Sports Medicine Research: In the Lab & In the Field: Cognitive Effect of One Season of Head Impacts (Sports Med Res)


Thursday, June 7, 2012

Cognitive Effect of One Season of Head Impacts

Cognitive effect of one season of head impacts in a cohort of collegiate contact sport athletes.

McAllister TW, Flashmasn LA, Maerlender A, Greenwald RM, Beckwith JG, Tosteson TD, Crisco JJ, Brolinson PG, Duma SM, Duhaime AC, Grove MR and Turco JH. Neurology. 2012. 78:1777-1784.

Recently in many media outlets, concerns have been raised over the long-term effects of head impacts on athlete’s cognitive function. While many studies have looked at the effects of mild traumatic brain injuries, few studies have looked at repetitive head impacts and their long-term effects. Therefore, McAllister and colleagues completed a pretest/posttest cohort study to evaluate if repetitive head impacts sustained over 1 season would affect cognitive performance. Two cohorts (214 contact sport [football and ice hockey] athletes and 45 noncontact sport [track, crew and Nordic skiing] athletes) from 3 participating division 1 universities were used in this study. All patients underwent testing that included the Immediate Post-Concussion Assessment and Cognitive test (ImPACT) at both preseason and postseason. Participants from 1 of the 3 universities (45 contact and 55 noncontact athletes) also underwent additional neuropsychological testing to assess general level of intellectual functioning, attention/concentration, working memory, verbal and visual learning and memory, verbal fluency, and processing speed. To measure head impacts all participants in the contact sport group were asked to wear the Head Impact Telemetry (HIT) system (composed of 6 single-axis accelerometers) in their helmets during all practices and games. The results of this study suggested that the ImPACT scores were no major differences between cohort’s scores before or after the season. Of the participants who underwent additional neuropsychological testing, non-contact athletes performed better on the Paced Auditory Serial Addition Task (assessing capacity and rate of information processing) than the contact participants during preseason, but, at the postseason follow-up, this was reversed with noncontact participants scoring more poorly than the contact sport athletes. Differences on the California Verbal Learning Test (assessing verbal learning and memory) were also observed with noncontact athletes improving more after the season than the contact participants. Analysis of the biomechanical data from the HIT system and ImPACT scores suggested a trend of poorer testing scores when the patient was exposed to more head impacts, but this did not reach statistical significance.

Overall this study supports the notion that repetitive head impacts over 1 season of competition may have detrimental effects on an athlete’s cognitive ability (based on the California Verbal Learning Test results). Interestingly, only the noncontact participants of the study were asked about a prior history of concussions despite contact athletes undoubtedly having a greater likelihood of experiencing a concussion. This begs the question: are the baseline scores truly baseline or is the athlete’s scores deviated from the scores they would have received before being subjected to any repetitive head impacts concussions? Without knowing more details about the past medical history, these finding may be statistically significant but their clinical significance cannot be truly understood. Studies similar to this, but with follow-ups over multiple seasons would be interesting and may shed some light on this matter. Despite this limitation, this study should make clinicians aware of the potential consequences that just one season of contact may have an impact on an athlete’s cognitive ability. Clinicians should be diligent in baseline testing so that they can adequately detect these subtle changes. What have you seen in you athletes? Do you think athletes experience an overall decline in their cognitive ability from the beginning to the end of the season?

Written by: Kyle Harris
Reviewed by: Jeffrey Driban

Related Posts:
McAllister, T., Flashman, L., Maerlender, A., Greenwald, R., Beckwith, J., Tosteson, T., Crisco, J., Brolinson, P., Duma, S., Duhaime, A., Grove, M., & Turco, J. (2012). Cognitive effects of one season of head impacts in a cohort of collegiate contact sport athletes Neurology, 78 (22), 1777-1784 DOI: 10.1212/WNL.0b013e3182582fe7


Anonymous said...

I find this subject matter very curious indeed. There are so many questions and we know so little. I agree with your assessment and ideas above about where to go with the next steps of this research and have some thoughts myself.
I wonder what trends the investigators might find if they looked at the concussion history of all of the athletes contained in the Impact program, as that is incorporated into the history section. I wonder if they might see anything different in people with prior histories and if the number of concussions/severity might correlate with the magnitude of change in test scores.

I also wonder if there might be a cognitive recovery period associated in between seasons, say if the tested everyone again after their summer break and analyzed their results?

What do you think?

WilliamLangston said...


In response to your discussion questions I have seen a general lack of interest and/or effort from athletes when performing preseason testing. I am speaking from two years of collegiate football experience as a player as well as four years of Undergraduate study as an Athletic Training Student. I noticed that for the most part administration of the ImPACT test was conducted for the purpose of quantity over quality so to speak. In other words the test was administered for the purpose of baseline however with intention of completion in an efficient manner. It is understandable that time is a factor given that such a large number of athletes need to complete the testing but that does not negate the fact that clinicians should still , as you mentioned, be diligent in baseline testing. I feel that this unfortunately is a common practice across the board.

In addition to the administration the testing environment was not ideal. During preseason testing a large number of athletes were placed in a computer lab to perform the preseason ImPACT test in which social interaction and distraction were possible and present. I find this to be counterproductive given that during a re-testing period after an athlete has sustained a concussion they are placed in more isolated and secluded area to re-test. I’m not saying this is the case for all schools or athletes however I believe that consistency in testing environment and administration may influence the general effort and focus of the athletes. Therefore I believe that the aforementioned could have contributed to the lower than predicted preseason scores. Of course this was only from my experience while at one undergraduate university of the Division II level. I would hope that administration of the ImPACT testing has changed, especially within this study, and become more isolated and consistent since I last took and monitored the process.

Having said that I do believe that over the course of the season athletes experience a degree of decline in their cognitive ability from beginning to the end of the season regardless of number of hits sustained. On the psychological level I believe that effort has a major role in this outcome especially if the athletes on a particular team fail to make playoffs or have not been playing as well. I would not be surprised if the lack of effort on the field translated off the field as well especially for an ImPACT test that provides little to no immediate benefit for the athlete, so to speak.

Your thoughts?

Jeffrey Driban said...

SamWalton, You bring up a really good point. I've also wondered if we monitored athletes over several seasons if we would find a cycle where after a season their performance is reduced and during the off-season they gradually improve but perhaps don't always make it back to where they were the year before (as Kyle I think suggested by questioning is the baseline testing here really a baseline level). It would be a very interesting study.

William Langston: I think you bring up some excellent points. If the baseline testing and post-concussion testing are not provided under similar conditions then can we really trust the results to be consistent if the patient does not have a concussion. This concern was raised in a recent post regarding a paper by Moser et al. (written by Jane McDevitt: These are important details to keep in mind when administering baseline and post-concussion testing.

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