THE BLOG
12/06/2013 11:28 pm ET | Updated Feb 05, 2014

Are There Genetic Markers for Concussions?

In an age when talk shows like The Maury Povich Show use genetic testing to determine paternity, surely there must be ways to use genetic testing for more than day-time entertainment, no? Well, there are. For one, researchers have found links between certain genes and a football player's susceptibility to getting a concussion.

It's a scientific detective story, of sorts. To figure out which genes might give us clues as to who is easily concussed, scientists first needed to understand what's happening during a concussion. In normal conditions, the brain cells, or neurons, communicate with each other by electrical and chemical signals in the form of ions.

However, when a football player is tackled, these neurons can be stretched by the blunt force, and the flow of these ions becomes erratic. Dr. Robert Stern, a professor of neurology at Boston University and one of the leading researchers in head injuries, describes a concussion in a paper as "an alteration in brain function induced by biomechanical forces."

Scientists are investigating the genes that are linked to how these ions flow, hoping that their findings will help prevent concussions in football players young and old. While researching the new book Newton's Football, my co-author Allen St. John and I talked to Dr. Ryan Tierney, a researcher at Temple University. Dr. Tierney and his group are looking into the genes that control the flow of calcium ions. "An influx of calcium [ions] can lead to neuron dysfunction," he explains. "So then you look for proteins that help control calcium. That leads you to a long list of proteins. The coding for a protein might be in more than one gene." Tierney continues: "Then the fun starts: to find the common variations in these genes."

Searching for the genes that control the flow of ions is one route that scientists are taking. But there are others. There are research reports that point to a smoking gun: a gene called the apolipoprotein E, or APOE, gene.

On a positive level, the APOE gene, which has three variations -- APOE ε2, ε3, and ε4 -- helps control the distribution of fats and cholesterol in the body. But it also seems to control the way that neurons are repaired -- or aren't -- after a head injury. "If you have the wrong form," Stern explains, "it does something crazy in the brain."

The APOE ε4 has been specifically linked to concussions and mild traumatic brain injury and is also associated with increased risk of Alzheimer's disease. One study found that there was lower cognitive performance in older football players possessing it. But, most importantly, APOE ε4 has some strange linkage to chronic traumatic encephalopathy, or CTE. This is the degenerative brain disease that's seemingly linked to head trauma and is found in many retired football players.

Tierney is targeting the role of APOE ε4 in head injuries. "We looked at 200 athletes and genotyped these 200 athletes. Of the 200 athletes, only four were carriers of [APOE ε4]," he explains. "Three of the four had had a history of concussions."

Admittedly, this is not a significant sample size, but it could provide an important clue into the mystery of concussions, and even chronic traumatic encephalopathy (CTE).

"APOE ε4 has been found to have a negative effect with people with CTE by getting in the way with neural repair," explains Stern. "It slows down the repair of brain cells." This gene, he says, "makes return to normal longer and makes it harder for the cells to get to normal."

Stern warns that the connection between head injuries and genetics is complex. "There is not going to be a CTE gene, because it is such a multifaceted kind of neurologically degenerative disease, like all of them." As for APOE ε4: "It is a susceptibility gene," he says, "as opposed to a deterministic gene. If you have the wrong form, it increases your risk of having the disease, but it does not mean you will get it."

Right now, research into APOE ε4 is providing more questions than answers. It might indicate a proclivity for concussions or CTE -- or it might not. So don't run out and get tested. At least not yet.

So what does this research tell us? That we may know soon if there is a genetic predisposition to concussions and CTE, and that knowing a player's genetic make-up might help players -- and their parents and coaches and doctors -- make educated decisions that could ultimately help prevent concussions and degenerative diseases. What we know for certain is that at the heart of football's future lies a debate about science.

Learn more about the science behind football and head injuries in the new title from Random House, Newton's Football: The Science Behind America's Game.