Published December 12, 2013
Many studies have demonstrated the devastating, long-lasting health implications associated with concussions. Now, a new study published in the journal Neurology indicates that even head blows that don’t result in concussions can cause differences in athletes’ brains – over the course of just a single season.
Study author Dr. Thomas W. McAllister became interested in studying the effects of non-concussion head injuries after realizing that the strength of a head blow didn’t necessarily correlate to an athlete's chances of experiencing concussion.
“We had this originally sort of naïve idea it would be easy to find a threshold (of impact) above which someone was really pretty likely to get a concussion. And after studying thousands of these impacts, it turns out it’s much harder to develop this threshold,” McAllister told FoxNews.com. “So that raised questions of, if that’s the case, what do we know about the effects of these repetitive blows – some of which are quite high in magnitude. And it turns out we didn’t know a whole lot about it.”
As a result, McAllister and his colleagues decided to study how the effects of blows that don’t result in a concussion can impact the brains of athletes. For their study, they followed a group of contact athletes – including football and ice hockey players – along with a group of non-contact athletes at Dartmouth College in New Hampshire from pre-season to post-season.
During the course of the season, the contact athletes wore helmets that recorded the acceleration-time of the head following impact, in order to calculate the intensity of the head blows they received.
The researchers also conducted cognitive functioning tests and brain scans on each group of athletes during both the pre-season and the post-season. Their goal was to measure changes in memory or learning, in addition to changes in the brain’s white matter and corpus callosum – a region of the brain where white matter is concentrated.
“That’s one of the areas that you look for injury in somebody who’s had more severe brain injury,” McAllister said. “These white matter tracts, if you injure the white matter in some way, it may be the case that you’re less efficient or slower at information processing, and it may well be that that’s the mechanism underlying the change in cognition. Though, we haven’t proved that.”
When conducting scans during the pre-season, the researchers found little difference in the two groups’ white matter or cognitive functioning. Yet during post-season, there were some key brain imaging differences that correlated with the strength of the blows sustained by the athlete – even when those impacts didn’t result in concussions.
Furthermore, after post-season cognitive testing, 20 percent of the contact players scored more than 1.5 standard deviations below the predicted score on tests of verbal learning and memory at the end of the season, compared to 11 percent of the non-contact athletes.
“The good news is we’re not seeing pre-season significant differences that make us worry that there has been accumulation to date, but at the other hand, the end of the season is associated with differences associated with how hard and how often you’re getting hit. And folks doing worse cognitively are showing more of these differences,” McAllister said.
The researchers said their findings raise questions about how long these changes to the brain last after a season ends and whether or not they have a cumulative effect over time.
“I guess one analogy would be the first time you sprain your ankle, it usually recovers pretty quickly. But even without symptoms, it seems to be easier to sprain it the next time…,” McAllister said. “So what we don’t know is if given enough time, (blows to the head) start a process (like this).”
Given the evidence that even non-concussion head injuries may result in some degree of brain changes, McAllister noted that coaches and athletes need to be aware of the consequences of each and every impact.
“I think that the changes in rules, trying to eliminate excessive contact to the head, are a really good thing,” McAllister said. “I’m not sure if it’s been proven that it will decrease the number of concussions, but I think it’s a good thing, and (also) I think that it means we should begin to have an awareness that we may need to look at the effects of these repetitive impacts and not just what we are diagnosing as a concussion.”