Cognitive effects of one season of head impacts in a cohort of collegiate contact sport athletes
The research was part of a multi-institution study that has been working for five or six years to understand the biomechanical basis and effects for concussions, McAllister said.
The study, which was published by the American Academy of Neurology, found that contact sport athletes did not perform worse than non-contact sports athletes on cognitive tests before their seasons began. These results were “reassuring,” McAllister said.
“We did not find any systematic widespread adverse affects on cognition,” he said. “The two groups on average looked pretty similar at the end of the season.”
The study did find that a larger subgroup of contact sport athletes than non-contact sports athletes performed worse than expected on tests taken immediately after the season. Taking into account how well the athletes tested before their season began and controlling for other indicators of general test performance and the interval between tests, the authors predicted how well the athletes should perform after their season and compared this to their actual results.
“We found that about 22 percent [of contact sport athletes] did worse than 1.5 standard deviations below what we would have predicted,” McAllister said. “This was a significant difference from the non-contact group.”
McAllister said that this raises the possibility that some individuals are particularly vulnerable to suffering negative effects from hitting their heads repeatedly during contact sports.
“This changes the emphasis of the debate a little bit,” McAllister said. “It’s a new direction for us to be thinking about the risks or lack of risks for contact sports. There may not be the same risk for everyone.”
The researchers also used the tests administered at the beginning of the season to see whether athletes who had been playing contact sports for most of their lives and had presumably hit their head more often had lower cognition than non-contact sport athletes.
“We did not find any systematic differences between the two athlete groups at the beginning of the season,” McAllister said. “We think this is good news. We were unable to detect widespread significant differences in their cognitive capabilities.”
To measure their results, researchers administered two tests to male and female contact and non-contact sport athletes from the College, Brown University and Virginia Polytechnic Institute and State University at the beginning and end of their seasons. Contact sport athletes played football or ice hockey while non-contact sport athletes participated in track, Nordic skiing or crew.
Participants that sustained a documented concussion during the season were not included in the study results because researchers were primarily interested in the effects of “repetitive impacts to the head not apparently causing a concussion,” according to McAllister.
A 20-minute computerized test measured cognition, memory attention and reaction time. The other neurological test, administered to a sub-group of athletes, was more extensive and used “paper and pencil.” Researchers compared the results of the contact sport athletes’ tests with the non-contact sport athletes’ tests, which were used as a control.
Contact sport athletes wore special helmets during practice and games equipped with a Head Impact Telemetry System designed by Richard Greenwald, the president of Simbex, a technology company in Lebanon. The helmets have been in use since 2004 around the United States, according to Greenwald.
“The helmets contain a system that monitors head impacts automatically and wirelessly,” Greenwald said. “They measure how often, how hard and where on the helmet gets hit.”
Jessica Gagner ’13 plays women’s ice hockey and participated in the study as a contact sport athlete. She said she was not more cognizant about hitting her head when wearing the helmet.
“To me, if you’re playing a contact sport, you’re obviously going have a bigger effect on your head,” Gagner said. “It’s really inevitable that you’re going to have more of an issue with head impacts if you are a contact sport athlete.”
Cara Vernacchia ’13 runs track and was a non-contact athlete who participated in the study. She said she was glad to be able to take part to help researchers learn more about concussions and how to prevent them.
“Being able to be part of the study made me realize that concussions do occur,” Vernacchia said. “It’s interesting to see how prominent head impacts are, even on our campus.”
The researchers hope to continue observing the effects of contact sports on the study’s participants. Many students agreed to undergo neuroimaging before and after their seasons and researchers hope to examine these results.
“We’d love to be able to revisit with some of these athletes four or five years down line and get a second set of test results to see how they’re doing after a whole collegiate career,” McAllister said.
The researchers also hope to learn more about why certain athletes performed worse than expected on tests after a season of contact sports.
“I think the second theme of ongoing research would be to try and understand what individuals are at risk to be in that ‘not doing as well as we would have thought’ category,” McAllister said.
Greenwald said that the researchers hope to learn more about the effects of contact sports on youth and women in the future.
Read more here:
Cognitive effects of one season of head impacts in a cohort of collegiate contact sport athletes
- T.W. McAllister, MD,
- L.A. Flashman, PhD,
- A. Maerlender, PhD,
- R.M. Greenwald, PhD,
- J.G. Beckwith, MS,
- T.D. Tosteson, ScD,
- J.J. Crisco, PhD,
- P.G. Brolinson, DO,
- S.M. Duma, PhD,
- A.-C. Duhaime, MD,
- M.R. Grove, MS and
- J.H. Turco, MD
+Author Affiliations
- Correspondence & reprint requests to Dr. McAllister: thomas.w.mcallister@dartmouth.edu
ABSTRACT
Objective: To determine whether exposure to repetitive head impacts over a single season negatively affects cognitive performance in collegiate contact sport athletes.
Methods: This is a prospective cohort study at 3 Division I National Collegiate Athletic Association athletic programs. Participants were 214 Division I college varsity football and ice hockey players who wore instrumented helmets that recorded the acceleration-time history of the head following impact, and 45 noncontact sport athletes. All athletes were assessed prior to and shortly after the season with a cognitive screening battery (ImPACT) and a subgroup of athletes also were assessed with 7 measures from a neuropsychological test battery.
Results: Few cognitive differences were found between the athlete groups at the preseason or postseason assessments. However, a higher percentage of the contact sport athletes performed more poorly than predicted postseason on a measure of new learning (California Verbal Learning Test) compared to the noncontact athletes (24% vs 3.6%; p < 0.006). On 2 postseason cognitive measures (ImPACT Reaction Time and Trails 4/B), poorer performance was significantly associated with higher scores on several head impact exposure metrics.
Conclusion: Repetitive head impacts over the course of a single season may negatively impact learning in some collegiate athletes. Further work is needed to assess whether such effects are short term or persistent.
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