The cumulative effects of prolonged repetitive head impact exposure into adulthood
Date
2022
Authors
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Journal ISSN
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Publisher
University of Delaware
Abstract
BACKGROUND: Roughly 70-90% of the 2.8 million traumatic brain injuries (TBIs) that occur annually are mild (mTBI). Although a fairly benign injury, acutely, with clinical sign and symptom resolution occurring devoid of intervention in a few weeks, subtle neurophysiological deficits may persist beyond standard clinical recovery timelines of about one month. These deficits may be linked to dual-task and/or neuromuscular control dysfunction which may be the cause for the increased risk of subsequent lower extremity musculoskeletal injury (LE-MSI) post-concussion reported in youth, collegiate, and professional athletes; however, data are limited on females and community athletes. Further, beyond concussion, the long-term effects of repetitive head impacts (RHI) or impacts that do not result in clinical signs and symptoms of concussion remain a concern. Data are mixed on the long-term effects of RHI measured by age of first exposure (AFE) to contact/collision sports with some studies suggesting cognitive and emotional dysfunction in middle age and other studies suggesting no effect. Yet, these studies are limited to football and soccer playing middle aged males in addition to lacking objective measures of neurophysiological health and comparison groups. Further, the sex-specific response to RHI and the moderating effect of physical activity remain to be elucidated across the age spectrum. PURPOSE: The overall purpose of this dissertation was to identify the long-term effects of collision sport participation across individuals with varying levels of lifetime RHI exposure and physical activity levels. METHODS: For Aim 1, 1,037 (31.6 + 11.3 years, 40.9% female) community level rugby players completed an online survey via Qualtrics detailing demographics, sport history and AFE to sport, concussion and LE-MSI history, and patient reported outcomes (Brief-Symptom Inventory-18 (BSI-18), Short-Form 12 (SF-12 Physical and Mental Component Summary (PCS/MCS), and Satisfaction with Life Scale (SWLS)). Odds ratios (OR) by sex were performed to determine the odds of LE-MSI given history of concussion and a binary logistic regression to determine if there were sex differences in risk. Mann-Whitney U tests were performed to compare AFE groups (<12 and > 12 yr) for BSI-18, SF-12, and SWLS. Generalized linear models were performed to examine the association between AFE (continuous) and patient reported outcomes; predictors included age, career duration (i.e., cumulative years contact/collision sports), and concussion history (yes/no). For Aims 2 and 3, 113 adults were recruited representing four groups: 1) Former non-contact athletes/non-athletes who are not physically active (NON; N=28, 35.4 + 14.1 years); 2) Former non-contact athletes who are physically active (NCA; N=29, 33.9 + 10.8 years); 3) Former contact/collision sport athletes who participated in high risk for RHI sports (i.e., boxing, football, ice hockey, lacrosse, soccer, wrestling) who are physically active (HRS; N=29, 33.3 + 8.4 years); and 4) current and former rugby players, with a history of playing rugby after the age of 22 (e.g., prolonged RHI exposure into adulthood after the age at which most collision sport participation ceases) (RUG; N=27, 38.1 + 13.0 years). All participants completed an online questionnaire of demographics, injury history, sport history, and patient reported outcomes, in addition to common concussion assessments measuring multiple domains and systems, and single (ST) and dual-task (DT) inertial measurement unit instrumented gait and tandem gait. For Aim 2, a multiple regression was used to predict ST and DT gait outcomes in collision sport athletes from career duration. Groups were compared on all outcomes using Kruskal-Wallis test with a pairwise comparison procedure and Bonferroni correction for multiple corrections. Follow up analyses utilized covariates (concussion, learning disorder history, and career duration) in a one-way ANCOVA to compare groups on all outcomes. The relationship between ST gait speed and performance on clinical tests and dual task cost (DTC) gait speed and performance on clinical tests were analyzed using multiple Spearman’s rank-order correlations. For Aim 3, a linear regression was utilized to understand the effect of career duration and sex on gait outcomes (i.e., ST & DT gait speed, double support, stride length, and tandem gait, and their corresponding DTC outcomes). Further, a dummy variable was created to model the sex*career duration interaction and was also included in the model alongside sex and career duration in Block 1 using the “Enter” method. A second block with potential confounding factors (i.e., concussion history, LD/ADHD history, age, height) was also performed. RESULTS: For Aim 1, there was a significant association between diagnosed concussion and any LE-MSI(χ(1) = 13.055, p < 0.001, OR = 2.30 [95%CI: 1.45, 3.65]). There were no differences between sex for risk of LE-MSI (R2 = 0.024, p = 0.999). Whether analyzed continuously or dichotomously, younger AFE was not associated with worse patient-reported outcomes for either men or women. For Aim 2, career duration did not predict any of the gait outcomes (p>0.05). In adjusted models, there were no group differences on multiple outcomes. However, on 6/25 outcomes (SF-12 PCS, Apathy Evaluation Scale, SWLS, Montreal Cognitive Assessment (MOCA), Balance Error Scoring System (BESS), ST tandem gait) the NON group did significantly worse than the NCA group. The NON group also performed worse than RUG on BESS and ST gait speed. Spearman correlations revealed weak correlations between ST gait speed and SCAT5 Symptom Severity (rs = 0.282, p=0.002), Trails B (rs=-0.219, p=0.021), and SWLS (rs =0.282, p=0.002). As well as weak correlations between DTC gait speed and Trails A (rs = -0.216, p=0.022), Trails B (rs = -0.306, p<0.001), and MOCA (rs = 0.248, p=0.008). For Aim 3, there was no effect of sex on the relationship between career duration and gait outcomes (p>0.05). DISCUSSION: Collectively, these results suggest that contact/collision sport participation does not affect early- to mid-adulthood neurophysiological health in males and females. Further, career duration was not a sensitive enough measure to detect any group differences on assessment of neurophysiological health, warranting future research utilizing more precise measures of lifetime RHI exposure to determine if there truly is not an effect present. However, concussion history remains a significant predictor of quality of life and wellness in addition to its relationship with increased odds of LE-MSI. Lastly, there does not appear to be a significant effect of RHI on sex among measurements of ST and DT gait implying that both sexes are equally unaffected. These findings add to the growing body of evidence that contact/collision sport participation and RHI do not negatively affect mid-life neurophysiological health and function.
Description
Keywords
Brain health, Concussion, Neurological function, Repetitive head impacts, Rugby