Breton M. Asken

Epidemiology of Sport-Related Concussion in an NCAA Division I Football Bowl Subdivision Sample

Background: Concussions are common in football, and knowledge of their incidence rates across settings is needed to develop strategies to decrease occurrence. Purpose: To examine sports-related concussion rates in a National Collegiate Athletic Association (NCAA) Division I Football Bowl Subdivision sample based on the activity setting where injuries occurred, during which type of play, and when relative to the 2010 NCAA concussion management policy. Study Design: Descriptive epidemiology study. Methods: Medical records from January 2006 to January 2015 for an NCAA Division I Football Bowl Subdivision program were analyzed. Concussion rates (per 1000 athlete-exposures [AEs]) were compared among the following settings: spring practice, preseason training camp, regular season high-contact practice, regular season low-contact practice, bowl game practice, and game competition. Play-type analyses examined incidence rates during offensive, defensive, and special teams plays. Changes in concussion rate coinciding with the 2010 NCAA concussion management policy were also studied. Results: Of the 452 unique players on the roster during the 9-year study period, 118 (26.1%) were diagnosed with a concussion. The concussion rate during games was significantly higher than all practices combined (P < .001). However, when game rate (4.46 per 1000 AEs) was compared with preseason training camp alone (3.81 per 1000 AEs), there was no significant difference (P = .433). The concussion rate during special teams plays was significantly higher than that during offensive (P < .001) or defensive plays (P < .001). The concussion rate in the 4 seasons (2010-2014) after the 2010 NCAA concussion management policy was initiated was significantly higher than the 4 seasons (2006-2009) preceding the policy (P = .036). Conclusion: Study results show that (1) based on activity type, games and preseason training camp present the greatest risk of sustaining a concussion; (2) based on play type, special teams plays pose the greatest risk of sustaining a concussion; and (3) the 2010 NCAA concussion management policy coincided with a significant increase in recognition of concussion.

Research Gaps and Controversies in Chronic Traumatic Encephalopathy: A Review

Importance Scientific and lay interest in negative outcomes associated with exposure to repetitive brain trauma (RBT) continues to strengthen. Concerns about the association between RBT and dementia began more than a century ago, but have resurfaced in the last decade with the more recently described chronic traumatic encephalopathy (CTE). Chronic traumatic encephalopathy is a tauopathy associated with RBT that has become inextricably linked to conversations about sport-related concussion and mild traumatic brain injury. Accordingly, specific populations such as collision sport athletes and certain military personnel are of particular interest owing to their unique exposure to RBT. The gaps and controversies in our understanding of the epidemiologic factors, mechanism, and clinicopathological correlates of CTE reflect the current reliance on postmortem case series investigations. This review discusses the state of the science of CTE and raises considerations for researching and interpreting cognitive changes in members of at-risk populations. Observations The recent development of pathological diagnostic criteria for CTE represented an important step for differentiating CTE from other neurodegenerative diseases. By comparison, defining the clinical syndrome(s) associated with CTE and the necessary and sufficient symptoms needed for its diagnosis lags behind. The absence of validated in vivo biomarkers of pathological characteristics of CTE and longitudinal tracking with neuropsychological evaluation remains a significant hurdle. Attribution of candidate symptoms in retired athletes to CTE is complicated by the presence of multiple premorbid and comorbid factors affecting cognitive reserve that influence normal or expected cognitive functioning. This is a critical issue in appropriately defining reference groups for normative comparisons. Conclusions and Relevance Available data, while limited and complicated by selection bias, indicate that exposure to RBT represents the greatest risk factor for CTE pathological features, although clinicopathological correlates and the nature of onset and progression of symptoms are largely unknown. Considering aspects of cognitive reserve is likely essential for both interpreting cognitive outcomes associated with CTE and for developing preventive treatment programs. Research on CTE would benefit greatly from incorporating principles established within other areas of neurodegenerative disease and the nuances of clinicopathological considerations.

Factors Influencing Clinical Correlates of Chronic Traumatic Encephalopathy (CTE): a Review.

Chronic traumatic encephalopathy (CTE) is a neuropathologically defined disease reportedly linked to a history of repetitive brain trauma. As such, retired collision sport athletes are likely at heightened risk for developing CTE. Researchers have described distinct pathological features of CTE as well a wide range of clinical symptom presentations, recently termed traumatic encephalopathy syndrome (TES). These clinical symptoms are highly variable, non-specific to individuals described as having CTE pathology in case reports, and are often associated with many other factors. This review describes the cognitive, emotional, and behavioral changes associated with 1) developmental and demographic factors, 2) neurodevelopmental disorders, 3) normal aging, 4) adjusting to retirement, 5) drug and alcohol abuse, 6) surgeries and anesthesia, and 7) sleep difficulties, as well as the relationship between these factors and risk for developing dementia-related neurodegenerative disease. We discuss why some professional athletes may be particularly susceptible to many of these effects and the importance of choosing appropriate controls groups when designing research protocols. We conclude that these factors should be considered as modifiers predominantly of the clinical outcomes associated with repetitive brain trauma within a broader biopsychosocial framework when interpreting and attributing symptom development, though also note potential effects on neuropathological outcomes. Importantly, this could have significant treatment implications for improving quality of life.

Diffusion tensor imaging (DTI) findings in adult civilian, military, and sport-related mild traumatic brain injury (mTBI): a systematic critical review

This review seeks to summarize diffusion tensor imaging (DTI) studies that have evaluated structural changes attributed to the mechanisms of mild traumatic brain injury (mTBI) in adult civilian, military, and athlete populations. Articles from 2002 to 2016 were retrieved from PubMed/MEDLINE, EBSCOhost, and Google Scholar, using a Boolean search string containing the following terms: “diffusion tensor imaging”, “diffusion imaging”, “DTI”, “white matter”, “concussion”, “mild traumatic brain injury”, “mTBI”, “traumatic brain injury”, and “TBI”. We added studies not identified by this method that were found via manually-searched reference lists. We identified 86 eligible studies from English-language journals using, adult, human samples. Studies were evaluated based on duration between injury and DTI assessment, categorized as acute, subacute/chronic, remote mTBI, and repetitive brain trauma considerations. Since changes in brain structure after mTBI can also be affected by other co-occurring medical and demographic factors, we also briefly review DTI studies that have addressed socioeconomic status factors (SES), major depressive disorder (MDD), and attention-deficit hyperactivity disorder (ADHD). The review describes population-specific risks and the complications of clinical versus pathophysiological outcomes of mTBI. We had anticipated that the distinct population groups (civilian, military, and athlete) would require separate consideration, and various aspects of the study characteristics supported this. In general, study results suggested widespread but inconsistent differences in white matter diffusion metrics (primarily fractional anisotropy [FA], mean diffusivity [MD], radial diffusivity [RD], and axial diffusivity [AD]) following mTBI/concussion. Inspection of study designs and results revealed potential explanations for discrepant DTI findings, such as control group variability, analytic techniques, the manner in which regional differences were reported, and the presence or absence of persistent functional disturbances. DTI research in adult mTBI would benefit from more standardized imaging and analytic approaches. We also found significant overlap in white matter abnormalities reported in mTBI with those commonly affected by SES or the presence of MDD and ADHD. We conclude that DTI is sensitive to a wide range of group differences in diffusion metrics, but that it currently lacks the specificity necessary for meaningful clinical application. Properly controlled longitudinal studies with consistent and standardized functional outcomes are needed before establishing the utility of DTI in the clinical management of mTBI and concussion.

Descriptive Characteristics of Concussions in National Football League Games, 2010-2011 to 2013-2014:

Background: Despite a high reported incidence rate of concussion, little is known about the on-field characteristics of injurious head impacts in National Football League (NFL) games. Purpose: To characterize on-field features (location, player position, and time during game) and biomechanical features (anticipation status, closing distance, impact location and type) associated with concussions in NFL games over a 4-season period (2010-2011 to 2013-2014). Study Design: Descriptive epidemiology study. Methods: We analyzed video of a subset of reported, in-game concussions for the 2010-2011 to 2013-2014 seasons. These videos represented a sample of injuries that were diagnosed and reported on the same day and that could be clearly associated with an in-game collision as captured on video. We determined anticipation status, closing distance, impact location on the injured player’s helmet, and impact type (helmet-to-helmet, helmet-to-body, or helmet-to-ground). Associations between these variables were analyzed by use of descriptive statistics and tests of association. Results: A total of 871 diagnosed concussions were reported as occurring during NFL preseason, regular season, and postseason games for the 2010-2011, 2011-2012, 2012-2013, and 2013-2014 seasons. A total of 1324 games were played during this period, giving a concussion incidence rate of 0.658 per game (95% CI, 0.61-0.70). From the video-reviewed subset (n = 429; 49.3%), the majority of injurious impacts occurred with good anticipation (57.3%) and <10 yards of closing distance (59.0%). An association was found between anticipation status and play type ( χ 3 2 = 27.398, P < .001), largely because injuries occurring on pass plays were more likely to be poorly anticipated than injuries during run plays (43.0% vs 21.4%; χ 1 2 = 14.78, P < .001). Kick returns had the greatest proportion of well-anticipated impacts (78%) and the greatest proportion of impacts with ≥10 yards of closing distance (80%). The type of impact was approximately equally divided between helmet-to-helmet, helmet-to-body, and helmet-to-ground types. The impact location was broadly distributed over the helmet of the injured player. Conclusion: In-game concussions in the NFL occurred through a diverse variety of mechanisms, surprisingly tended to be well-anticipated, and, also surprisingly, occurred with <10 yards of closing distance. The impacts causing concussion were broadly distributed over the helmet. More concussions occurred during the second half of game play, but we do not have evidence to explain this finding.

Glymphatic system disruption as a mediator of brain trauma and chronic traumatic encephalopathy

Graphical abstract Figure. No Caption available. HighlightsA model of the mediating effect of disrupted sleep on GS functioning and CTE pathology is proposed.Sleep disruption affects the ability of the GS to clear metabolic waste.Protein waste accumulates in perivascular spaces in CTE, which is one pathway used by the GS.Chronic disruption of the GS following brain trauma may increase the risk for developing CTE‐like pathology and clinical symptomatology. ABSTRACT Traumatic brain injury (TBI) is an increasingly important issue among veterans, athletes and the general public. Difficulties with sleep onset and maintenance are among the most commonly reported symptoms following injury, and sleep debt is associated with increased accumulation of beta amyloid (A&bgr;) and phosphorylated tau (p‐tau) in the interstitial space. Recent research into the glymphatic system, a lymphatic‐like metabolic clearance mechanism in the central nervous system (CNS) which relies on cerebrospinal fluid (CSF), interstitial fluid (ISF), and astrocytic processes, shows that clearance is potentiated during sleep. This system is damaged in the acute phase following mTBI, in part due to re‐localization of aquaporin‐4 channels away from astrocytic end feet, resulting in reduced potential for waste removal. Long‐term consequences of chronic dysfunction within this system in the context of repetitive brain trauma and insomnia have not been established, but potentially provide one link in the explanatory chain connecting repetitive TBI with later neurodegeneration. Current research has shown p‐tau deposition in perivascular spaces and along interstitial pathways in chronic traumatic encephalopathy (CTE), pathways related to glymphatic flow; these are the main channels by which metabolic waste is cleared. This review addresses possible links between mTBI‐related damage to glymphatic functioning and physiological changes found in CTE, and proposes a model for the mediating role of sleep disruption in increasing the risk for developing CTE‐related pathology and subsequent clinical symptoms following repetitive brain trauma.

Concussion-like symptom reporting in non-concussed adolescent athletes

Abstract Objective: The primary goals of this study were (1) to report rates of concussion-like symptoms in healthy adolescent student athletes assessed using the Sport Concussion Assessment Tool, 3rd edition (SCAT3) at baseline, (2) to examine rates of psychiatric diagnoses in this population, and (3) to evaluate effects of baseline symptoms on SCAT3 cognitive and balance performance.Methods: 349 adolescent student athletes (245 male) were administered the SCAT3 during pre-participation physical examinations. We described the prevalence rate of student athletes meeting criteria for International Classification of Diseases, 10th revision, post-concussional syndrome (ICD-10 PCS) diagnosis at baseline, and evaluated associations between symptom reporting and demographic/medical history factors using chi-square tests. Rates of self-reported psychiatric diagnosis were compared to general population estimates with one-sample binomial tests. We also compared SCAT3 cognitive and balance performance between adolescents with and without baseline ICD-10 PCS symptoms.Results: Overall, 20.3% of participants met ICD-10 PCS criteria at baseline. Rates were similar across sexes and age groups. We found no statistical association with medical history factors. The proportion of student athletes reporting a history of psychiatric diagnosis (5.2%) was significantly lower than general population estimates (14.0%; p < .001), and this effect was consistent across sexes and age groups. SCAT3 cognitive and balance performance did not differ based on baseline symptom reporting.Conclusions: Healthy adolescent student athletes frequently report concussion-like symptoms at baseline. Clinicians should factor pre-injury symptomatology and medical history into concussion management when determining symptom etiology throughout the course of recovery.

Injury cascades in TBI-related neurodegeneration

ABSTRACT Traumatic brain injury (TBI) is a widely recognized risk factor for neurodegenerative disease. The purpose of this review is to provide an update on the state of the science related to injury cascades in TBI-related neurodegeneration. Acute and chronic pathological outcomes of TBI are similar to those seen in several neurodegenerative conditions, suggesting common linking pathways. Initial research described severe TBI patients with post-mortem identification of abnormal proteins, such as amyloid deposits. History of mild TBI (mTBI) is less consistently associated with heightened risk of neurodegenerative outcomes, but specific populations with complicated medical histories and comorbidities may be more susceptible. Our understanding of a pathological signature associated with repetitive mTBI and/or subclinical brain trauma advanced significantly over the past decade, and is now commonly referred to as chronic traumatic encephalopathy. We discuss hypotheses linking TBI to neurodegenerative disease, and the importance of considering factors like injury severity, timing of injury (early life versus older age), injury frequency, and repetitive subclinical brain trauma when extrapolating results from current literature to certain populations. We describe the challenges to obtaining the data necessary for accurate epidemiological research and determination of true risk magnitude, and note the importance of developing treatment-based approaches to risk mitigation.

Concussion-like symptom reporting in non-concussed collegiate athletes

Objective Non-concussed individuals may report a variety of concussion-like symptoms even in the absence of a diagnosed brain injury. Previous studies described concussion-like symptom reporting in adolescent athletes. This study provides complementary data on concussion-like symptoms in collegiate athletes. Methods We analyzed baseline symptom scales from 738 collegiate athletes (452 men and 286 women) who completed either the Sport Concussion Assessment Tool, 3 Symptom Evaluation (S3SE; n = 377) or the Post-Concussion Scale (PCS; n = 361) and determined if subjects met criteria for diagnosis of International Classification of Diseases 10th Revision (ICD-10) postconcussional syndrome. Symptoms were grouped as somatic, cognitive, emotional, or sleep-related. We analyzed associations with medical history factors using chi-square analyses, and examined recovery time of a subset of concussed athletes based on baseline symptomatology (n = 117) with independent samples t-test. Results Across all athletes, 120 (16.3%) reported baseline symptoms meeting criteria for ICD-10 postconcussional syndrome. Women were 1.7 times more likely to meet these criteria (21.7% vs. 12.8%, p = .002). Athletes completing the S3SE were 1.5 times more likely to meet criteria than those completing the PCS (p = .011). Previously diagnosed psychiatric disorder was significantly associated with emotional domain symptom reporting, and attention deficit-hyperactivity disorder diagnosis was associated with cognitive domain symptom reporting. On average, athletes meeting ICD-10 postconcussional syndrome criteria at baseline experienced longer recovery from concussion (t[115] = 2.35, p = .020). Conclusions Non-concussed collegiate athletes report concussion-like symptoms at a clinically significant rate. Pre-injury medical history and reporting rates of concussion-like symptoms may explain variance in post-concussion symptom expression. Measured incidence of baseline postconcussional syndrome may, in part, depend on the symptom report measure that is used.

Socioeconomic Status and Race Outperform Concussion History and Sport Participation in Predicting Collegiate Athlete Baseline Neurocognitive Scores

OBJECTIVES The purpose of this study was to assess the contribution of socioeconomic status (SES) and other multivariate predictors to baseline neurocognitive functioning in collegiate athletes. METHODS Data were obtained from the Concussion Assessment, Research and Education (CARE) Consortium. Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT) baseline assessments for 403 University of Florida student-athletes (202 males; age range: 18-23) from the 2014-2015 and 2015-2016 seasons were analyzed. ImPACT composite scores were consolidated into one memory and one speed composite score. Hierarchical linear regressions were used for analyses. RESULTS In the overall sample, history of learning disability (β=-0.164; p=.001) and attention deficit-hyperactivity disorder (β=-0.102; p=.038) significantly predicted worse memory and speed performance, respectively. Older age predicted better speed performance (β=.176; p<.001). Black/African American race predicted worse memory (β=-0.113; p=.026) and speed performance (β=-.242; p<.001). In football players, higher maternal SES predicted better memory performance (β=0.308; p=.007); older age predicted better speed performance (β=0.346; p=.001); while Black/African American race predicted worse speed performance (β=-0.397; p<.001). CONCLUSIONS Baseline memory and speed scores are significantly influenced by history of neurodevelopmental disorder, age, and race. In football players, specifically, maternal SES independently predicted baseline memory scores, but concussion history and years exposed to sport were not predictive. SES, race, and medical history beyond exposure to brain injury or subclinical brain trauma are important factors when interpreting variability in cognitive scores among collegiate athletes. Additionally, sport-specific differences in the proportional representation of various demographic variables (e.g., SES and race) may also be an important consideration within the broader biopsychosocial attributional model. (JINS, 2018, 24, 1-10).