Account for Variance in Concussion Tolerance Between Individuals: Comparing Head Accelerations Between Concussed and Physically Matched Control Subjects
Rowson S, Campolettano ET, Duma SM, Stemper B, Shah A, Harezlak J, Riggen L, Mihalik JP, Guskiewicz KM, Giza C, Brooks A, Cameron K, McAllister T, Broglio SP, McCrea M. Ann Biomed Eng. 2019 [Epub ahead of print]
Take Home Message
Prior to a concussion, football athletes experience more head impacts at higher magnitudes compared to non-concussed athletes with similar characteristics.
Investigators have reported a wide range of head acceleration during head impacts that cause a concussion. Further, investigators have reported that cumulative head impacts may also lead to a concussion. However, it is still unknown why some athletes suffer from cumulative or low magnitude head impacts and others do not. Therefore, the authors of this study examined the biomechanics of concussion in football when carefully selecting healthy controls for factors that may alter concussion tolerance. Athletes were selected from the Concussion Assessment, Research, and Education (CARE) Consortium cohort, which included 502 Division I collegiate football players from 4 universities and 2 military academies. These players had completed demographic reports and wore helmets equipped with head accelerometers between 2015 to 2017. Forty-four athletes that sustained a concussion were matched as closely as possible by body mass index, age, race and number of previous concussions. The authors focused on the time between the first day of practice and the date of a concussion for each matched set of players (concussed and healthy).
Athletes with a concussion experienced ~94 more head impacts and participated in ~4 more contact sessions compared to controls. Additionally, the athletes with a concussion suffered more severe contacts than controls. The authors performed a second analysis with just 24 of the best matched pairs. Among these 24 pairs of athletes, the athletes with a concussion had on average 205 more head impacts and greater head acceleration (~7g).
The authors reaffirmed that athletes with concussion experience greater head impact frequency and acceleration compared to their matched counterparts. They were also involved in more contact practices/games. The authors findings are novel because they tried to control for factors that may alter someone’s concussion tolerance; however, they had to make several large assumptions and may have missed other important factors (example: genetics). The author’s approach acknowledged that we may lack specific concussion head impact tolerances/thresholds because large cohorts hide the individual factors that increase risk such as physical traits. However, combining height and weight and matching by BMI may not be the best way to control and match for physical traits. For example, the physical attributes (muscle mass vs. adiposity) of an 18-year-old football player may not be the same as a 23-year player with the same BMI and concussion history. Additional efforts should be made to investigate other traits that may increase risk to poor head impact tolerance. Despite these limitations, this study reinforces the idea that clinicians should be aware that prior head impact may influence the chance of getting a concussion. Hence, we need to do more to encourage helmet-less practice drills and/or limiting the number of contact practices.
Questions for Discussion
Do you think these physical traits increase the risk of concussion? What additional factors do you think contribute to an athlete’s head impact tolerance?
Written by: Jane McDevitt
Reviewed by: Jeffrey Driban
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