“The whole idea with this was to look at the earliest and first things that are happening in the brain in young individuals who played these contact sports, and what we ended up finding is that these changes are occurring before CTE, or even independent of CTE,” Cherry said in an interview Wednesday.
“So it was really showing us that it’s not all about just these CTE changes,” he said. “There’s this repetitive head impact-induced change that we’re seeing, which is concerning.”
The repetitive head hits cited in the study differ from the major blows that are often associated with head injuries and concussions.
“We’re not talking about concussions, we’re talking about the sub-concussive or non-concussive injuries that people can receive hundreds of times in a month,” he said. “We’re talking about football or heading [the ball] in soccer or getting checked in hockey, all these things that are part of the sport that can happen thousands of times … not just the one or two big hits.”
To identify the earliest changes resulting from repetitive head impacts, the research team performed single nucleus RNA sequencing on the frozen human brain tissue of 28 men between ages 25 and 51, according to a BU statement announcing the study.
The brain tissue samples were divided into three groups: a control group of eight men who didn’t play contact sports; a group of eight former football players and a soccer player, none of whom were diagnosed with CTE; and a group of 11 contact-sport athletes with low-stage CTE, according to the statement.
Athletes diagnosed with low-stage CTE had significant inflammatory and vascular changes, which has been reported in the past, but the new study found similar levels of vascular injury and inflammation in athletes without CTE, suggesting that brain injury brought on by repetitive hits is not solely dependent on CTE, according to the statement.
“We went into this thinking we’d see more subtle things that are occurring because some of these individuals are in their 20s and we didn’t think they’d have any severe degenerative change, but we saw much more inflammation than expected, cell loss, blood vessel damage, and blood vessel dysfunction,” Cherry said.
“The fact that it was there before [CTE] in the level that we saw was fairly surprising to us,” he added.
The study was peer reviewed by Josh Morganti, an assistant professor in the neuroscience department at the University of Kentucky’s College of Medicine. In a phone interview Thursday, Morganti said the study’s findings suggest potential for therapeutic interventions.
“There’s a modifiable set of pathways or things that are happening in the brain that have been identified by this group, and so it sets up that there is now potentially some avenues that folks can think about developing therapeutics to target to prevent that full-on movement toward full CTE, high-burden pathology,” Morganti said.
Researchers also found a 56 percent loss of neurons at the “cortical sulcal depths” of the brain — “the regions that undergo the highest mechanical forces during head impact injury” — in athletes who competed in contact sports, according to the study. Cherry said neurons in this part of the brain are important for moving signals and “have a role in attention [and] some sort of behavior and decision-making processes.”
The study found neuron loss in all athletes, regardless of whether they had CTE.
“It’s not all the cells [in the brain], just some of them, so it’s not going to be completely disruptive but we think it has a chance of being involved in slight impairment that we might see in young individuals,” he said.
As awareness around brain injuries and concussion prevention in sports has increased over the past couple of decades, a question that many have is what age is it appropriate to enter contact sports, if at all?
“I don’t think we can ever talk about a ‘safe age,’ it’s always about minimizing risk,” Cherry said. “Maybe having kids start playing later in life or more flag football, or for soccer less heading. Any way we can minimize risk is going to be really important, even in these young individuals.”
Nick Stoico can be reached at nick.stoico@globe.com.
