum of two years in the NFL. They’ve played positions that we know have the greatest frequency of hits, based on accelerometer data in college players, at least. They all were symptomatic before they came to Boston for the study, meaning they acknowledged having some type of difficulty in thinking and mood and behavior.

We have those people who were coming in as part of a larger study, and we also have a control group of people who have never had any exposure of any types of hits in the head. For these two published papers, we focused on one specific aspect of exposure, meaning the age of first exposure to tackle football. Why did we want to look at that? There is a fair amount of research out there, over many years, that have examined the developing brain and has shown that between the ages of around ten and twelve, in boys, the brain is going through an enormous amount of development and maturation. Additional research has shown that if the brain is injured in some way during that critical time, there may be greater consequences than the brain being injured at other times.

My PhD student at the time, Julie Stamm, who is the first author of both of those studies, took that idea that there may be this critical window of neurodevelopmental vulnerability during that pre-adolescent time period during which, if the brain is hit repetitively there may be some long term consequences.

With our DETECT participants, these former NFL players, we had a whole bunch of people in middle age, they are all between the age of forty and sixty-nine, who are currently symptomatic and at a time in their life when maybe if something was going to be going on in their brain, it might have already started. A bunch of them started to play tackle football before age twelve and a bunch started at twelve or older. What we did was we made pairs of former NFL players. Each pair being the same age, meaning both people in a given pair currently the same age, but one member of the pair started playing football before age twelve and the other member of the pair started playing at age twelve or older. Does that make sense to you?

Dr. David Geier:     Yes.

Robert Stern:     In the first study that was published in Neurology, we specifically looked at their cognitive functioning. What we found was the guys who started playing tackle football before age twelve were significantly worse on tests of memory, problem solving, and estimated verbal intelligence compared to the ones that started playing at twelve or older. Of course, that’s after statistically controlling for the total number of years of playing football. That was interesting in itself, suggesting that maybe there is this window of vulnerability.

Doctor looking at brain MRI

We then wanted to then see something about the brain, to see if there is something structurally different between the two groups.

We looked at a very specific part of the brain that we know undergoes a tremendous amount of maturation during that time period of ages ten to twelve. That is the corpus callosum, which is the fiber track bundles that carry information between the two hemispheres of the brain. What she found was that the folks who started playing football before age twelve had significantly worse alterations of the integrity of these brain structures compared to the ones who started playing at age twelve or older.

That’s a very long-winded detailed description of the two studies. What it says in summary, is that in a select group of NFL players currently in middle age, the ones who started playing football before age twelve had worse cognitive functioning and greater alterations of brain structures than the ones who started playing at age twelve or older, so that’s the first answer to your question.

The implications have to be taken with a grain of salt because this is a very select group of people. These are people who went on to play professional football, and who participated in this study, and who are in this age group now. In other words, it can’t be generalized to people who only played up to high school or only played up to college. It can’t be generalized to people who are playing the sport now, because it is a different era for how this sport is played, for better or worse.

Dr. David Geier:     It makes sense.

Robert Stern:     What it does say in my mind is it begins to answer how our hypothesis, which is if you expose the developing brain to repetitive head impacts during a potential critical window of vulnerability, there may be later life consequences. Much more research needs to be done to examine that question in greater detail and with more generalizable groups of people.

With that said, however, when I take my scientist hat off and my normal person hat on, I have to ask, does it make sense to expose our children to repetitive hits to their head during a time when we know their brains are developing in an extensive fashion?

We do everything else to protect our kids, to make sure they are safe in all ways. It’s amazing all the things we do in our society to improve the safety of our children and to make sure they have the very best health and are injury free and have the best possible outcomes in life. And yet, as a society we condone dropping kids off at a field where they then hit their heads over and over again, in a sanctioned fashion.

With that view of it, I guess for me personally, it’s not about the results of this set of research studies, it’s a personal decision by each parent to make.

Do we wait for the umpteen years required to do prospective longitudinal research studies before making personal decisions about whether we want our kids to have their heads hit during a potentially vulnerable time? That decision making is a difficult process because there are tremendous benefits of participating in football as well as all other sports. Health benefits, of being active, the confidence building that takes place, the teamwork value, the leadership skills – all of those things are tremendously important, not to mention allowing our children to follow their passions. If there is an alternative to inactivity that results in fewer repetitive hits to the head in which the kid can gain all of those other skills and traits, then maybe we should look at that.

Dr. David Geier:     Do you think that it’s more the repetitive subconcussive blows than the traumatic concussions that get diagnosed and the athlete’s held out for several weeks?

Robert Stern:     Correct. It’s been fantastic, the amount of growth and change and awareness that has taken place with regard to concussions, and concussion management, and awareness, and return to play. When it comes to long consequences in terms of this neurodegenerative disease of CTE, it does appear that it is the overall, it has something to do with the overall exposure to repetitive head impacts, not just the ones that result in symptoms of concussion.

There are several individuals who have neuropathologically-confirmed CTE post mortem, who never had any reported or observed or diagnosed concussions. Our ongoing research continues to support that. For me, I’m not really concerned about concussions. Concussions are important in terms of the necessary, immediate management and treatment and they have to be taken very, very seriously. When it comes to CTE, I am much more concerned about all of those subconcussive types of hits that nobody ever talks about.

Youth football game

Dr. David Geier:     What could football as a sport do, and maybe the NFL, do with all of this? Should they be more proactive in talking to parents of young kids or should they do more for their current players with what we know now?

Robert Stern:     There’s a big difference between the NFL and the rest of the world. The NFL is a tiny, tiny percentage of the people who play football. In fact, the NFL has really been the leader in making change, in many ways. They agreed at the last collective bargaining agreement to reduce the amount of full contact practice by a tremendous amount and that’s one of the single most important things that could be done to reduce the overall exposure to hits to the head. They are making a tremendous amount of change in terms of concussion awareness and management and return to play activities.

There are other things, though, that I think need to be done. The first part is education and awareness of society that we are not really focusing on symptomatic concussions and the big hits when it comes to, at least CTE. People need to be aware of that. We are talking about repetitive subconcussive types of trauma and that requires different types of changes, like the limited full-contact practice. Perhaps starting those types of hits at a later age, like what we were talking about earlier. A whole bunch of awareness and education to coaches, to parents, to the kids, to school systems, across all different levels of play about what we know and what we don’t know about the long-term complications of repetitive hits in football.

Dr. David Geier:     I guess that’s pretty much everything I had. If there’s, and you may not have anything you wanted to share, but if there is anything either that we didn’t talk about or a message that you’d give to parents or young football players, I’ll give you the last word as far as anything you want to add.

Robert Stern:     The message is that the science remains in its infancy with so much more ahead of us to understand. Yet, it makes logical sense in my mind to reduce our children’s exposure to brain trauma overall and that includes repetitive impacts to the head which may result in that brain trauma. Everyone needs to come up with their own individual balance of weighing the pros and the cons of playing any sport or engaging in any activity that might increase the risk for later life problems.

Dr. David Geier:     Terrific. This has been terrific. I really appreciate this terrific insight.

Learn more from Dr. Stern and other brain experts about concussions, CTE and steps football can take to protect the health of the athletes in That’s Gotta Hurt: The Injuries That Changed Sports Forever. Click here to get your copy!