Katie Hunzinger

Repetitive Head Impact Exposure Does Not Affect Postural Control in Early to Middle-Aged Adults

Brain damage
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K Hunzinger 1

  1. University of Pennsylvania, Perelman School of Medicine, Department of Epidemiology, Biostatistics, and Informatics


BACKGROUND AND AIM: Research on the long-term effects of repetitive head impacts (RHI) has been homogenous, utilizing self-report and subjective outcome measures. Further, samples have lacked generalizability and comparison, having included primarily  collegiate or middle-aged males, with a history of playing high school or professional American football, despite evidence that females suffer worse outcomes to repetitive neurotrauma. Single task (ST) and dual task gait (DT) (i.e., gait with a cognitive task) are established measures of neurobehavioral function and known to be negatively impacted by neurotrauma and positively impacted by physical activity, providing an objective marker for neurophysiological health. Further, dual task cost (DTC), the change in performance in DT relative to ST provides insight on subtle gait and/or cognitive deficits. As such, a need exists to investigate the mid-life effects of RHI exposure using objective measures and multiple comparison groups and both sexes. Thus, the purpose of this study was to determine the effect of prolonged RHI exposure on measures of ST and DT gait among early-middle aged adults with varying levels of physical activity and RHI exposure.

METHODS: 113 adults (34.9 + 11.8 years, 53.0% female) representing four distinct groups participated in this study: those with no history of RHI who are not physically active (NON) or those who are physically active (NCA); and those who are physically active with a history of RHI through high-risk sports (HRS) or prolonged RHI exposure through rugby (RUG).  Gait data was collected using inertial measurement unit measured level-overground ST and DT gait. DTC was calculated for all gait variables (double support, gait speed, stride length). Groups were compared using a one-way ANCOVA on all gait outcomes with known covariates included in the model (concussion history, height, age, contact/collision sport career duration—a measurement of lifetime RHI exposure, learning disability history, and sex).

RESULTS: A significant effect for group existed for ST gait speed (p=0.034) and ST double support (p=0.026), but there were no post-hoc observed group differences (p>0.05). There were no significant adjusted group differences for DT gait speed, ST and DT stride length, DT double support, or any DTC outcome (p>0.05).

CONCLUSIONS: When accounting for lifetime RHI exposure, physically active individuals with a history of RHI or prolonged RHI exposure through contact/collision sport participation (i.e., HRS and RUG) do not have worse gait performance as assessed by gait in early- to mid-adulthood than physically active individuals with no history of RHI exposure (NCA). These findings highlight the potential neuroprotective benefits of physical activity against the detrimental effects of RHI throughout ageing.


concussion; collision sports; gait


Really interesting work! Its also interesting that repeated head injury did not affect gait. I am wondering if perhaps the patients are still young (average age of 34.9 years) - do you think its possible that the aging process itself may be affected by repeated head injury and overtime there may be gait changes, but those have not been detected yet as the patients are still rather young? Great work!

Mary, thanks for viewing and commenting! Excellent point--this is the concept we really hope to address in the future manuscript.

This is exactly what we are thinking. Essentially the literature has shown dysfunction in middle-older aged former football players, but some cohorts of similar age do not have dysfunction. Yet, data in collegiate athletes and the data presented herein, show that there are not any differences. However, there is some evidence of individuals with potential dysfunction in my cohort. So is this the canary in the coal mine? It's possible that some individuals may be at heightened risk for future dysfunction compared to their peers. Or, as you suggest, they may all be at risk for dysfunction and it does not manifest in mid-30s, but maybe it will at age 50/60/70. Unfortunately, the majority of the later-life data are limited to chart-analysis or cohorts of former male football or soccer players.

We are hoping to expand this work to women collision sport athletes in their 50s, so hopefully we can start to get to the answer. As it stands, it's promising that there does not appear to exist neurobehavioral dysfunction, evidenced by gait, in these physically active athletes.

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