Recurrent Concussion Research Articles

Mental health symptom burden in elite ice hockey players and its association with self-reported concussive events

BackgroundSome studies suggest that elite athletes experience adverse mental health symptoms at rates commensurate with the general population, despite the well-established buffering effects of exercise. Within contact sports, such as ice-hockey, recurrent concussions may be a source of this discrepancy. We compared the point prevalence of various mental health outcomes with other athlete and general population samples, as well as investigated their relationship with concussive events.MethodsWe surveyed 648 active ice hockey players from the top two men’s tiers and the top women’s tier in Swedish elite ice hockey on lifetime concussive events, hazardous alcohol use, problematic social media use, depression, anxiety, and burnout.ResultsHazardous alcohol use was more prevalent among male ice hockey players (29.5% AUDIT-C ≥ 6) compared to other athlete and general population samples, while other mental health symptoms were less common. Female ice hockey players reported higher hazardous alcohol consumption (36.4% AUDIT-C ≥ 4) than another athlete sample and more burnout (19.1%) than the general population. After adjusting for covariates, athletes with 3+ concussive events had 2.1 times the odds of elevated depressive symptoms and 3.5 times the odds of elevated burnout symptoms compared to those with no concussion history. Treating lifetime concussive events as a continuous predictor revealed positive correlations with all outcomes except for hazardous alcohol use.ConclusionsMental health outcome rates among active elite ice hockey athletes differ from those of other athlete and general population samples, whilst concussive events may be particularly linked to elevated symptoms of depression and burnout.

The Significance of Off-Season Tailor-Made Baseline Measurements in the Assessment of Post-Concussion in University Athletes.

This study aimed to investigate the significance of baseline measurements for amateur team athletes playing contact and collision team sports with a specific focus on the Sports Concussion Assessment Tool (SCAT) to improve concussion management. Symptoms of sports-related concussions (SRCs) can be diverse and long-lasting and include cognitive impairment, sleep disturbances, and vestibular dysfunction. Therefore, comprehensive baseline data are essential to preventing recurrent concussions and secondary injuries. This study was conducted during the 2023 off-season and evaluated the baseline condition of 65 male university rugby players using the SCAT5, which includes self-reported symptoms, and the modified Balance Error Scoring System (mBESS). The athletes were assessed for the presence or absence of SRC, and the mean values were compared using the Mann-Whitney U test. Among the participants, 35.38% (23/65) reported symptoms, with an average of 1.5 ± 2.8 symptoms per player and an average symptom score of 2.66 ± 5.93. In the mBESS, no errors were observed in the tandem stance test; however, 72.31% (47/65) made errors in the single-leg stance test on the non-dominant foot, with an average of 1.7 ± 1.5 errors. Many athletes self-reported symptoms and balance errors, even during asymptomatic periods before experiencing concussion, indicating unresolved issues. In the injury history survey, the baseline evaluations and injury histories of the participants classified into the SRC and non-SRC groups were compared. In the mBESS single-leg stance test (non-dominant foot), 84.21% (32/38) of the SRC group participants made errors, with an average score of 2.13 ± 1.52, whereas 55.55% (15/27) of the non-SRC group participants made errors, with an average score of 1.15 ± 1.35, showing a significant difference (p = 0.007). Additionally, significant differences were observed in the average number of ankle sprains (p = 0.027) and fractures (p = 0.048) between patients with and without a history of SRC. These findings indicate that athletes may have underlying issues even during normal periods before concussion. Moreover, the results highlighted the impact of previous concussions on motor control and injury risk. This underscores the importance of preseason baseline measurements using the SCAT to identify at-risk athletes and implement preventive measures. These findings align with the recommendations of the 6th International Conference on Concussion in Sport and suggest further refinement of concussion assessment tools.

Epidemiology of Subsequent and Recurrent Injuries in Rugby: A Systematic Review

Objective To review and collate epidemiological data on recurrent and subsequent injuries in male rugby and identify risk factors such as injury type. Methods Four databases were searched from January 1, 1974 through October 1, 2020. Keywords were:((“Football”[Mesh]) OR (rugby)) AND ((recurrent injury) OR (subsequent injury)) in PubMed, (‘rugby’/exp OR rugby) AND (recurrent AND (‘injury’/exp OR injury) OR subsequent) AND (‘injury’/exp OR injury) in Embase, rugby AND (subsequent injury OR recurrent injury) in CINAHL Plus, and TOPIC: (rugby) AND TOPIC: (subsequent injur* OR recurrent injur*) in Web of Science. Inclusion Criteria:(i) population consisted of male rugby players; (ii) used “time-loss” as an injury definition; (iii) included extractable data on both subsequent injury count and recurrent injury count; (iv) written in English. 6/1242 studies met criteria for inclusion. Quality was assessed using STROBE guidelines. Results Studies using “missed-match” as a definition of time-loss showed no difference in incidence of subsequent versus recurrent injuries. Studies using “24-hour time-loss” as the definition of injury reported 7,724 (71%) subsequent injuries (95% CI: 0.71–0.72) and 1,434 (14%) recurrent injuries (95% CI: 0.13–0.15). In pediatric players, 98 (23%) were subsequent (95% CI: 0.19–0.27) and 21 (5%) were recurrent (95% CI: 0.03–0.08). When specifying concussions as an index injury, 119 (40%; 95% CI: 0.34–0.46) subsequent injuries other than a concussion were reported with 27 (9%; 95% CI: 0.06–0.13) recurrent concussions. Conclusion Injury definition and type of index injury plays a significant role when considering subsequent and recurrent injury incidence in male rugby players. Further investigation regarding incidence of secondary injury after specific types of index injury is warranted.

Return-to-Play With R2Play: Protocol for Evaluating Cross-Site Feasibility, Face Validity, and Content Validity of a Multidomain Concussion Assessment Tool for Youth

Context: Clinical concussion assessments do not typically simulate the speed or complexity of sport. Performance changes arising from combined physical, cognitive, and sensory demands of sport may thus remain undetected during rehabilitation. We developed R2Play, a multidomain return-to-play assessment tool for youth with concussions. R2Play involves levels and conditions that vary in physical, cognitive, and sensory load to simulate the multidomain demands of sport. Objectives: To explore cross-site feasibility, face validity, and content validity of R2Play by integrating quantitative and qualitative data. Methods: Convergent mixed-methods feasibility study. Five sites will each recruit 5 clinicians (total nc = 25) and 10 youth sport participants (ages 10–25 y) with a history of concussion in the previous year (total ny = 50). Feasibility will be evaluated using quantitative criteria for acceptability, demand, implementation, practicality, and integration, and qualitative investigated data from content analysis of postassessment interviews with youth and clinician participants. Face validity will be investigated in postassessment interviews. Content validity will be established through (1) changes in performance metrics (time to completion, errors, and heart rate) across R2Play levels, (2) youth-perceived physical and cognitive exertion for each level, and (3) overall clinician perceptions determined through postassessment interviews. Qualitative and quantitative data will be merged through joint display to identify areas of convergence, divergence, and complementarity, and to establish meta-inferences about feasibility, face validity, and content validity. Discussion: This study aims to demonstrate the face and content validity of R2Play, and its feasibility for cross-site implementation. Findings will guide further iteration of R2Play and establish the foundation for a larger multicenter validation study to establish the psychometric properties of R2Play. This work represents an important first step toward the implementation of an ecologically valid multidomain assessment tool designed to support a safe and efficient return-to-play after concussion, ultimately reducing the risk of recurrent concussion and subsequent injury.

Treatment of Recurrent Concussion-RETRACTION.

Treatment of Recurrent Concussion-RETRACTION.

Return to Sports Following Sports-Related Concussion in Collision Sports: An Expert Consensus Statement Using the Modified Delphi Technique

The purpose of this study was to perform a Delphi consensus for return to sports (RTS) following sports related concussion (SRC). Open-ended questions in rounds 1 and 2 were answered. The results of the first two rounds were used to develop a Likert style questionnaire for round 3. If agreement at round 3 was <80% for an item, if panel members were outside consensus or there were >30% neither agree/disagree responses, the results were carried forward into round 4. The level of agreement and consensus was defined as 90%. Individualized graduated RTS protocols should be used. A normal clinical, ocular and balance examination with no more headaches and asymptomatic exertional test allows RTS. Earlier RTS can be considered if athletes are symptom free. SCAT5 and VOMS are recognized as useful tools to assist in decision making. Ultimately RTS is a clinical decision. Baseline assessments should be performed at both collegiate and professional level and a combination of neurocognitive and clinical tests should be used. A specific number of recurrent concussions for season - or career ending decisions could not be determined but will affect decision making for RTS. Consensus was achieved for 10 of the 25 RTS criteria: early RTS can be considered earlier than 48-72 hours if athletes are completely symptom-free with no headaches, a normal clinical, ocular and balance examination. A graduated RTS should be utilized but should be individualized. Only two of the nine assessment tools were considered to be useful: SCAT5 and VOMS. RTS is mainly a clinical decision. Only 31% of the baseline assessment items achieved consensus: baseline assessments should be performed at collegiate and professional levels using a combination of neurocognitive and clinical tests. The panel disagreed on the number of recurrent concussions that should be season- or career ending.

Higher hazard of concussion combined with recurrent concussion in female youth ice hockey compared with males: An opportunity for concussion prevention

Higher hazard of concussion combined with recurrent concussion in female youth ice hockey compared with males: An opportunity for concussion prevention

Effects of repetitive head trauma on symptomatology of subsequent sport-related concussion.

Adolescent participation in athletics continues to grow, leading to an increasing incidence of sports-related concussion (SRC). The current literature suggests that a greater number of prior concussions positively correlates with a greater number of total symptoms, but the specific concussion-related symptoms are not as well defined. The current study investigated the effects of prior recurrent head injury on the symptom profiles of student-athletes after another suspected concussion. A multicenter database consisting of 25,815 Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT) results was filtered for student-athletes aged 12-22 years old who competed in 21 different sports. Patients were separated into 2 cohorts: athletes reporting a single prior concussion (SRC1) and athletes reporting 2 or more prior concussions (SRC2+). Comparisons were assessed for differences in 22 symptoms and 4 symptom clusters at baseline, first postinjury test (PI1), and second postinjury test (PI2) by using univariate and multivariate analyses. No differences were seen between SRC1 (n = 2253) and SRC2+ (n = 976) at baseline. At PI1, the SRC2+ group (n = 286) had lower severity of headaches (p = 0.04) but increased nervousness (p = 0.042), irritability (p = 0.028), sadness (p = 0.028), visual problems (p = 0.04), and neuropsychiatric symptoms (p = 0.009) compared with SRC1 (n = 529). Multivariate analysis revealed decreased headache severity with increased prior concussion (β = -0.27,95% CI -0.45 to -0.09, p = 0.003). Multivariate analysis at PI2 demonstrated the SRC2+ cohort (n = 130) had increased cognitive (β = 1.22, 95% CI 0.27-2.18, p = 0.012), sleep (β = 0.63, 95% CI 0.17-1.08, p = 0.007), and neuropsychiatric (β = 0.67,95% CI 0.14-1.2,0.014) symptoms compared with SRC1 (n = 292). At longitudinal follow-up, patients with a history of recurrent concussions reported greater symptom burden in cognitive, sleep, and neuropsychiatric symptom clusters but not migraine symptoms. This is an important distinction because migraine symptoms are often more easily distinguishable to patients, parents, and physicians. Careful assessment of specific symptoms should be considered in patients with a history of recurrent head injury prior to return to play.

The Effectiveness of Physical Therapy Interventions for Athletes Post-Concussion: A Systematic Review.

Sports-related concussions are the most common cause of head injury in adolescents and young adults. Typical treatment methods for this injury include cognitive and physical rest. Evidence suggests that physical activity and physical therapy interventions can be beneficial to decrease post-concussion symptoms. The aim of this systematic review was to investigate the effectiveness of physical therapy interventions for adolescent and young adult athletes post-concussion. Systematic Review. The following databases were utilized for the search: PubMed, CINAHL, Proquest, MEDLINE, SPORTDiscus, and SCOPUS. The search strategy focused on athletes, concussions, and physical therapy interventions. Data extraction from each article included: Authors, subjects, gender, mean age, age range, specific sport, acute or chronic concussion, first or recurrent concussion, treatments for intervention and control group, and outcomes measured. Eight studies met the inclusion criteria. Six of the eight articles scored seven or higher on the PEDro Scale. Physical therapy intervention(s), such as an aerobic intervention or a multimodal approach, show improvements in time to recovery and reduction of post-concussion symptoms in patients who have had a concussion. Physical activity and physical therapy as early as a couple days following injury, is beneficial at decreasing post-concussion symptoms, allows for earlier return to play, and/or shorter days to recovery, and is considered safe for treating post-concussion symptoms. This systematic review demonstrates that physical therapy interventions including aerobic exercise and multimodal approaches have been found to be beneficial in treating adolescent and young adult athletes post-concussion. Utilizing aerobic or multimodal interventions for this population allows for a quicker symptom recovery and return to sport than traditional treatment of physical and cognitive rest. Future research should investigate the superior intervention for adolescents and young adults with post-concussion syndrome and determine if a single treatment or a multimodal approach is more beneficial.

Systematic Review and Meta-Analysis of Sex-Based Differences in Recurrent Concussion Incidence Across Sports

BACKGROUND: Disparities in concussion incidence exist on the basis of sex. This meta-analysis aimed to summarize the evidence for recurrent concussion incidence between male and female athletes across various sports. METHODS: Systematic review and meta-analysis. Data Sources - PubMed, EMBASE, and Cochrane Library databases. Eligibility Criteria for Selecting Studies - Studies written in English containing sex comparisons of recurrent concussion data published between January 2000 and June 2021 were included. RESULTS: A total of 1,509 records were identified, of which 114 studies were assessed for eligibility with full-text review. Six studies were ultimately included. Women were found to have more recurrent concussions than men across all sex-comparable sports, which included soccer, basketball, and baseball/softball [RR=2.16 (95% CI: 1.09-4.30)]. More specifically, women were found to have more recurrent concussions in soccer [RR=3.01 (95% CI: 2.08-4.35)] and basketball [RR=2.68 (95% CI: 1.39-5.17)], but inconclusive results were seen for baseball/softball [RR=2.54 (95% CI: 0.54-11.94)]. CONCLUSION: Recurrent concussion rates are greater in sex-comparable women’s sports than in men’s sports. Not all sports had sufficient evidence for inclusion in the meta-analysis. There are sex differences in recurrent concussion incidence in soccer and basketball.

Mechanisms of Sports Concussion in Taekwondo: A Systematic Video Analysis of Seven Cases.

Sports-related traumatic brain injuries are the most common injury in adolescents and young adults due to recurrent concussion experiences and head shock. Therefore, this study was designed to describe player characteristics and situational factors associated with concussions in the World Taekwondo Championships using systematic video analysis. Athlete injury data were collected using a web-based injury surveillance system at the World Taekwondo Championships organized by World Taekwondo from 2017 to 2019. Seven video footage were independently analyzed by four analysts using a modified Heads-Up Checklist. Descriptive statistical analysis was used. The incidence of concussion was 3.21 per 1000 games. Most players with concussions were shorter than their opponents, and most concussions were caused by a roundhouse kick on the front of the face. Regarding the acceleration direction of the head after the impact, transverse and multiplane directions were the most common. Most players with a concussion have used a closed stance and did not use blocking techniques during the defense. The rate of concussions caused by penalties was 42.9%. Based on our findings, no other injury mechanisms, except for direct blows to the head, were observed. Therefore, education on the risk and symptoms of concussion, the appropriate management and blocking techniques should be emphasized in TKD-S to reduce incidence of concussion.

World Federation of Athletic Training and Therapy World Congress 2022 Peer-Reviewed Track Abstracts, May 5–7, 2022, Winnipeg, Manitoba, Canada

World Federation of Athletic Training and Therapy World Congress 2022 Peer-Reviewed Track Abstracts, May 5–7, 2022, Winnipeg, Manitoba, Canada

472 Effects of Recurrent Mild Traumatic Brain Injuries on Incidence, Severity, and Recovery of Concussion in Young Student-Athletes

INTRODUCTION: Currently, it is known that athletes who sustain recurrent concussions are at an increased risk for long-term neurological consequences. Moreover, in the short term, athletes with a history of concussions are significantly more likely to sustain future concussions. Although the increased incidence of mTBI among athletes with a history of concussions has been well documented, there is less consensus about how recurrent concussions affect the severity and recovery of the next head trauma. METHODS: Data from 11 563 ImPACT baseline evaluations of US student-athletes aged 12 to 22 years were separated into 2 cohorts: subjects reporting 2 or more previous concussions (PC; n = 976 baseline evaluations) at baseline and a control group reporting zero previous concussions (CT; n = 7743 baseline evaluations). Subjects reporting 1 prior concussion were excluded. Differences in SND incidence, severity, and recovery between the 2 cohorts were assessed using chi-squared tests, t tests, survival analyses, and multivariate regressions. RESULTS: The PC cohort had a higher incidence of head injury leading to ImPACT (436.7 per 1000 person-years vs 194.4 per 1000 person-years, P &lt; .0001) and a higher incidence of SND (140.4 vs 71.8, P &lt; .0001) than controls. However, the Severity Index (SI) demonstrated that SND severity was lower in the PC group (7.55 vs 8.59, P = .04). Adjusted analyses similarly demonstrated that the PC cohort had increased SND incidence (odds ratio = 1.93; 95% CI, 1.61 to 2.31; P &lt; .0001), decreased SI (β = −1.37; 95% CI, −2.40 to −0.34; P = .009), and equivalent recovery (hazard ratio = 0.98; 95% CI, 0.76 to 1.72; P = .90). CONCLUSION: Participants with a history of concussion have a higher incidence of SND but present with lower severity SND, which may be a result of increased concussion education or symptom awareness. Recurrent concussion has no significant impact on acute neurocognitive recovery. Together, these results provide evidence against the supposition that a history of concussion increases the severity of future SND.

A role of Na+, K+ -ATPase in spatial memory deficits and inflammatory/oxidative stress after recurrent concussion in adolescent rats

Sports-related concussions are particularly common during adolescence, and there is insufficient knowledge about how recurrent concussions in this phase of life alter the metabolism of essential structures for memory in adulthood. In this sense, our experimental data revealed that seven recurrent concussions (RC) in 35-day-old rats decreased short-term and long-term memory in the object recognition test (ORT) 30 days after injury. The RC protocol did not alter motor and anxious behavior and the immunoreactivity of brain-derived neurotrophic factor (BDNF) in the cerebral cortex. Recurrent concussions induced the inflammatory/oxidative stress characterized here by increased glial fibrillary acidic protein (GFAP), interleukin 1β (IL 1β), 4-hydroxynonenal (4 HNE), protein carbonyl immunoreactivity, and 2',7'-dichlorofluorescein diacetate oxidation (DCFH) levels and lower total antioxidant capacity (TAC). Inhibited Na+,K+-ATPase activity (specifically isoform α2/3) followed by Km (Michaelis-Menten constant) for increased ATP levels and decreased immunodetection of alpha subunit of this enzyme, suggesting that cognitive impairment after RC is caused by the inability of surviving neurons to maintain ionic gradients in selected targets to inflammatory/oxidative damage, such as Na,K-ATPase activity.

Spotlight on the September 21 Issue

#### Notable in Neurology This Week This issue features an article that examines the effects of recurrent concussions on cerebral blood flow and the white matter microstructure of midline brain structures; another compares the effectiveness of initial treatment options for children with infantile spasms. A featured Special Article examines the use, abuse, and ethical implications of social media in …

Concussion history in rugby union players is associated with depressed cerebrovascular reactivity and cognition.

Recurrent contact and concussion in rugby union remains a significant public health concern given the potential increased risk of neurodegeneration in later life. This study determined to what extent prior-recurrent contact impacts molecular-hemodynamic biomarkers underpinning cognition in current professional rugby union players with a history of concussion. Measurements were performed in 20 professional rugby union players with an average of 16 (interquartile range [IQR] 13-19) years playing history reporting 3 (IQR 1-4) concussions. They were compared to 17 sex-age-physical activity-and education-matched non-contact controls with no prior history of self-reported concussion. Venous blood was assayed directly for the ascorbate free radical (A•- electron paramagnetic resonance spectroscopy) nitric oxide metabolites (NO reductive ozone-based chemiluminescence) and select biomarkers of neurovascular unit integrity (NVU chemiluminescence/ELISA). Middle cerebral artery blood flow velocity (MCAv doppler ultrasound) was employed to determine basal perfusion and cerebrovascular reactivity (CVR) to hyper/hypocapnia ( ). Cognition was assessed by neuropsychometric testing. Elevated systemic oxidative-nitrosative stress was confirmed in the players through increased A•- (p<0.001) and suppression of NO bioavailability (p<0.001). This was accompanied by a lower CVR range ( ; p=0.045) elevation in neurofilament light-chain (p=0.010) and frontotemporal impairments in immediate-memory (p=0.001) delayed-recall (p=0.048) and fine-motor coordination (p<0.001). Accelerated cognitive decline subsequent to prior-recurrent contact and concussion history is associated with a free radical-mediated suppression of CVR and neuronal injury providing important mechanistic insight that may help better inform clinical management.

Recurrent neural network-based acute concussion classifier using raw resting state EEG data

Concussion is a global health concern. Despite its high prevalence, a sound understanding of the mechanisms underlying this type of diffuse brain injury remains elusive. It is, however, well established that concussions cause significant functional deficits; that children and youths are disproportionately affected and have longer recovery time than adults; and that individuals suffering from a concussion are more prone to experience additional concussions, with each successive injury increasing the risk of long term neurological and mental health complications. Currently, the most significant challenge in concussion management is the lack of objective, clinically- accepted, brain-based approaches for determining whether an athlete has suffered a concussion. Here, we report on our efforts to address this challenge. Specifically, we introduce a deep learning long short-term memory (LSTM)-based recurrent neural network that is able to distinguish between non-concussed and acute post-concussed adolescent athletes using only short (i.e. 90 s long) samples of resting state EEG data as input. The athletes were neither required to perform a specific task nor expected to respond to a stimulus during data collection. The acquired EEG data were neither filtered, cleaned of artefacts, nor subjected to explicit feature extraction. The LSTM network was trained and validated using data from 27 male, adolescent athletes with sports related concussion, benchmarked against 35 non-concussed adolescent athletes. During rigorous testing, the classifier consistently identified concussions with an accuracy of > 90% and achieved an ensemble median Area Under the Receiver Operating Characteristic Curve (ROC/AUC) equal to 0.971. This is the first instance of a high-performing classifier that relies only on easy-to-acquire resting state, raw EEG data. Our concussion classifier represents a promising first step towards the development of an easy-to-use, objective, brain-based, automatic classification of concussion at an individual level.

Association Between Design Elements of Concussion Laws and Reporting of Sports-Related Concussions Among US High School Athletes, 2009-2017.

Studies that evaluate the effectiveness of concussion laws often use only a single variable (ie, presence of the law), failing to account for law complexity. We examined the association between multiple design elements of state concussion laws and rates of sports-related concussion reporting among US high school athletes. We derived 3 design elements of concussion laws from the 2009-2017 LawAtlas database: (1) strength of law, (2) number of law revisions, and (3) speed of law adoption. We examined the association between these design elements and rates of new and recurrent sports-related concussion reporting from the 2009-2010 through 2016-2017 academic years in a nationally representative sample of high school athletes participating in High School Report Information Online, an online data collection tool. A total of 7064 sports-related concussions (6332 [89.6%] new and 732 [10.4%] recurrent concussions) were reported during the study period, with an overall rate of 39.7 sports-related concussions per 100 000 athletic exposures (eg, game or practice). Rates of new concussion reporting were higher among high schools in states with medium- or high-strength concussion laws than in states with low-strength concussion laws and in states with at least 1 concussion law revision than in states with no concussion law revisions. Rates of recurrent concussion reporting were lower among high schools in states with ≥2 concussion law revisions than in states with <2 concussion law revisions. Early law adoption was associated with higher rates of new and recurrent concussion reporting, and late law adoption was associated with lower rates of new and recurrent concussion reporting. Our findings may help inform legislators of the public health effect of concussion laws.

Effects of Recurrent Mild Traumatic Brain Injuries on Incidence, Severity, and Recovery of Concussion in Young Student-Athletes.

To examine the effects of recurrent concussions on the incidence, severity, and recovery of significant neurocognitive dysfunction (SND) in young athletes. Various US youth sports organizations that utilize Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT) for baseline and postinjury concussion testing. Data from 11 563 ImPACT baseline evaluations of US student-athletes aged 12 to 22 years were separated into 2 cohorts: subjects reporting 2 or more previous concussions (PC; n = 976 baseline evaluations) at baseline and a control group reporting zero previous concussions (CT; n = 7743 baseline evaluations). Subjects reporting 1 prior concussion were excluded. Retrospective cohort. Differences in SND incidence, severity, and recovery between the 2 cohorts were assessed using chi-squared tests, t tests, survival analyses, and multivariate regressions. The PC cohort had a higher incidence of head injury leading to ImPACT (436.7 per 1000 person-years vs 194.4 per 1000 person-years, P < .0001) and a higher incidence of SND (140.4 vs 71.8, P < .0001) than controls. However, the Severity Index (SI) demonstrated that SND severity was lower in the PC group (7.55 vs 8.59, P = .04). Adjusted analyses similarly demonstrated that the PC cohort had increased SND incidence (odds ratio = 1.93; 95% CI, 1.61 to 2.31; P < .0001), decreased SI (β = -1.37; 95% CI, -2.40 to -0.34; P = .009), and equivalent recovery (hazard ratio = 0.98; 95% CI, 0.76 to 1.72; P = .90). Participants with a history of concussion have a higher incidence of SND but present with lower severity SND, which may be a result of increased concussion education or symptom awareness. Recurrent concussion has no significant impact on acute neurocognitive recovery. Together, these results provide evidence against the supposition that a history of concussion increases the severity of future SND.

Saliva microRNA Biomarkers of Cumulative Concussion.

Recurrent concussions increase risk for persistent post-concussion symptoms, and may lead to chronic neurocognitive deficits. Little is known about the molecular pathways that contribute to persistent concussion symptoms. We hypothesized that salivary measurement of microribonucleic acids (miRNAs), a class of epitranscriptional molecules implicated in concussion pathophysiology, would provide insights about the molecular cascade resulting from recurrent concussions. This hypothesis was tested in a case-control study involving 13 former professional football athletes with a history of recurrent concussion, and 18 age/sex-matched peers. Molecules of interest were further validated in a cross-sectional study of 310 younger individuals with a history of no concussion (n = 230), a single concussion (n = 56), or recurrent concussions (n = 24). There was no difference in neurocognitive performance between the former professional athletes and their peers, or among younger individuals with varying concussion exposures. However, younger individuals without prior concussion outperformed peers with prior concussion on three balance assessments. Twenty salivary miRNAs differed (adj. p < 0.05) between former professional athletes and their peers. Two of these (miR-28-3p and miR-339-3p) demonstrated relationships (p < 0.05) with the number of prior concussions reported by younger individuals. miR-28-3p and miR-339-5p may play a role in the pathophysiologic mechanism involved in cumulative concussion effects.