Biomarkers of Neurobiologic Recovery in Adults With Sport-Related Concussion.

Importance: Sport-related concussion (SRC), a form of mild traumatic brain injury, is a prevalent occurrence in collision sports. There are no well-established approaches for tracking neurobiologic recovery after SRC. Objective: To examine the levels of serum glial fibrillary acidic protein (GFAP) and neurofilament light (NfL) in Australian football athletes who experience SRC. Design, Setting, and Participants: A cohort study recruiting from April 10, 2021, to September 17, 2022, was conducted through the Victorian Amateur Football Association, Melbourne, Australia. Participants included adult Australian football players with or without SRC. Data analysis was performed from May 26, 2023, to March 27, 2024. Exposure: Sport-related concussion, defined as at least 1 observable sign and/or 2 or more symptoms. Main Outcomes and Measures: Primary outcomes were serum GFAP and NfL levels at 24 hours, and 1, 2, 4, 6, 8, 12, and 26 weeks. Secondary outcomes were symptoms, cognitive performance, and return to training times. Results: Eighty-one individuals with SRC (median age, 22.8 [IQR, 21.3-26.0] years; 89% male) and 56 control individuals (median age, 24.6 [IQR, 22.4-27.3] years; 96% male) completed a total of 945 of 1057 eligible testing sessions. Compared with control participants, those with SRC exhibited higher GFAP levels at 24 hours (mean difference [MD] in natural log, pg/mL, 0.66 [95% CI, 0.50-0.82]) and 4 weeks (MD, 0.17 [95% CI, 0.02-0.32]), and NfL from 1 to 12 weeks (1-week MD, 0.31 [95% CI, 0.12-0.51]; 2-week MD, 0.38 [95% CI, 0.19-0.58]; 4-week MD, 0.31 [95% CI, 0.12-0.51]; 6-week MD, 0.27 [95% CI, 0.07-0.47]; 8-week MD, 0.36 [95% CI, 0.15-0.56]; and 12-week MD, 0.25 [95% CI, 0.04-0.46]). Growth mixture modeling identified 2 GFAP subgroups: extreme prolonged (16%) and moderate transient (84%). For NfL, 3 subgroups were identified: extreme prolonged (7%), moderate prolonged (15%), and minimal or no change (78%). Individuals with SRC who reported loss of consciousness (LOC) (33% of SRC cases) had higher GFAP at 24 hours (MD, 1.01 [95% CI, 0.77-1.24]), 1 week (MD, 0.27 [95% CI, 0.06-0.49]), 2 weeks (MD, 0.21 [95% CI, 0.004-0.42]) and 4 weeks (MD, 0.34 [95% CI, 0.13-0.55]), and higher NfL from 1 week to 12 weeks (1-week MD, 0.73 [95% CI, 0.42-1.03]; 2-week MD, 0.91 [95% CI, 0.61-1.21]; 4-week MD, 0.90 [95% CI, 0.59-1.20]; 6-week MD, 0.81 [95% CI, 0.50-1.13]; 8-week MD, 0.73 [95% CI, 0.42-1.04]; and 12-week MD, 0.54 [95% CI, 0.22-0.85]) compared with SRC participants without LOC. Return to training times were longer in the GFAP extreme compared with moderate subgroup (incident rate ratio [IRR], 1.99 [95% CI, 1.69-2.34]; NfL extreme (IRR, 3.24 [95% CI, 2.63-3.97]) and moderate (IRR, 1.43 [95% CI, 1.18-1.72]) subgroups compared with the minimal subgroup, and for individuals with LOC compared with those without LOC (IRR, 1.65 [95% CI, 1.41-1.93]). Conclusions and Relevance: In this cohort study, a subset of SRC cases, particularly those with LOC, showed heightened and prolonged increases in GFAP and NfL levels, that persisted for at least 4 weeks. These findings suggest that serial biomarker measurement could identify such cases, guiding return to play decisions based on neurobiologic recovery. While further investigation is warranted, the association between prolonged biomarker elevations and LOC may support the use of more conservative return to play timelines for athletes with this clinical feature.

Characterizing Factors Influencing Baseline Plasma Biomarkers for Sport-Related Concussion in Adolescents.

Abstract Developing objective measures to diagnose sport-related concussion (SRC) is a top priority, particularly in the pediatric context, given the vulnerability of the developing brain. While advances in SRC blood biomarkers are being made in adult populations, less data are available for adolescents. Clinical validation of blood biomarkers post-SRC will first require investigation in a healthy uninjured state. Further, rapid pubertal changes during adolescence may implicate possible interactions with circulating sex hormones and the menstrual cycle for females. This cross-sectional study aimed to characterize pre-injury plasma levels of glial fibrillary acidic protein (GFAP), neurofilament light (NF-L), ubiquitin C-terminal hydrolase-L1 (UCH-L1), total tau (T-tau), and phosphorylated tau-181 (P-tau-181), considering previous concussion, age, and sex in healthy adolescent sport participants. Possible associations with menstrual cycle phase and circulating sex hormone levels (i.e., progesterone, estradiol, testosterone) were also explored. Pre-injury blood samples were obtained from 149 healthy adolescents (48% female, ages 11-18) participating in a larger Surveillance in High Schools and Community Sports to Reduce Concussions and their Consequences (SHRed Concussions) multi-site longitudinal cohort study. Main outcomes were natural log (ln) transformed plasma GFAP, NF-L, UCH-L1, T-tau, and P-tau-181 concentrations, quantified on the Quanterix Simoa HD-X platform. Mixed-effects multi-variable linear regression was used to assess associations between biomarkers and self-reported previous concussion (yes/no), age (years), sex (male/female), objectively determined menstrual cycle phase (follicular/luteal), plasma progesterone, estradiol, and testosterone. Males had 19.8% lower UCH-L1 (ß = -0.221, 95% confidence interval [CI; -0.396, -0.046]), 18.9% lower GFAP (ß = -0.210, 95% CI [-0.352, -0.068]), and 21.8% higher P-tau-181 (ß = 0.197, 95% CI [0.048, 0.346]) compared with females, adjusting for age and previous concussion. GFAP decreased 9.5% with each 1-year increase in age, adjusting for previous concussion and sex (ß = -0.100, 95% CI [-0.152, -0.049]). No biomarkers were associated with a history of previous concussion. Exploratory investigations found no associations between biomarkers and menstrual cycle phase. Females displayed an age-adjusted negative association between T-tau and progesterone (ß = -0.010, 95% CI [-0.018, -0.002]), whereas males had a negative age-adjusted association between UCH-L1 and testosterone (ß = -0.020, 95% CI [-0.037, -0.002]). As such, age- and sex-specific reference intervals may be warranted for pediatric athlete populations prior to clinical validation of blood biomarkers for SRC. Additionally, hormonal associations highlight the need to consider puberty and development in adolescent studies. Overall, findings suggest these biomarkers are resilient to a history of previous concussion and menstrual cycle phase, supporting continued investigation in adolescent SRC.

Clinical and Blood Biomarker Trajectories after Concussion: New Insights from a Longitudinal Pilot Study of Professional Flat-Track Jockeys.

There is a recognized need for objective tools for detecting and tracking clinical and neuropathological recovery after sports-related concussion (SRC). Although computerized neurocognitive testing has been shown to be sensitive to cognitive deficits after SRC, and some blood biomarkers have shown promise as indicators of axonal and glial damage, the potential utility of these measures in isolation and combination for assisting SRC diagnosis and tracking recovery is not well understood. To provide new insights, we conducted a prospective study of 64 male and female professional flat-track jockeys (49 non-SRC, 15 SRC), with each jockey undergoing symptom evaluation, cognitive testing using the CogSport battery, and serum biomarker quantification of glial fibrillary acidic protein (GFAP), tau, and neurofilament light (NfL) using a Simoa HD-X Analyzer. Measures were performed at baseline (i.e., pre-injury), and 2 and 7 days and 1 and 12 months after SRC. Symptoms were most pronounced at 2 days and had largely resolved by either 7 days or 1 month. CogSport testing at 2 days revealed cognitive impairments relative to both non-concussed peers and their own pre-injury baselines, with SRC classification utility found at 2 days, and to a slightly lesser extent, at 7 days. Relatively prolonged changes in serum NfL were observed, with elevated levels and classification utility persisting beyond the resolution of SRC symptoms and cognitive deficits. Finally, SRC classification performance throughout the 1st month after SRC was optimized through the combination of cognitive testing and serum biomarkers. Considered together, these findings provide further evidence for a role of computerized cognitive testing and fluid biomarkers of neuropathology as objective measures to assist in the identification of SRC and the monitoring of clinical and neuropathological recovery.

The effect of omega-3 fatty acids on a biomarker of head trauma in NCAA football athletes: a multi-site, non-randomized study.

BACKGROUND: American-style football (ASF) athletes are at risk for cardiovascular disease (CVD) and exhibit elevated levels of serum neurofilament light (Nf-L), a biomarker of axonal injury that is associated with repetitive head impact exposure over the course of a season of competition. Supplementation with the w-3 fatty acid (FA) docosahexaenoic acid (DHA) attenuates serum Nf-L elevations and improves aspects of CVD, such as the omega-3 index (O3I). However, the effect of combining the w-3 FA eicosapentaenoic acid (EPA) and docosapentaenoic acid (DPA) with DHA on, specifically, serum Nf-L in ASF athletes is unknown. Therefore, this study assessed the effect of supplemental w-3 FA (EPA+DPA+DHA) on serum Nf-L, plasma w-3 FAs, the O3I, and surrogate markers of inflammation over the course of a season. METHODS: A multi-site, non-randomized design, utilizing two American football teams was employed. One team (n = 3 1) received supplementation with a highly bioavailablew-3 FA formulation (2000mg DHA, 560mg EPA, 320mg DPA, Mindset®, Struct Nutrition, Missoula, MT) during pre-season and throughout the regular season, while the second team served as the control (n = 35) and did not undergo supplementation. Blood was sampled at specific times throughout pre- and regular season coincident w ith changes in intensity, physical contact, and changes in the incidence and severity of head impacts. Group differences were determined via a mixed-model between-within subjects ANOVA. Effect sizes were calculated using Cohen's dfor all between-group differences. Significance was set a priori at p< .05. RESULTS: Compared to the control group, ASF athletes in the treatment group experienced large increases in plasma EPA (p < .001, d = 1.71) and DHA (p < .001, d = 2.10) which contributed to increases in the O3I (p < .001, d = 2.16) and the EPA:AA ratio (p = .001, d = 0.83) and a reduction in the w-6: w-3 ratio (p < .001, d = 1.80). w-3 FA supplementation attenuated elevations in Nf-L (p = .024). The control group experienced a significant increase in Nf-L compared to baseline at several measurement time points (T2, T3, and T4 [p range < .001 - .005, drange = 0.59-0.85]). CONCLUSIONS: These findings suggest a cardio- and neuroprotective effect of combined EPA+DPA+DHA w-3 FA supplementation in American-style football athletes. TRIAL REGISTRATION: This trial was registered with the ISRCTN registry ( ISRCTN90306741 ).

CSF and Blood Neurofilament Levels in Athletes Participating in Physical Contact Sports: A Systematic Review.

OBJECTIVE: To evaluate whether participating in physical contact sports is associated with a release of neurofilaments and whether such release is related to future clinical neurologic and/or psychiatric impairment. METHODS: We performed a systematic review of the PubMed, MEDLINE, and Cochrane Library databases using a combination of the search terms neurofilament(s)/intermediate filament and sport(s)/athletes. Original studies, written in English, reporting on neurofilaments in CSF and/or serum/plasma of contact sport athletes were included. This review was conducted following the Preferred Reporting Items for Systematic Review and Analyses guidelines. RESULTS: Eighteen studies in 8 different contact sports (i.e., boxing, American football, ice hockey, soccer, mixed martial arts, lacrosse, rugby, and wrestling) matched our criteria. Elevated light chain neurofilament (NfL) levels were described in 13/18 cohorts. Most compelling evidence was present in boxing and American football, where exposure-related increases were appreciable at the intraindividual level (up to 4.1- and 2.0-fold, respectively) in well-defined groups. Differences in exposure severity (including previous cumulative effects), sampling/measurement time points (with regard to expected peak values), and definitions of the baseline setting are considered as main contributors to the variability in findings. No studies were encountered that have investigated the relationship with the targeted clinical end points; therefore no NfL cutoffs exist that are associated with a poor outcome. CONCLUSION: NfL release can be seen, as a potential marker of neuronal brain damage, in participants of physical contact sports, particularly boxing and American football. The exact significance regarding the risk for future clinical impairment remains to be elucidated.

Assessment of Blood Biomarker Profile After Acute Concussion During Combative Training Among US Military Cadets: A Prospective Study From the NCAA and US Department of Defense CARE Consortium.

Importance: Validation of protein biomarkers for concussion diagnosis and management in military combative training is important, as these injuries occur outside of traditional health care settings and are generally difficult to diagnose. Objective: To investigate acute blood protein levels in military cadets after combative training-associated concussions. Design, Setting, and Participants: This multicenter prospective case-control study was part of a larger cohort study conducted by the National Collegiate Athletic Association and the US Department of Defense Concussion Assessment Research and Education (CARE) Consortium from February 20, 2015, to May 31, 2018. The study was performed among cadets from 2 CARE Consortium Advanced Research Core sites: the US Military Academy at West Point and the US Air Force Academy. Cadets who incurred concussions during combative training (concussion group) were compared with cadets who participated in the same combative training exercises but did not incur concussions (contact-control group). Clinical measures and blood sample collection occurred at baseline, the acute postinjury point (<6 hours), the 24- to 48-hour postinjury point, the asymptomatic postinjury point (defined as the point at which the cadet reported being asymptomatic and began the return-to-activity protocol), and 7 days after return to activity. Biomarker levels and estimated mean differences in biomarker levels were natural log (ln) transformed to decrease the skewness of their distributions. Data were collected from August 1, 2016, to May 31, 2018, and analyses were conducted from March 1, 2019, to January 14, 2020. Exposure: Concussion incurred during combative training. Main Outcomes and Measures: Proteins examined included glial fibrillary acidic protein, ubiquitin C-terminal hydrolase-L1, neurofilament light chain, and tau. Quantification was conducted using a multiplex assay (Simoa; Quanterix Corp). Clinical measures included the Sport Concussion Assessment Tool-Third Edition symptom severity evaluation, the Standardized Assessment of Concussion, the Balance Error Scoring System, and the 18-item Brief Symptom Inventory. Results: Among 103 military service academy cadets, 67 cadets incurred concussions during combative training, and 36 matched cadets who engaged in the same training exercises did not incur concussions. The mean (SD) age of cadets in the concussion group was 18.6 (1.3) years, and 40 cadets (59.7%) were male. The mean (SD) age of matched cadets in the contact-control group was 19.5 (1.3) years, and 25 cadets (69.4%) were male. Compared with cadets in the contact-control group, those in the concussion group had significant increases in glial fibrillary acidic protein (mean difference in ln values, 0.34; 95% CI, 0.18-0.50; P < .001) and ubiquitin C-terminal hydrolase-L1 (mean difference in ln values, 0.97; 95% CI, 0.44-1.50; P < .001) levels at the acute postinjury point. The glial fibrillary acidic protein level remained high in the concussion group compared with the contact-control group at the 24- to 48-hour postinjury point (mean difference in ln values, 0.22; 95% CI, 0.06-0.38; P = .007) and the asymptomatic postinjury point (mean difference in ln values, 0.21; 95% CI, 0.05-0.36; P = .01). The area under the curve for all biomarkers combined, which was used to differentiate cadets in the concussion and contact-control groups, was 0.80 (95% CI, 0.68-0.93; P < .001) at the acute postinjury point. Conclusions and Relevance: This study's findings indicate that blood biomarkers have potential for use as research tools to better understand the pathobiological changes associated with concussion and to assist with injury identification and recovery from combative training-associated concussions among military service academy cadets. These results extend the previous findings of studies of collegiate athletes with sport-associated concussions.

Preliminary Report: Localized Cerebral Blood Flow Mediates the Relationship between Progesterone and Perceived Stress Symptoms among Female Collegiate Club Athletes after Mild Traumatic Brain Injury.

Female athletes are under-studied in the field of concussion research, despite evidence of higher injury prevalence and longer recovery time. Hormonal fluctuations caused by the natural menstrual cycle (MC) or hormonal contraceptive (HC) use impact both post-injury symptoms and neuroimaging findings, but the relationships among hormone, symptoms, and brain-based measures have not been jointly considered in concussion studies. In this preliminary study, we compared cerebral blood flow (CBF) measured with arterial spin labeling between concussed female club athletes 3-10 days after mild traumatic brain injury (mTBI) and demographic, HC/MC matched controls (CON). We tested whether CBF statistically mediates the relationship between progesterone serum levels and post-injury symptoms, which may support a hypothesis for progesterone's role in neuroprotection. We found a significant three-way relationship among progesterone, CBF, and perceived stress score (PSS) in the left middle temporal gyrus for the mTBI group. Higher progesterone was associated with lower (more normative) PSS, as well as higher (more normative) CBF. CBF mediates 100% of the relationship between progesterone and PSS (Sobel p value = 0.017). These findings support a hypothesis for progesterone having a neuroprotective role after concussion and highlight the importance of controlling for the effects of sex hormones in future concussion studies.

An investigation of plasma interleukin-6 in sport-related concussion.

BACKGROUND: Increasing evidence suggests inflammation is an important component of concussion pathophysiology. However, its etiology, restitution, and potential clinical repercussions remain unknown. The purpose of the current study was to compare the blood concentrations of interleukin (IL) -6, a prominent inflammatory cytokine, between healthy athletes and athletes with a sport-related concussion (SRC), while addressing the potential confounds of sex, recent physical activity, and the interacting effect of concussion history. METHOD: A prospective, observational cohort study was conducted on athletes at a single academic institute participating across 13 interuniversity sports. Follow-up of 96 athletes who agreed to provide a blood sample was completed: 41 athletes with a physician diagnosed SRC, and 55 healthy athletes. Ella™, the high sensitivity immunoassay system by ProteinSimple was used to measure peripheral plasma concentrations of IL-6 within the first week (median = 4 days, range = 2-7) following injury. A resampled ordinary least squares regression was used to evaluate the relationship between IL-6 concentrations and concussion status, while partial least squares regression was used to evaluate the relationship between IL-6 and both symptom burden and time to clinical recovery. RESULTS: Regression analysis identified a negative relationship between plasma IL-6 concentrations and the interaction between an acute SRC and a history of concussion (ß = -0.29, p = 0.029). IL-6 did not differ between healthy athletes and those with an acute SRC independent of concussion history, and was not correlated with either recovery time or symptom burden in athletes with SRC. CONCLUSION: Perturbations to circulating IL-6 concentrations, a key inflammatory cytokine, may be more pronounced following SRC in athletes who have a history of concussion. These results add to a growing body of evidence supporting the involvement of inflammation at all phases of recovery following SRC, and potentially support a concomitant effect of prior concussion on acute SRC pathophysiology.

A Prospective Study of Acute Blood-Based Biomarkers for Sport-Related Concussion.

OBJECTIVE: Prospectively characterize changes in serum proteins following sport-related concussion and determine whether candidate biomarkers discriminate concussed athletes from controls and are associated with duration of symptoms following concussion. METHODS: High school and collegiate athletes were enrolled between 2015 and 2018. Blood was collected at preinjury baseline and within 6 hours (early acute) and at 24 to 48 hours (late acute) following concussion in football players (n = 106), matched uninjured football players (n = 84), and non-contact-sport athletes (n = 50). Glial fibrillary acidic protein, ubiquitin c-terminal hydrolase-L1, S100 calcium binding protein B, alpha-II-spectrin breakdown product 150, interleukin 6, interleukin 1 receptor antagonist, and c-reactive protein were measured in serum. Linear models assessed changes in protein concentrations over time. Receiver operating curves quantified the discrimination of concussed athletes from controls. A Cox proportional hazard model determined whether proteins were associated with symptom recovery. RESULTS: All proteins except glial fibrillary acidic protein and c-reactive protein were significantly elevated at the early acute phase postinjury relative to baseline and both control groups and discriminated concussed athletes from controls with areas under the curve of 0.68 to 0.84. The candidate biomarkers also significantly improved the discrimination of concussed athletes from noncontact controls compared to symptom severity alone. Glial fibrillary acidic protein was elevated postinjury relative to baseline in concussed athletes with a loss of consciousness or amnesia. Finally, early acute levels of interleukin 1 receptor antagonist were associated with the number of days to symptom recovery. INTERPRETATION: Brain injury and inflammatory proteins show promise as objective diagnostic biomarkers for sport-related concussion, and inflammatory markers may provide prognostic value. ANN NEUROL 2020;87:907-920.

Acute Effects of Sport-Related Concussion on Serum Glial Fibrillary Acidic Protein, Ubiquitin C-Terminal Hydrolase L1, Total Tau, and Neurofilament Light Measured by a Multiplex Assay.

We prospectively evaluated serum concentrations of glial fibrillary acidic protein (GFAP), ubiquitin c-terminal hydrolase L1 (UCH-L1), total tau (T-Tau), and neurofilament light (NF-L) from collegiate athletes at baseline and acutely after sport-related concussion (SRC) using the Quanterix Neurology 4Plex "B" (N4PB) multiplex assay. Uninjured controls were matched on age, sex, race, sport, and concussion history. Clinical outcomes included acute symptom severity, balance, rapid automated naming, computerized cognitive testing, and recovery duration. Baseline (n = 110; median [interquartile range] age = 19 [18-20] years, 54% male, 61% white/Caucasian) and post-SRC (n = 36; median [interquartile range] age = 19 [18-20] years, 50% male, 61% white/Caucasian) blood samples were analyzed. We observed post-SRC elevations from baseline for GFAP (p = 0.001, d = 1.7), T-Tau (p = 0.004, d = 1.3), and NF-L (p = 0.010, d = 1.1). GFAP (area under the curve [AUC] = 0.958, 95% confidence interval [CI] 0.927-0.989, p < 0.001) and NF-L (AUC = 0.904, 95% CI 0.851-0.957, p < 0.001) accurately discriminated SRC from control cases. There were no associations between biomarker concentrations and clinical measurements post-SRC or recovery duration. These findings suggest that, using the multiplex assay, GFAP, T-Tau, and NF-L elevate from baseline acutely after SRC, and both GFAP and NF-L excellently distinguished concussed from control cases. Serum biomarker changes do not necessarily correspond with clinical measurements or recovery duration.

Peripheral blood neuroendocrine hormones are associated with clinical indices of sport-related concussion.

The purpose of this study was to evaluate the relationship between neuroendocrine hormones and clinical recovery following sport-related concussion (SRC). Ninety-five athletes (n = 56 male, n = 39 female) from a cohort of 11 interuniversity sport teams at a single institution provided blood samples; twenty six athletes with SRC were recruited 2-7 days post-injury, and 69 uninjured athletes recruited prior to the start of their competitive season. Concentrations of seven neuroendocrine hormones were quantitated in either plasma or serum by solid-phase chemiluminescent immunoassay. The Sport Concussion Assessment Tool version 5 (SCAT-5) was used to evaluate symptoms at the time of blood sampling in all athletes. Multivariate partial least squares (PLS) analyses were used to evaluate the relationship between blood hormone concentrations and both (1) time to physician medical clearance and (2) initial symptom burden. A negative relationship was observed between time to medical clearance and both dehydroepiandrosterone sulfate (DHEA-S) and progesterone; a positive relationship was found between time to medical clearance and prolactin. Cognitive, somatic, fatigue and emotion symptom clusters were associated with distinct neuroendocrine signatures. Perturbations to the neuroendocrine system in athletes following SRC may contribute to initial symptom burden and longer recovery times.

Acute myocardial infarction in a young elite cyclist: a missed opportunity.

A 27-year-old elite-level professional cyclist presented to the emergency department with a 6-hour history of chest pain and vomiting after prematurely aborting a competitive event. ECG demonstrated anterior ST segment elevation myocardial infarction, and blood tests revealed a grossly elevated high-sensitivity troponin T. Emergent coronary angiography confirmed the presence of a thrombus in the mid-left anterior descending artery with possible spontaneous coronary artery dissection. The patient recovered well following balloon angioplasty and thrombus aspiration, despite delayed recognition, invasive investigation and intervention.

Exploratory study of sport-related concussion effects on peripheral micro-RNA expression.

OBJECTIVE: Explore changes in micro-RNA (miRNA) expression in blood after sport-related concussion (SRC) in collegiate athletes. METHODS: Twenty-seven collegiate athletes (~41% male, ~75% white, age 18.8 ± 0.8 years) provided both baseline and post-SRC blood samples. Serum was analyzed for expression of miR-153-3p (n = 27), miR-223-3p (n = 23), miR-26a-5p (n = 26), miR-423-3p (n = 23), and miR-let-7a-5p (n = 23) at both time points via quantitative polymerase chain reaction (qPCR). Nonparametric analyses were used to compare miRNA expression changes between baseline and SRC and to evaluate associations with clinical outcomes (symptom severity, cognition, balance, and oculomotor function, and clinical recovery time). RESULTS: Participants manifested a significant increase in miRNA expression following SRC for miR153-3p (Z = -2.180, p = .029, 59% of the participants increased post-SRC), miR223-3p (Z = -1.998, p = .046, 70% increased), and miR-let-7a-5p (Z = -2.190, p = .029, 65% increased). There were no statistically significant associations between changes in miRNA expression and clinical test scores, acute symptom severity, or clinical recovery time. CONCLUSION: MiR-153-3p, miR-223-3p, and miR-let-7a-5p were significantly upregulated acutely following SRC in male and female collegiate athletes compared to baseline levels, though several athletes demonstrated no change or a decrease in expression. The biological mechanisms and functional implications of the increased expression of these circulating miRNA are unclear and require more research, as does their relevance to clinical outcomes.

Elevated Creatine Kinase and Lactic Acid Dehydrogenase and Decreased Osteocalcin and Uncarboxylated Osteocalcin are Associated with Bone Stress Injuries in Young Female Athletes.

Stress fractures are a limitation for athletes not only in sports performance but in activities of daily living. Thus, preventing them is crucial. In female athletes, a triad of symptoms including low energy availability, functional hypothalamic amenorrhea and osteoporosis are considered risk factors for stress injuries, but biomarkers predictive of these outcomes are not available. Here, we evaluated 56 female university athletes and found that 13 had a history of stress bone injuries. Logistic regression analysis demonstrated that dysmenorrhea including amenorrhea, but not reduced food intake or body weight loss, was significantly associated with stress injuries. When we subdivided subjects into stress fracture and non-fracture groups, we found that serum levels of creatine kinase (CK) and lactic acid dehydrogenase (LDH) were significantly higher in the fracture group, while osteocalcin and uncarboxylated osteocalcin (ucOC), which are bone forming parameters, significantly decreased. Low vitamin D levels are associated with stress fractures, but serum vitamin D levels were higher in fracture compared to non-fracture subjects. We followed up 32 subjects for one year, and three exhibited new stress injuries during that period. A history of stress fracture history is significantly associated with experiencing a new stress fracture. We also found that subjects with new fracture performed significantly greater exercise activity than did non-fracture subjects. Taken together, our data indicate that increased serum CK and LDH and decreased serum osteocalcin and ucOC are biomarkers of stress injuries, and evaluating these markers along with dysmenorrhea, stress fracture history or high sports activity could predict future stress fractures in female athletes.

Concussion BASICS II: Baseline serum biomarkers, head impact exposure, and clinical measures.

OBJECTIVE: To examine the effect of concussion history and cumulative exposure to collision sports on baseline serum biomarker concentrations, as well as associations between biomarker concentrations and clinical assessments. METHODS: In this observational cohort study, ß-amyloid peptide 42 (Aß42), total tau, S100 calcium binding protein B (S100B), ubiquitin carboxy-terminal hydrolyzing enzyme L1 (UCH-L1), glial fibrillary acidic protein, microtubule associated protein 2, and 2',3'-cyclic-nucleotide 3'-phosphodiesterase serum concentrations were measured in 415 (61% male, 40% white, aged 19.0 ± 1.2 years) nonconcussed collegiate athletes without recent exposure to head impacts. Regression analyses were used to evaluate the relationship between self-reported history of concussion(s), cumulative years playing collision sports, clinical assessments, and baseline biomarker concentrations. Football-specific analyses were performed using a modified Cumulative Head Impact Index. Clinical assessments included symptom, cognitive, balance, and oculomotor tests. RESULTS: Athletes with a greater number of concussions had a higher baseline Aß42 concentration only (ρ = 0.140, p = 0.005, small effect size). No biomarker concentrations correlated with cumulative exposure to collision sports. Race status fully mediated the correlations of S100B, UCH-L1, and Aß42 with cognitive scores. Football exposure, specifically, was not associated with serum biomarker concentrations or clinical assessment scores based on the modified Cumulative Head Impact Index. CONCLUSION: Concussion-related serum biomarkers showed no consistent association with concussion history, cumulative exposure to collision sports, or clinical assessments in a sample of healthy collegiate athletes. Serum Aß42 concentrations could increase following multiple previous concussions. Considering race status is essential when investigating links between biomarkers and cognition. The biomarkers studied may not detect residual effects of concussion or repetitive head impact exposure in otherwise asymptomatic collegiate athletes without recent exposure to head impacts. Much more research is needed for identifying reliable and valid blood biomarkers of brain trauma history.

Concussion BASICS III: Serum biomarker changes following sport-related concussion.

OBJECTIVE: To evaluate changes in serum biomarker concentrations (ß-amyloid peptide 42 [Aß42], total tau, ubiquitin carboxy-terminal hydrolyzing enzyme L1, S100 calcium binding protein B [S100B], glial fibrillary acidic protein [GFAP], microtubule associated protein 2 [MAP2], and 2',3'-cyclic-nucleotide 3'-phosphodiesterase [CNPase]) after sport-related concussion (SRC) in a sample of collegiate athletes. Associations with clinical outcomes were also investigated. METHODS: Participants in this case-control study included 36 athletes (50% male, 61% white, aged 19.7 ± 1.0 years) with SRC. Twenty-nine also had baseline blood drawn, allowing for within-patient analyses of concentration changes. Between-group analyses incorporated 86 demographically matched controls (51% male, 63% white, aged 19.6 ± 1.1 years). Biomarker sensitivity/specificity for SRC vs controls and relative to standardized normative cutoffs was evaluated (receiver operating characteristics). We also analyzed associations between post-SRC clinical outcomes and both biomarker change from baseline and post-SRC concentrations. RESULTS: The majority of blood samples had concentrations of GFAP, MAP2, and CNPase below limits of quantification. Within-patient analyses indicated elevated S100B after SRC (p = 0.003, 67% of patients elevated), especially for blood samples collected <4 hours post-SRC (88% of patients). Significant between-group differences were limited to blood draws <4 hours post-SRC: Aß42 (81% of SRC > control median, area under the curve [AUC] = 0.75 [95% confidence interval 0.59-0.91]), total tau (75% SRC > control, AUC = 0.74 [0.56-0.79]), and S100B (88% SRC > control; AUC [specific to white race] = 0.82 [0.72-0.93]). Using standardized normative cutoffs (z > 1.0), specificity ranged from 79.1% to 89.3% while sensitivity was <70%. Biomarkers were not associated with clinical outcomes. CONCLUSION: For SRC, diagnostic accuracy of serum biomarkers appears best if blood is collected within a few hours. Accurate blood marker identification of SRC appears somewhat dependent on the "healthy" comparison. Additional research must evaluate whether physiologic changes in the absence of clinical changes, or vice versa, are relevant for concurrent or future neurologic health. CLASSIFICATION OF EVIDENCE: This study provides Class III evidence that certain serum biomarkers are elevated from baseline and higher than demographically matched controls after sport-related concussion.

Effects of match play and training on circulating S100B concentration in professional rugby players.

OBJECTIVES: Examine the effects of match play and a season of training on serum S100B concentration in male professional rugby players. To assess the influence of contact play, values were compared with age- and fitness-matched athletes not involved in a contact sport. METHODS: Over a 2-year period, blood samples were collected from 38 players in pre-season, end of season, and post-matches (within 2 h). A control group of rowers (n = 15) was assessed pre- and post-training. RESULTS: S100B concentration changed significantly over a season (χ2(2) = 17.636, p < 0.0005); post-match values were significantly increased from baseline (early season: Z = -3.670, p < 0.0005; late season: Z = -3.408, p = 0.001). There were no significant differences in S100B concentrations between pre-seasons (Z = -1.601, p = 0.109), or between end of season and subsequent pre-season (Z = -0.330, p = 0.741). While comparable at baseline, samples taken from rugby players post-match were significantly increased compared with samples taken from rowers post-exercise (U = 47.0, p < 0.0005). CONCLUSION: Exercise has a significant effect on circulating S100B in elite male athletes, with levels following rugby matches significantly higher than following non-contact sport. This elevation in S100B is temporary, with a return to baseline values after periods without play.

No change in plasma tau and serum neurofilament light concentrations in adolescent athletes following sport-related concussion.

Sport-related concussion (SRC), a mild form of traumatic brain injury (TBI), is a common injury in contact sports. Health care professionals rely on subjective criteria (e.g., symptoms), as there is no objective marker for identification of athletes with SRC. Blood-based biomarkers have shown promise as diagnostic and prognostic tools following TBI and SRC. In the present study, we examined plasma tau and serum NF-L, two biomarkers for neuronal/axonal injury, concentrations at preseason and following SRC in contact sport athletes (n = 11) using ultrasensitive single molecule array (Simoa) assays. Preseason baseline samples were collected, and post-concussion samples were obtained at 6- and 14-days following injury. We found no difference between baseline, 6-day and 14-day post-concussion concentrations of tau (p = 0.14) or NF-L (p = 0.53). Further, no difference was found between preseason baseline and all post-SRC samples for tau (p = 0.22) or NF-L (p = 0.98). The total number of symptoms reported on the Standardized Assessment of Concussion- 3rd Edition (SCAT3) and associated symptom severity scores increased from preseason to 6-days post-SRC but returned to baseline values at 14-days (p = 0.02 and p = 0.003, respectively). These results suggest that the severity of neuronal injury in this cohort of contact sport athletes with clinical uncomplicated SRC was too low to be detected by tau and NF-L measurements in blood samples obtained at 6- and 14-days post-injury.