Neurofilament light and tau in serum after head-impact exposure in soccer

Functional connectivity changes in neurodegenerative biomarker-positive athletes with repeated concussions

Multimodal biomarkers may identify former contact sports athletes with repeated concussions and at risk for dementia. Our study aims to investigate whether biomarker evidence of neurodegeneration in former professional athletes with repetitive concussions (ExPro) is associated with worse cognition and mood/behavior, brain atrophy, and altered functional connectivity. Forty-one contact sports athletes with repeated concussions were divided into neurodegenerative biomarker-positive (n = 16) and biomarker-negative (n = 25) groups based on positivity of serum neurofilament light-chain. Six healthy controls (negative for biomarkers) with no history of concussions were also analyzed. We calculated cognitive and mood/behavior composite scores from neuropsychological assessments. Gray matter volume maps and functional connectivity of the default mode, salience, and frontoparietal networks were compared between groups using ANCOVAs, controlling for age, and total intracranial volume. The association between the connectivity networks and sports characteristics was analyzed by multiple regression analysis in all ExPro. Participants presented normal-range mean performance in executive function, memory, and mood/behavior tests. The ExPro groups did not differ in professional years played, age at first participation in contact sports, and number of concussions. There were no differences in gray matter volume between groups. The neurodegenerative biomarker-positive group had lower connectivity in the default mode network (DMN) compared to the healthy controls and the neurodegenerative biomarker-negative group. DMN disconnection was associated with increased number of concussions in all ExPro. Biomarkers of neurodegeneration may be useful to detect athletes that are still cognitively normal, but with functional connectivity alterations after concussions and at risk of dementia.

Heading in football: a systematic review of descriptors, definitions, and reporting methods used in heading incidence studies

The primary objective of this systematic review was to describe the number and type of heading descriptors used in all published studies which report on heading incidence in football. The secondary objective was to detail the data collection and reporting methods used in the included studies to present heading incidence data. Eligible studies were identified through searches of five electronic databases: Ovid MEDLINE, CINAHL, EMBASE, SPORTDiscus, and Web of Science, using a combination of free-text keywords (inception to 12th September 2023). Manual searching of reference lists and retrieved systematic reviews was also performed. A descriptive overview and synthesis of the results is presented. From 1620 potentially eligible studies, 71 studies were included, with the following key findings: 1) only 61% of studies defined a header with even fewer (23%) providing an operational definition of a header within the methods; 2) important study and player demographic data including year and country were often not reported; 3) reported heading descriptors and their coding options varied greatly; 4) visual identification of headers was essential when inertial measurement units were used to collect heading incidence data; and 5) there was a lack of standardisation in the reporting methods used in heading incidence studies making comparison between studies challenging. To address these findings, the development of a standardised, internationally supported, operational definition of a header and related heading descriptors should be prioritised. Further recommendations include the development of minimum reporting criteria for heading incidence research.

The Use of Biofluid Markers to Evaluate the Consequences of Sport-Related Subconcussive Head Impact Exposure: A Scoping Review

BACKGROUND

Amidst growing concern about the safety of sport-related repetitive subconcussive head impacts (RSHI), biofluid markers may provide sensitive, informative, and practical assessment of the effects of RSHI exposure.

OBJECTIVE

This scoping review aimed to systematically examine the extent, nature, and quality of available evidence from studies investigating the effects of RSHI on biofluid markers, to identify gaps and to formulate guidelines to inform future research.

METHODS

PRISMA extension for Scoping Reviews guidelines were adhered to. The protocol was pre-registered through publication. MEDLINE, Scopus, SPORTDiscus, CINAHL, PsycINFO, Cochrane Library, OpenGrey, and two clinical trial registries were searched (until March 30, 2022) using descriptors for subconcussive head impacts, biomarkers, and contact sports. Included studies were assessed for risk of bias and quality.

RESULTS

Seventy-nine research publications were included in the review. Forty-nine studies assessed the acute effects, 23 semi-acute and 26 long-term effects of RSHI exposure. The most studied sports were American football, boxing, and soccer, and the most investigated markers were (in descending order): S100 calcium-binding protein beta (S100B), tau, neurofilament light (NfL), glial fibrillary acidic protein (GFAP), neuron-specific enolase (NSE), brain-derived neurotrophic factor (BDNF), phosphorylated tau (p-tau), ubiquitin C-terminal hydrolase L1 (UCH-L1), and hormones. High or moderate bias was found in most studies, and marker-specific conclusions were subject to heterogeneous and limited evidence. Although the evidence is weak, some biofluid markers-such as NfL-appeared to show promise. More markedly, S100B was found to be problematic when evaluating the effects of RSHI in sport.

CONCLUSION

Considering the limitations of the evidence base revealed by this first review dedicated to systematically scoping the evidence of biofluid marker levels following RSHI exposure, the field is evidently still in its infancy. As a result, any recommendation and application is premature. Although some markers show promise for the assessment of brain health following RSHI exposure, future large standardized and better-controlled studies are needed to determine biofluid markers' utility.

Soccer's AI transformation: deep learning's analysis of soccer's pandemic research evolution

Introduction

This paper aims to identify and compare changes in trends and research interests in soccer articles from before and during the COVID-19 pandemic.

Methods

We compared research interests and trends in soccer-related journal articles published before COVID-19 (2018-2020) and during the COVID-19 pandemic (2021-2022) using Bidirectional Encoder Representations from Transformers (BERT) topic modeling.

Results

In both periods, we categorized the social sciences into psychology, sociology, business, and technology, with some interdisciplinary research topics identified, and we identified changes during the COVID-19 pandemic period, including a new approach to home advantage. Furthermore, Sports science and sports medicine had a vast array of subject areas and topics, but some similar themes emerged in both periods and found changes before and during COVID-19. These changes can be broadly categorized into (a) Social Sciences and Technology; (b) Performance training approaches; (c) injury part of body. With training topics being more prominent than match performance during the pandemic; and changes within injuries, with the lower limbs becoming more prominent than the head during the pandemic.

Conclusion

Now that the pandemic has ended, soccer environments and routines have returned to pre-pandemic levels, but the environment that have changed during the pandemic provide an opportunity for researchers and practitioners in the field of soccer to detect post-pandemic changes and identify trends and future directions for research.

Cerebral and cognitive modifications in retired professional soccer players: TC-FOOT protocol, a transverse analytical study

INTRODUCTION

Soccer is the most popular sport in the world. This contact sport carries the risk of exposure to repeated head impacts in the form of subconcussions, defined as minimal brain injuries following head impact, with no symptom of concussion. While it has been suggested that exposure to repetitive subconcussive events can result in long-term neurophysiological modifications, and the later development of chronic traumatic encephalopathy, the consequences of these repeated impacts remain controversial and largely unexplored in the context of soccer players.

METHODS AND ANALYSIS

This is a prospective, single-centre, exposure/non-exposure, transverse study assessing the MRI and neuropsychological abnormalities in professional retired soccer players exposed to subconcussive impacts, compared with high-level athletes not exposed to head impacts. The primary outcome corresponds to the results of MRI by advanced MRI techniques (diffusion tensor, cerebral perfusion, functional MRI, cerebral volumetry and cortical thickness, spectroscopy, susceptibility imaging). Secondary outcomes are the results of the neuropsychological tests: number of errors and time to complete tests. We hypothesise that repeated subconcussive impacts could lead to morphological lesions and impact on soccer players' cognitive skills in the long term.

ETHICS AND DISSEMINATION

Ethics approval has been obtained and the study was approved by the Comité de Protection des Personnes (CPP) No 2021-A01169-32. Study findings will be disseminated by publication in a high-impact international journal. Results will be presented at national and international imaging meetings.

TRIAL REGISTRATION NUMBER

NCT04903015.

Effects of docosahexaenoic acid and eicosapentaoic acid supplementation on white matter integrity after repetitive sub-concussive head impacts during American football: Exploratory neuroimaging findings from a pilot RCT

Context

Repetitive sub-concussive head impacts (RSHIs) are common in American football and result in changes to the microstructural integrity of white matter. Both docosahexaenoic acid (DHA) and eicosapentaoic acid (EPA) supplementation exerted neuroprotective effects against RSHIs in animal models and in a prior study in football players supplemented with DHA alone.

Objective

Here, we present exploratory neuroimaging outcomes from a randomized controlled trial of DHA + EPA supplementation in American football players. We hypothesized that supplementation would result in less white matter integrity loss on diffusion weighted imaging over the season.

Design setting participants

We conducted a double-blind placebo-controlled trial in 38 American football players between June 2019 and January 2020.

Intervention

Participants were randomized to the treatment (2.442 g/day DHA and 1.020 g/day EPA) or placebo group for five times-per-week supplementation for 7 months. Of these, 27 participants were included in the neuroimaging data analysis (n = 16 placebo; n = 11 DHA + EPA).

Exploratory outcome measures

Changes in white matter integrity were quantified using both voxelwise diffusion kurtosis scalars and deterministic tractography at baseline and end of season. Additional neuroimaging outcomes included changes in regional gray matter volume as well as intra-regional, edge-wise, and network level functional connectivity. Serum neurofilament light (NfL) provided a peripheral biomarker of axonal damage.

Results

No voxel-wise between-group differences were identified on diffusion tensor metrics. Deterministic tractography using quantitative anisotropy (QA) revealed increased structural connectivity in ascending corticostriatal fibers and decreased connectivity in long association and commissural fibers in the DHA+EPA group compared to the placebo group. Serum NfL increases were correlated with increased mean (ρ = 0.47), axial (ρ = 0.44), and radial (ρ = 0.51) diffusivity and decreased QA (ρ = -0.52) in the corpus callosum and bilateral corona radiata irrespective of treatment group. DHA + EPA supplementation did preserve default mode/frontoparietal control network connectivity (g = 0.96, p = 0.024).

Conclusions

These exploratory findings did not provide strong evidence that DHA + EPA prevented or protected against axonal damage as quantified via neuroimaging. Neuroprotective effects on functional connectivity were observed despite white matter damage. Further studies with larger samples are needed to fully establish the relationship between omega-3 supplementation, RSHIs, and neuroimaging biomarkers.

Trial registration

ClinicalTrials.gov-NCT04796207.

Serum neurofilament light reflects cognitive dysfunctions in children with obstructive sleep apnea

Background

In children, obstructive sleep apnea (OSA) can cause cognitive dysfunctions. Amyloid-beta and tau are elevated in OSA. Neurofilament light (NfL) is a marker of neuro-axonal damage, but there are no reports of NfL for OSA. The objective was to investigate the serum levels of NfL and tau in children with or without OSA and explore their relationship with cognitive dysfunctions caused by OSA.

Methods

This retrospective case–control study included children diagnosed with adenoid tonsil hypertrophy from July 2017 to September 2019 at the Second Affiliated Hospital of Xi’an Jiaotong University. Correlations between cognitive scores and tau and NfL were examined.

Results

Fifty-six OSA and 49 non-OSA children were included. The serum NfL levels were higher in the OSA group (31.68 (27.29–36.07) pg/ml) than in the non-OSA group (19.13 (17.32–20.95) pg/ml) (P < 0.001). Moreover, NfL was correlated with the course of the disease, apnea–hypopnea index (AHI), obstructive apnea index (OAI), obstructive apnea–hypopnea index (OAHI), average oxygen saturation (SaO₂), respiratory arousal index (RAI), and cognitive dysfunctions evaluated by the Chinese Wechsler Intelligence Scale for Children (C-WISC) (all P < 0.05). The area under the receiver operating characteristics curve (AUC) of NfL was 0.816 (95%CI: 0.736–0.897). Multiple regression analysis revealed that NfL was significantly associated with verbal intelligence quotient (VIQ), performance intelligence quotient (PIQ) and full-scale intelligence quotient (FIQ) (P < 0.001, respectively).

Conclusions

Serum NfL levels are associated with the severity of cognitive dysfunctions in children diagnosed with adenoid tonsil hypertrophy and might be a candidate noninvasive, objective marker to identify cognitive dysfunctions in children with OSA.

Serum neurofilament light concentration does not increase following exposure to low velocity football heading

Objectives: To investigate if heading frequency and impact biomechanics in a single session influence the concentration of serum neurofilament light (NF-L), a sensitive biomarker for axonal damage, up to 7 days after heading incident at ball velocities reflecting basic training drills.Methods: Forty-four males were randomized into either control (n = 8), 10 header (n = 12), 20 header (n = 12) or 40 header (n = 12) groups. Linear and angular head accelerations were quantified during heading. Venous blood samples were taken at baseline, 6 h, 24 h and 7 days after heading. Serum NF-L was quantified using Quanterix NF-L assay kit on the Simoa HD-1 Platform.Results: Serum NF-L did not alter over time (p = 0.44) and was not influenced by number of headers [p = 0.47; mean (95% CI) concentrations at baseline 6.00 pg · ml^-1 (5.00-7.00 pg · ml^-1); 6 h post 6.50 pg · ml^-1 (5.70-7.29 pg · ml^-1); 24 h post 6.07 pg · ml^-1 (5.14-7.01 pg · ml^-1); and 7 days post 6.46 pg · ml^-1 (5.45-7.46 pg · ml^-1)]. There was no relationship between percentage change in NF-L and summed session linear and angular head accelerations.Conclusion: In adult men, heading frequency or impact biomechanics did not affect NF-L response during a single session of headers at ball velocities reflective of basic training tasks.

Effects of sport-related repetitive subconcussive head impacts on biofluid markers: a scoping review protocol

INTRODUCTION

Sport-related repetitive subconcussive head impacts (RSHIs) are increasingly thought to be associated with adverse long-term outcomes. However, owing to potentially subtle effects, accurate assessment of harm to the brain as a consequence of RSHI is a major challenge and an unmet need. Several studies suggest that biofluid markers can be valuable objective tools to aid the diagnosis and injury characterisation and help in medical decision-making. Still, by and large, the results have been limited, heterogeneous and inconsistent. The main aims of this scoping review are therefore (1) to systematically examine the extent, nature and quality of available evidence from studies investigating effects of RSHI on fluid biomarkers and (2) to formulate guidelines and identify gaps with the aim to inform future clinical studies and the development of research priorities.

METHODS AND ANALYSES

We will use a comprehensive search strategy to retrieve all available and relevant articles in the literature. The following electronic databases will be systematically searched: MEDLINE (EBSCO host; from 1809 to 2020); Scopus (from 1788 to 2020); SPORTDiscus (from 1892 to 2020); CINAHL Complete (from 1937 to 2020); PsycINFO (from 1887 to 2020); Cochrane Library (to 2020); OpenGrey (to 2020); ClinicalTrials.gov (to 2020) and WHO International Clinical Trials Registry Platform (to 2020). We will consider primarily biomedical studies evaluating the biofluid markers following RSHI. Two independent reviewers will screen articles for inclusion using predefined eligibility criteria and extract data of retained articles. Disagreements will be resolved through consensus or arbitrated by a third reviewer if necessary. Data will be reported qualitatively given the heterogeneity of the included studies. In synthesising the evidence, we will structure results by markers, sample types, outcomes, sport and timepoints.

ETHICS AND DISSEMINATION

Ethics approval is not required. We will submit results for peer-review publication, and present at relevant conferences.

Neurofilament light chain in patients with a concussion or head impacts: a systematic review and meta-analysis

PURPOSE

Traumatic brain injury is one of the leading causes of disability worldwide. Mild traumatic brain injury (TBI) is the most common and benign form of TBI, usually referred to by the medical term "concussion". The purpose of our systematic review and meta-analysis was to explore the role of serum and CSF neurofilament light chain (NfL) as a potential biomarker in concussion.

METHODS

We systematically searched PubMed, Web of Science, and Cochrane databases using specific keywords. As the primary outcome, we assessed CSF or serum NfL levels in patients with concussion and head impacts versus controls. The role of NfL in patients with concussion and head impacts compared to healthy controls was also assessed, as well as in sports-related and military-related conditions.

RESULTS

From the initial 617 identified studies, we included 24 studies in our qualitative analysis and 14 studies in our meta-analysis. We found a statistically significant increase of serum NfL in patients suffering from a concussion or head impacts compared to controls (p = 0.0023), highlighting its potential role as a biomarker. From our sub-group analyses, sports-related concussion and mild TBI were mostly correlated with increased serum NfL values. Compared to controls, sports-related concussion was significantly associated with higher NfL levels (p = 0.0015), while no association was noted in patients suffering from head impacts or military-related TBI.

CONCLUSION

Serum NfL levels are higher in all patients suffering from concussion compared to healthy controls. The sports-related concussion was specifically associated with higher levels of NfL. Further studies exploring the use of NfL as a diagnostic and prognostic biomarker in mild TBI and head impacts are needed.

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.

Biomarkers for traumatic brain injury: a short review

Cellular response to TBI is a mixture of excitotoxicity, neuroinflammation, and cell death. Biomarkers that can track these lesions and inflammatory processes are being explored for their potential to provide objective measures in the evaluation of TBI, from prehospital care to rehabilitation. By understanding the pathways involved, we could be able to improve diagnostic accuracy, guide management, and prevent long-term disability. We listed some of the recent advances in this translational, intriguing, fast-growing field. Although the knowledge gaps are still significant, some markers are showing promising results and could be helping patients in the near future.

Serum Protein Biomarker Findings Reflective of Oxidative Stress and Vascular Abnormalities in Male, but Not Female, Collision Sport Athletes

Studies have indicated that concussive and sub-concussive brain injuries that are frequent during collision sports may lead to long-term neurological abnormalities, however there is a knowledge gap on how biological sex modifies outcomes. Blood-based biomarkers can help to identify the molecular pathology induced by brain injuries and to better understand how biological sex affects the molecular changes. We therefore analyzed serum protein biomarkers in male (n = 50) and female (n = 33) amateur Australian rules footballers (i.e., Australia's most participated collision sport), both with a history of concussion (HoC) and without a history of concussion (NoHoC). These profiles were compared to those of age-matched control male (n = 24) and female (n = 20) athletes with no history of neurotrauma or participation in collision sports. Serum levels of protein markers indicative of neuronal, axonal and glial injury (UCH-L1, NfL, tau, p-tau, GFAP, BLBP, PEA15), metabolic (4-HNE) and vascular changes (VEGF-A, vWF, CLDN5), and inflammation (HMGB1) were assessed using reverse phase protein microarrays. Male, but not female, footballers had increased serum levels of VEGF-A compared to controls regardless of concussion history. In addition, only male footballers who had HoC had increased serum levels of 4-HNE. These findings being restricted to males may be related to shorter collision sport career lengths for females compared to males. In summary, these findings show that male Australian rules footballers have elevated levels of serum biomarkers indicative of vascular abnormalities (VEGF-A) and oxidative stress (4-HNE) in comparison to non-collision control athletes. While future studies are required to determine how these findings relate to neurological function, serum levels of VEGF-A and 4-HNE may be useful to monitor subclinical neurological injury in males participating in collision sports.