Psychological and Physiological Markers of Stress in Concussed Athletes Across Recovery Milestones

Adolescents With a High Burden of New-Onset Mood Symptoms After Sport-Related Concussion Benefit From Prescribed Aerobic Exercise, a Secondary Analysis of 2 Randomized Controlled Trials

OBJECTIVE

Approximately 20% of students with sport-related concussion (SRC) report new symptoms of anxiety and depression which may be associated with delayed recovery and increased risk for developing a mood disorder. Early prescribed aerobic exercise facilitates recovery in athletes with concussion-related exercise intolerance. We studied the effect of aerobic exercise treatment on new mood symptoms early after SRC.

DESIGN

Exploratory secondary analysis of 2 randomized controlled trials (RCT).

SETTING

Sports medicine clinics associated with UB (Buffalo, NY), CHOP (Philadelphia, PA), and Boston Children's Hospital (Boston, MA).

PARTICIPANTS

Male and female adolescents (aged 13-18 years) diagnosed with SRC (2-10 days since injury).

INTERVENTIONS

Participants were randomized to individualized targeted heart rate aerobic exercise (n = 102) or to a placebo intervention designed to mimic relative rest (n = 96).

MAIN OUTCOME MEASURES

Incidence of Persisting Post-Concussive Symptoms (PPCS, symptoms ≥28 days).

RESULTS

First RCT recruited from 2016 to 2018 and the second from 2018 to 2020. Of 198 adolescents, 156 (79%) reported a low burden (mean 1.2 ± 1.65/24) while 42 (21%) reported a high burden (mean 9.74 ± 3.70/24) of emotional symptoms before randomization. Intervention hazard ratio for developing PPCS for low burden was 0.767 (95% CI, 0.546-1.079; P = 0.128; β = 0.085) and for high burden was 0.290 (95% CI, 0.123-0.683; P = 0.005; β = 0.732).

CONCLUSIONS

High burden of mood symptoms early after injury increases risk for PPCS, but the sports medicine model of providing early targeted aerobic exercise treatment reduces it. Nonsports medicine clinicians who treat patients with a high burden of new mood symptoms after concussion should consider prescribing aerobic exercise treatment to reduce the risk of PPCS and a mood disorder.

Heart rate variability (HRV) after traumatic brain injury (TBI): a scoping review

BACKGROUND

Heart rate variability (HRV), defined as the variability between successive heart beats, is a noninvasive measure of autonomic nervous system (ANS) function, which may be altered following traumatic brain injury (TBI). This scoping review summarizes the existing literature regarding changes in HRV after TBI as well as the association between measures of HRV and outcomes following TBI.

METHODS

A literature search for articles assessing 'heart rate variability' and 'brain injury' or 'concussion' was completed. Articles were included if HRV was measured in human subjects with TBI or concussion. Review articles, protocol papers, and studies including non-traumatic injuries were excluded.

RESULTS

Sixty-three articles were included in this review. Varied methods were used to measure HRV in the different studies. Forty articles included information about differences in HRV measures after TBI and/or longitudinal changes after TBI. Fifteen studies assessed HRV and symptoms following TBI, and 15 studies assessed HRV and either functional or cognitive outcomes after TBI.

CONCLUSIONS

HRV has been studied in the context of mortality, clinical symptoms, and medical, functional, or cognitive outcomes following TBI. Methods used to measure HRV have varied amongst the different studies, which may impact findings, standardized protocols are needed for future research.

Autonomic nervous system and endocrine system response to upper or lower cervical spine mobilization in males with persistent post-concussion symptoms: a proof-of-concept trial

INTRODUCTION

The peripheral stress response, consisting of the autonomic nervous system (ANS) and hypothalamic pituitary adrenal-axis (HPA-axis), functions to maintain homeostasis in response to stressors. Cervical spine manual therapy has been shown to differentially modulate the stress response in healthy populations. No study has investigated whether cervical spine mobilizations can differentially modulate the stress response in individuals with persistent post-concussion symptoms (PPCS), a population characterized by a dysfunctional stress response.

METHODS

A randomized, controlled, parallel design trial was performed to investigate whether upper or lower cervical spine mobilization can differentially modulate components of the stress response in individuals with PPCS. The outcomes were salivary cortisol (sCOR) concentration (primary) and the HRV metric, rMSSD, measured with a smartphone application (secondary). Nineteen males diagnosed with PPCS, aged 19-35, were included. Participants were randomly assigned into either intervention group, upper (n = 10) or lower (n = 9) cervical spine mobilization. Each outcome was collected at different time points, pre- and post-intervention. Statistical analyses were performed using the Friedman's Two-Way ANOVA, Mann-Whitney U test, and Wilcoxon Signed Rank Test.

RESULTS

There was a statistically significant within-group reduction in sCOR concentration 30 minutes following lower cervical spine mobilizations and statistically significant within-group increase in rMSSD 30 minutes following upper cervical spine mobilizations.

CONCLUSION

The results of this trial provide preliminary evidence for cervical spine mobilizations to differentially modulate components of the stress response at specific time points. Understanding the mechanisms of the effect of cervical spine mobilizations on the stress response provides a novel rationale for selecting cervical spine mobilizations to rehabilitate individuals with PPCS.

Evaluation of Quantitative Pupillometry in Acute Postinjury Pediatric Concussion

BACKGROUND

Although millions of children sustain concussions each year, a rapid and objective test for concussion has remained elusive. The aim of this study was to investigate quantitative pupillometry in pediatric patients in the acute, postinjury setting.

METHODS

This was a prospective case-control study of concussed patients presenting to the emergency department within 72 hours of injury. Pupillary measurements were gathered using NeurOptics' PLR 3000; evaluation included a symptom checklist and neurocognitive assessment. Data were analyzed using descriptive statistics and regression models.

RESULTS

A total of 126 participants were enrolled. One significant difference in pupillometry between concussed and control participants was found: left minimum pupil diameter in 12- to 18 year-olds (P = 0.02). Models demonstrating odds of a concussion revealed significant associations for time to 75% recovery (T75) of the left pupil in five- to 11-year-olds and average dilation velocity of the left pupil in 12- to 18-year-olds (P = 0.03 and 0.02 respectively). Models predicting symptom improvement showed one significant association: percent change of the right pupil in five-to-11-year-olds (P = 0.02). Models predicting neurocognitive improvement in 12- to 18-year-olds demonstrated significant association in T75 in the left pupil for visual memory, visual motor processing speed, and reaction time (P = 0.002, P = 0.04, P = 0.04).

CONCLUSIONS

The limited statistically significant associations found in this study suggest that pupillometry may not be useful in pediatrics in the acute postinjury setting for either the diagnosis of concussion or to stratify risk for prolonged recovery.

Assessment of cardiovascular functioning following sport-related concussion: A physiological perspective

There is still much uncertainty surrounding the approach to diagnosing and managing a sport-related concussion (SRC). Neurobiological recovery may extend beyond clinical recovery following SRC, highlighting the need for objective physiological parameters to guide diagnosis and management. With an increased understanding of the connection between the heart and the brain, the utility of assessing cardiovascular functioning following SRC has gained attention. As such, this review focuses on the assessment of cardiovascular parameters in the context of SRC. Although conflicting results have been reported, decreased heart rate variability, blood pressure variability, and systolic (ejection) time, in addition to increased spontaneous baroreflex sensitivity and magnitude of atrial contraction have been shown in acute SRC. We propose that these findings result from the neurometabolic cascade triggered by a concussion and represent alterations in myocardial calcium handling, autonomic dysfunction, and an exaggerated compensatory response that attempts to maintain homeostasis following a SRC. Assessment of the cardiovascular system has the potential to assist in diagnosing and managing SRC, contributing to a more comprehensive and multimodal assessment strategy.

Patterns and predictors of concussion symptom presentations in NCAA athletes

Sport-related concussion (SRC) is a complex injury, and SRCs are notably prevalent among National Collegiate Athletic Association (NCAA) athletes. We analysed SRCs and associated exposure data collected within the NCAA Injury Surveillance Program during 2014-2019. A total of 1,709 SRCs were reported with complete symptom profiles during the study period (Women's sports n = 499; Men's sports n = 1,210). Event type and academic class year most commonly predicted specific symptom presentations among athletes in men's sports, while symptom presentation among athletes in women's sports was most commonly predicted by class year and sport classification. We observed 78 and 69 significant pairwise symptom dependencies in men's and women's sports athletes, respectively; odds of longer symptom resolution time were higher with greater counts of symptoms with strongest cross-domain associations. Our findings highlight several contextual predictors of specific symptom presentations and identify parsimonious symptom subsets that may indicate protracted recovery among men's and women's sports athletes.

History of concussion and lowered heart rate variability at rest beyond symptom recovery: a systematic review and meta-analysis

Introduction

Concussion is a growing concern in worldwide sporting culture. Heart rate variability (HRV) is closely tied with autonomic nervous system (ANS) deficits that arise from a concussion. The objective of this review was to determine if a history of concussion (HOC) can impact HRV values in the time-domain in individuals at rest. This review works to add to the literature surrounding HRV testing and if it can be used to check for brain vulnerabilities beyond the recovery of concussion symptoms.

Materials and methods

The systematic review was conducted using the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) method. A computer based systematic review scanned articles dating from 1996 to June 2023 through PubMed, Cochrane Library, Google Scholar, and EMBASE databases. A risk of bias assessment was conducted using the ROBINS-E tool. The average difference in time between heartbeats (MeanNN), the standard deviation of the differences (SDNN), and the root mean squared of the successive intervals (RMSSD) were measured.

Results

Six total studies were found that fit the inclusion criteria including a total of 242 participants (133 without HOC, 109 with HOC). The average age of the control group was 23.3 ± 8.2, while the average age of the history of TBI group was 25.4 ± 9.7, with no significant difference between the groups (p = 0.202). Four of the studies reported no significant difference in any of the three measures, while two of the studies reported significant difference for all three measures. The meta-analysis was conducted and found that MeanNN (p = 0.03) and RMSSD (p = 0.04) reached statistical significance, while SDNN did not (p = 0.11).

Conclusion

The results of this meta-analysis showed significant difference in two of the three HRV time-domain parameters evaluated. It demonstrates that there can be lowered HRV values that expand beyond the recovery of symptoms, reflecting an extensive period of ANS susceptibility after a concussion. This may be an important variable in determining an athlete's return to play (RTP). Lack of homogenous study populations and testing methods introduces potential for bias and confounding factors, such as gender or age. Future studies should focus on baseline tests to compare individuals to themselves rather than matched controls.

Non-invasive fluid biomarkers in the diagnosis of mild traumatic brain injury (mTBI): a systematic review

BACKGROUND

Despite approximately 55.9 million annual mild traumatic brain injuries (mTBIs) worldwide, the accurate diagnosis of mTBI continues to challenge clinicians due to symptom ambiguity, reliance on subjective report and presentation variability. Non-invasive fluid biomarkers of mTBI offer a biological measure to diagnose and monitor mTBI without the need for blood draws or neuroimaging. The objective of this study is to systematically review the utility of such biomarkers to diagnose mTBI and predict disease progression.

METHODS

A systematic review performed in PubMed, Scopus, Cochrane and Web of Science followed by a manual search of references without a specified timeframe. Search strings were generated and run (27 June 2022) by a research librarian. Studies were included if they: (1) included human mTBI subjects, (2) assessed utility of a non-invasive biomarker and (3) published in English. Exclusion criteria were (1) non-mTBI subjects, (2) mTBI not assessed separately from moderate/severe TBI, (3) required intracranial haemorrhage or (4) solely assesses genetic susceptibility to mTBI.

RESULTS

A total of 29 studies from 27 subject populations (1268 mTBI subjects) passed the inclusion and exclusion criteria. Twelve biomarkers were studied. Salivary RNAs, including microRNA, were assessed in 11 studies. Cortisol and melatonin were assessed in four and three studies, respectively. Eight salivary and two urinary biomarkers contained diagnostic or disease monitoring capability.

DISCUSSION

This systematic review identified several salivary and urinary biomarkers that demonstrate the potential to be used as a diagnostic, prognostic and monitoring tool for mTBI. Further research should examine miRNA-based models for diagnostic and predictive utility in patients with mTBI.

PROSPERO REGISTRATION NUMBER

CRD42022329293.

CARE4Kids Study: Endophenotypes of Persistent Post-Concussive Symptoms in Adolescents: Study Rationale and Protocol

Treatment of youth concussion during the acute phase continues to evolve, and this has led to the emergence of guidelines to direct care. While symptoms after concussion typically resolve in 14-28 days, a portion (∼20%) of adolescents endorse persistent post-concussive symptoms (PPCS) beyond normal resolution. This report outlines a study implemented in response to the National Institute of Neurological Diseases and Stroke call for the development and initial clinical validation of objective biological measures to predict risk of PPCS in adolescents. We describe our plans for recruitment of a Development cohort of 11- to 17-year-old youth with concussion, and collection of autonomic, neurocognitive, biofluid, and imaging biomarkers. The most promising of these measures will then be validated in a separate Validation cohort of youth with concussion, and a final, clinically useful algorithm will be developed and disseminated. Upon completion of this study, we will have generated a battery of measures predictive of high risk for PPCS, which will allow for identification and testing of interventions to prevent PPCS in the most high-risk youth.

Heart Rate Variability in Concussed College Athletes: Follow-Up Study and Biological Sex Differences

Finding reliable biomarkers to assess concussions could play a pivotal role in diagnosis, monitoring, and predicting associated risks. The present study aimed to explore the use of heart rate variability (HRV) in the follow-up of concussions among college athletes and to investigate the relationships between biological sex, symptomatology, and HRV values at baseline and after a concussion. Correlations between measures were also analyzed. A total of 169 (55 females) athletes aged 16 to 22 years old completed baseline testing, and 30 (8 females) concussion cases were followed. Baseline assessment (T1) included psychosocial and psychological questionnaires, symptoms report, and four minutes of HRV recording. In the event of a concussion, athletes underwent re-testing within 72 h (T2) and before returning to play (T3). Baseline findings revealed that girls had higher %VLF while sitting than boys, and a small negligible correlation was identified between %HF and total symptoms score as well as %HF and affective sx. Post-concussion analyses demonstrated a significant effect of time × position × biological sex for %HF, where girls exhibited higher %HF at T3. These findings suggest disruptions in HRV following a concussion and underscore biological sex as an important factor in the analysis of HRV variation in concussion recovery trajectory.

Heart rate variability behavior in athletes after a sports concussion: A systematic review

OBJECTIVE

This systematic review aims to investigate the adaptations of the autonomic nervous system (ANS) after a concussion by measuring HRV in athletes over the age of 16 after injury.

METHODS

This systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA). Web of Science, Pubmed, SCOPUS, and Sport Discus were searched using predefined search terms to identify relevant original cross-sectional, longitudinal, and cohort epidemiological studies published before December 2021.

RESULTS

After screening 1737 potential articles, four studies met the inclusion criteria. Studies included participants with concussion (n = 63) and healthy control athletes (n = 140) who practised different sports. Two studies describe a decrease in HRV following a sports concussion, and one proposed that the resolution of symptoms does not necessarily reflect ANS recovery. Lastly, one study concluded that submaximal exercise induces alteration in ANS, not seen in rest after an injury.

CONCLUSIONS

In the frequency domain, a decrease in high frequency power and an increase of low frequency/high frequency ratio is expected, as the activity of the sympathetic nervous system increases, and the parasympathetic nervous system decreases after injury. In the frequency domain, heart rate variability (HRV) may help monitor the activity of ANS evaluating signals of somatic tissue distress and early identification of other types of musculoskeletal injuries. Further research should investigate the relationship between HRV and other musculoskeletal injuries.

Clinical recovery from concussion-return to school and sport: a systematic review and meta-analysis

OBJECTIVE

To define the time frames, measures used and modifying factors influencing recovery, return to school/learn (RTL) and return to sport (RTS) after sport-related concussion (SRC).

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

8 databases searched through 22 March 2022.

ELIGIBILITY CRITERIA

Studies with diagnosed/suspected SRC and interventions facilitating RTL/RTS or investigating the time and modifying factors for clinical recovery. Outcomes included days until symptom free, days until RTL and days until RTS. We documented study design, population, methodology and results. Risk of bias was evaluated using a modified Scottish Intercollegiate Guidelines Network tool.

RESULTS

278 studies were included (80.6% cohort studies and 92.8% from North America). 7.9% were considered high-quality studies, while 23.0% were considered high risk of bias and inadmissible. The mean days until symptom free was 14.0 days (95% CI: 12.7, 15.4; I²=98.0%). The mean days until RTL was 8.3 (95% CI: 5.6, 11.1; I²=99.3%), with 93% of athletes having a full RTL by 10 days without new academic support. The mean days until RTS was 19.8 days (95% CI: 18.8, 20.7; I²=99.3%), with high heterogeneity between studies. Several measures define and track recovery, with initial symptom burden remaining the strongest predictor of longer days until RTS. Continuing to play and delayed access to healthcare providers were associated with longer recovery. Premorbid and postmorbid factors (eg, depression/anxiety, migraine history) may modify recovery time frames. Though point estimates suggest that female sex or younger age cohorts take longer to recover, the heterogeneity of study designs, outcomes and overlap in CIs with male sex or older age cohorts suggests that all have similar recovery patterns.

CONCLUSION

Most athletes have full RTL by 10 days but take twice as long for an RTS.

PROSPERO REGISTRATION NUMBER

CRD42020159928.

Role of biomarkers and emerging technologies in defining and assessing neurobiological recovery after sport-related concussion: a systematic review

OBJECTIVE

Determine the role of fluid-based biomarkers, advanced neuroimaging, genetic testing and emerging technologies in defining and assessing neurobiological recovery after sport-related concussion (SRC).

DESIGN

Systematic review.

DATA SOURCES

Searches of seven databases from 1 January 2001 through 24 March 2022 using keywords and index terms relevant to concussion, sports and neurobiological recovery. Separate reviews were conducted for studies involving neuroimaging, fluid biomarkers, genetic testing and emerging technologies. A standardised method and data extraction tool was used to document the study design, population, methodology and results. Reviewers also rated the risk of bias and quality of each study.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Studies were included if they: (1) were published in English; (2) represented original research; (3) involved human research; (4) pertained only to SRC; (5) included data involving neuroimaging (including electrophysiological testing), fluid biomarkers or genetic testing or other advanced technologies used to assess neurobiological recovery after SRC; (6) had a minimum of one data collection point within 6 months post-SRC; and (7) contained a minimum sample size of 10 participants.

RESULTS

A total of 205 studies met inclusion criteria, including 81 neuroimaging, 50 fluid biomarkers, 5 genetic testing, 73 advanced technologies studies (4 studies overlapped two separate domains). Numerous studies have demonstrated the ability of neuroimaging and fluid-based biomarkers to detect the acute effects of concussion and to track neurobiological recovery after injury. Recent studies have also reported on the diagnostic and prognostic performance of emerging technologies in the assessment of SRC. In sum, the available evidence reinforces the theory that physiological recovery may persist beyond clinical recovery after SRC. The potential role of genetic testing remains unclear based on limited research.

CONCLUSIONS

Advanced neuroimaging, fluid-based biomarkers, genetic testing and emerging technologies are valuable research tools for the study of SRC, but there is not sufficient evidence to recommend their use in clinical practice.

PROSPERO REGISTRATION NUMBER

CRD42020164558.

Clinical Mental Health Measures and Prediction of Postconcussion Musculoskeletal Injury

CONTEXT

The rate of lower extremity musculoskeletal injury (LE MSK) is elevated after concussion; however, the underlying mechanism has not been elucidated. Physical characteristics have been investigated despite poorer mental health being a common postconcussion complaint and linked to MSKs.

OBJECTIVE

To evaluate the role of mental health as a predictor of postconcussion LE MSK.

DESIGN

Case-control study.

SETTING

Intercollegiate athletic training facility.

PATIENTS OR OTHER PARTICIPANTS

A total of 67 National Collegiate Athletic Association Division I student-athletes (n = 39 females) who had been diagnosed with a sport-related concussion.

MAIN OUTCOME MEASURE(S)

The Brief Symptom Inventory-18, Hospital Anxiety and Depression Scale, and Satisfaction With Life Scale (SWLS) measures were completed at baseline (preseason) and on the day participants were cleared for unrestricted return to play (RTP) after a concussion. Two binary logistic regressions were used to predict postconcussion LE MSK within a year, one for the baseline time point and the second for the RTP time point. A 2 (group: LE MSK, no LE MSK)-by-2 (time: baseline, RTP) repeated-measures analysis of variance compared performance between baseline and RTP.

RESULTS

Subsequent LE MSKs were sustained by 44 participants (65.7%). The only significant predictor of postconcussion LE MSK was the SWLS score at RTP, with Exp(B) = 0.64, indicating that an increased (improved) SWLS score was associated with a lower LE MSK rate. No significant interactions were present between mental health measures and subsequent MSK (P values = .105-.885).

CONCLUSIONS

Limited associations were evident between postconcussion LE MSK and scores on commonly used measures of anxiety, depression, and satisfaction with life. Reported increased satisfaction with life was associated with a decreased injury risk, which warrants further attention. Our results suggest that these measures of anxiety, depression, and satisfaction with life have limited value in assisting sports medicine clinicians with determining which student-athletes are at elevated risk of postconcussion LE MSK.

Cerebrovascular Reactivity and Concussion

Cerebrovascular reactivity (CVR) reflects the change in cerebral blood flow in response to vasodilatory stimuli enabling assessment of the health of the cerebral vasculature. Recent advances in the quantitative delivery of CO2 stimuli with computer-controlled sequential gas delivery have enabled mapping of the speed and magnitude of response to flow stimuli. These CVR advances when applied to patients with acute concussion have unexpectedly shown faster speed and greater magnitude of responses unseen in other diseases that typically show the opposite effects. The strength of the CVR alterations have diagnostic potential in single subjects with AUC values in the 0.90-0.94 range.

Home-Based Measurements of Nocturnal Cardiac Parasympathetic Activity in Athletes during Return to Sport after Sport-Related Concussion

Sport-related concussions (SRC) are characterized by impaired autonomic control. Heart rate variability (HRV) offers easily obtainable diagnostic approaches to SRC-associated dysautonomia, but studies investigating HRV during sleep, a crucial time for post-traumatic cerebral regeneration, are relatively sparse. The aim of this study was to assess nocturnal HRV in athletes during their return to sports (RTS) after SRC in their home environment using wireless wrist sensors (E4, Empatica, Milan, Italy) and to explore possible relations with clinical concussion-associated sleep symptoms. Eighteen SRC athletes wore a wrist sensor obtaining photoplethysmographic data at night during RTS as well as one night after full clinical recovery post RTS (>3 weeks). Nocturnal heart rate and parasympathetic activity of HRV (RMSSD) were calculated and compared using the Mann-Whitney U Test to values of eighteen; matched by sex, age, sport, and expertise, control athletes underwent the identical protocol. During RTS, nocturnal RMSSD of SRC athletes (Mdn = 77.74 ms) showed a trend compared to controls (Mdn = 95.68 ms, p = 0.021, r = -0.382, p adjusted using false discovery rate = 0.126) and positively correlated to "drowsiness" (r = 0.523, p = 0.023, p adjusted = 0.046). Post RTS, no differences in RMSSD between groups were detected. The presented findings in nocturnal cardiac parasympathetic activity during nights of RTS in SRC athletes might be a result of concussion, although its relation to recovery still needs to be elucidated. Utilization of wireless sensors and wearable technologies in home-based settings offer a possibility to obtain helpful objective data in the management of SRC.

Median Time to Return to Sports After Concussion Is Within 21 Days in 80% of Published Studies

PURPOSE

To perform a systematic review of the literature and evaluate the return to play (RTP) time frame after a concussion diagnosis. Our secondary purpose was to analyze and compare different prognostic variables affecting concussions, time to return to school, time to symptom resolution of concussive symptoms, and time each patient spent in the RTP protocol.

METHODS

A PubMed, Scopus, Medline, Embase, and Cochrane Library database literature review was performed in August 2022. The studies needed to report, in days, the length of time a patient/athlete was removed from play due to concussion management. The Risk of Bias in Non-Randomized Studies of Interventions tool was used for risk of bias for each study, and Methodological Index for Non-Randomized Studies criteria were used for quality assessment.

RESULTS

There were 65 studies included in the systematic review and a total of 21,966 patients evaluated. The RTP time intervals ranged from 1 to 1,820 days, with 80.7% of the median RTP time frames for each study within 21 days. Preconcussion risk factors for prolonged RTP included female sex, younger age, presence of psychiatric disorders, and history of previous concussion. Postconcussion risk factors included severe symptom scores at initial clinic visit, loss of consciousness, nonelite athletes, and delayed removal from competition. The most common sports resulting in concussion were contact sports, most commonly football and soccer. Median time to return to school was 3 to 23 days. Median time to symptom resolution ranged from 2 to 11 days. Median time in RTP protocol was 1 to 6 days.

CONCLUSIONS

Median time to return to sports after concussion is within 21 days in 80% of published studies.

LEVEL OF EVIDENCE

IV, systematic review of Level I to IV studies.

Saliva Cortisol as a Biomarker of Injury in Youth Sport-Related Concussion

Increasing rates of sport-related concussion (SRC) in youth impose a significant burden on public health systems and the lives of young athletes. Accurate prediction for those likely to develop persistent post-concussion symptomology (PPCS) using a fluid biomarker, reflecting both acute injury and recovery processes, would provide the opportunity for early intervention. Cortisol, a stress hormone released through the hypothalamic-pituitary-adrenal (HPA) axis following injury, may provide a missing physiological link to clinical recovery. This cohort study investigated the change in saliva cortisol following SRC and the association between cortisol and symptom burden in pediatric ice hockey players. Further, the association between cortisol levels and medical clearance to return to play was explored. In total, cortisol samples from 233 players were included; 165 athletes (23.6% female) provided pre-injury saliva and 68 athletes (19.1% female) provided post-SRC saliva samples for cortisol analysis. Quantile (median) regressions were used to compare cortisol between pre-injury and post-SRC groups, and the association between total symptoms (/22) and symptom severity scores (/132) reported on the Sport Concussion Assessment Tool (SCAT)3/SCAT5 and post-SRC cortisol (adjusting for age, sex, history of concussion, and time from injury to sample collection). Results demonstrated significantly lower saliva cortisol in post-SRC athletes compared with the pre-injury group (β = -0.62, 95% confidence interval [CI; -1.08, -0.16], p = 0.009). Post-SRC cortisol was not significantly associated with the SCAT3/SCAT5 symptom totals or symptom severity scores; however, females were found to report more symptoms (β = 6.95, 95% CI [0.35, 13.55], p = 0.040) and greater symptom severity (β = 23.87, 95% CI [9.58, 38.15], p = 0.002) compared with males. Exploratory time-to-event analysis revealed a point estimate suggesting a potential association between low cortisol levels and days to medical clearance to return to play. Although preliminary, these findings suggest that the HPA axis may be dysregulated post-SRC. Further, our exploratory analysis and case presentation of post-injury outliers highlight the need to further research cortisol as a prognostic biomarker to inform individualized sex-specific care after SRC.

Concussion and Psychological Effects: A Review of Recent Literature

ABSTRACT

The aim of this article is to provide an up-to-date review of psychological changes in association with postconcussive athletes. In particular, this article focused on the symptomatology, risk factors, and treatment of psychiatric diagnoses in patients who suffered a sports-related concussion (SRC). After an extensive review of prior and current literature, there is significant evidence that demonstrates an association of changes in mood and behavior, including new or worsening symptoms of anxiety, depression, and difficulty with attention and concentration in those who are recovering from a concussion. The goal of care in these patients is to identify and treat these psychological symptoms early to have more favorable long-term outcomes. Primary treatment should focus on psychotherapy; however, other considerations may be warranted in certain cases, such as selective serotonin reuptake inhibitors for depression and tricyclic antidepressants and gabapentin for short-term cognitive symptom improvement.

Ten-Word List Performance in Healthy Athletes and Athletes at 3-to-5 Days Following Concussion

OBJECTIVE

Although the word recall component of the Sport Concussion Assessment Tool (SCAT) was updated from 5-to-10 words, its clinical utility across athletic populations remains unknown. The purpose of this study was to provide normative data on the SCAT-5 10-word test and examine its discriminative ability between healthy university level athletes and those with sport-related concussion (SRC).

DESIGN

Cross-sectional.

SETTING

University.

PARTICIPANTS

Three hundred sixty-three (363, M = 220, F = 153) healthy athletes and 49 (M = 30, F = 19) athletes following SRC.

INDEPENDENT VARIABLE

Healthy athletes measured preseason were compared with athletes following an SRC (median = 4.0 days postinjury).

MAIN OUTCOME MEASURE

Ten-word list performance from the SCAT-5.

RESULTS

There were no significant differences in either immediate ( P = 0.228, Cohen's D = 0.18) or delayed ( P = 0.908, Cohen's D = 0.02) recall tests between athletes with SRC and healthy athletes; the null findings extended to both the male and female subset comparisons. Among healthy athletes, females outperformed males on both immediate (mean difference = 1.0, P < 0.001) and delayed (mean difference = 0.5, P = 0.006) recall tasks.

CONCLUSION

Concussion does not seem to impact immediate or delayed recall of the 10-word list in the subacute period following injury. Practitioners should be mindful of sex differences and the time point of administration following injury.

Which psychosocial factors are associated with return to sport following concussion? A systematic review

BACKGROUND

Psychosocial factors predict recurrent injury and return to preinjury level of performance following orthopedic injury but are poorly understood following concussion. Current management protocols prioritize physical measures of recovery. Therefore, the objective of this study was to describe the psychosocial factors associated with return to sport (RTS) and how they are measured in athletes who sustained a concussion.

METHODS

MEDLINE, Embase, APA PsycINFO, CINAHL, and SPORTDiscus were searched through February 2, 2021. Eligible studies included original peer-reviewed publications describing psychosocial factors associated with RTS following a diagnosed concussion. The primary outcome was scales or measures employed and/or key thematic concepts.

RESULTS

Of the 3615 studies identified, 10 quantitative cohort studies (Oxford Centre for Evidence-Based Medicine Level-3) representing 2032 athletes (85% male; high-school and collegiate collision/contact athletes) and 4 qualitative studies representing 66 athletes (74% male; 70% American football; aged 9-28 years) were included. We identified 3 overarching themes and 10 outcome measures related to psychosocial factors associated with RTS following concussion: (a) fear (e.g, of recurrent concussion, of RTS, of losing playing status); (b) emotional factors (e.g, depression, anxiety, perceived stress, mental health, disturbance mood); and (c) contextual factors (e.g, social support, pressure, sense of identity).

CONCLUSION

Although current medical clearance decisions prioritize physical measures of recovery, evidence suggests diverse psychosocial factors influence RTS following concussion. It remains unclear which psychosocial factors contribute to a successful RTS, including the influence of sex/gender and age. Future studies should evaluate the association of psychological readiness with physical measures of recovery at medical clearance, preinjury level of performance, and risk of recurrent concussion to support RTS clinical decision-making.

Post-Concussive Orthostatic Tachycardia is Distinct from Postural Orthostatic Tachycardia Syndrome (POTS) in Children and Adolescents

Background: Orthostatic tachycardia (OT) affects some patients after concussion/mild traumatic brain injury (mTBI). In this study, we sought to identify the factors associated with increased risk for OT in patients with mTBI. Methods: We conducted a retrospective review of 268 patients (8-25 years) with mTBI/concussion to determine the prevalence of OT, defined as orthostatic heart rate change ≥40 bpm for those ≤19 years of age and ≥30 bpm on active standing test for those >19 years of age. Results: Among the study population, 7% (n = 19) exhibited post-concussive OT. The only significant difference between OT and non-OT groups was that history of prior concussion was more prevalent in the OT group. Conclusion: A substantial subset (7%) of concussion clinic patients exhibit OT. While POTS literature describes female and adolescent predominance, post-concussive OT had similar prevalence across age and gender groups in this study, suggesting that it may be distinct from POTS.

ASSOCIATION BETWEEN ALTERED CORTISOL PROFILES AND NEUROBEHAVIORAL IMPAIRMENT FOLLOWING mTBI IN COLLEGE STUDENTS

Mild Traumatic Brain Injury (mTBI) is the most common form of TBI, accounting for over 2.5 million TBI cases in the United States annually. Identification of easily obtainable biomarkers that track strongly with mTBI symptoms may improve our understanding of biological factors that contribute to mTBI symptom profiles and long-term outcomes. Notably, some individuals with mTBI exhibit circadian disruptions and elevated stress sensitivity, which in other clinical groups often correlate with disrupted secretion of cortisol, a glucocorticoid hormone that coordinates circadian and stress physiology. Here, we sought to determine whether cortisol profiles could serve as a biomarker to complement the assessment of neurobehavioral sequelae following mTBI. We partnered with our on-campus health clinic to recruit college students seeking medical care following mTBI (n=46) and compared this population to a well-matched non-injured student control group (n=44). We collected data at an initial visit (shortly after injury in mTBI subjects) and one week later. At each visit, we evaluated neurobehavioral function using the Automated Neuropsychological Assessment Metric (ANAM). Our subjects then provided cortisol samples through at-home saliva collection. We observed strong coherence between ANAM subjective and objective measures, indicating significant multidimensional impairment in those with mTBI. Further, female mTBI subjects exhibited diminished neurobehavioral function compared to males. Regardless of sex, decreased amplitude of diurnal cortisol and a blunted cortisol awakening response predicted mTBI symptom severity and neurobehavioral impairment. Taken together, these findings suggest that salivary cortisol profiles may be a sensitive biomarker for studying underlying biological factors that impact mTBI outcomes.

Autonomic dysfunction in adults following mild traumatic brain injury: A systematic review

BACKGROUND

Increasing evidence suggests autonomic nervous system (ANS) dysfunction may occur following mild traumatic brain injury (mTBI). Measures of heart rate, heart rate variability, blood pressure and baroreceptor sensitivity can be used to evaluate ANS dysfunction following mTBI.

OBJECTIVE

Summarize the evidence for ANS dysfunction in adults following mTBI.

METHODS

A search of Embase, MEDLINE, Cochrane Central Register, PsycINFO, CINAHL and SPORTDiscus databases was conducted. Search topics included: mTBI and ANS. Identified abstracts were independently reviewed by 2 reviewers followed by full text screening. Risk of bias was assessed using a modified SIGN checklist. A structured synthesis was performed.

RESULTS

Thirty-nine studies (combined 1,467 participants diagnosed with mTBI) evaluating ANS function were included. ANS function was evaluated under various conditions including: rest, during exertion, cold pressor test, Valsalva maneuver, using face cooling and eyeball pressure paradigms. Short-term or ultra-short-term recordings were most common. The majority of studies (28/39) were rated as "unacceptable" for quality of evidence.

CONCLUSIONS

Altered parameters of ANS function have been reported in multiple conditions following mTBI, both acutely and in the post-acute/chronic stages of recovery. However, due to methodological limitations, conclusions regarding the severity and timing of ANS dysfunction following mTBI cannot be drawn.

A Randomized Controlled Trial of Precision Vestibular Rehabilitation in Adolescents following Concussion: Preliminary Findings

OBJECTIVE

To compare the effectiveness of a 4-week precision vestibular rehabilitation intervention compared with a behavioral management control intervention for adolescents with vestibular symptoms/impairment within 21 days of a concussion.

STUDY DESIGN

This study used double-blind, randomized controlled trial design involving adolescent (12-18 years) patients with a diagnosed sport/recreation-related concussion with vestibular symptoms/impairment from a concussion-specialty clinic between October 2018 and February 2020. Eligible participants were randomized in a 1:1 to either a 4-week vestibular intervention group (VESTIB) or a behavioral management control group (CONTROL). CONTROLS (n = 25) were prescribed behavioral management strategies (eg, physical activity, sleep, hydration, nutrition, stress management) and instructed to perform stretching/physical activity (eg, walking, stationary cycle) 30 minutes/day. VESTIB (n = 25) were prescribed precision vestibular rehabilitation exercises and instructed to perform at-home exercises for 30 minutes/day. Primary outcomes were improvement in Vestibular/Ocular Motor Screening vestibular items (ie, horizontal/vertical vestibular-ocular reflex, visual motion sensitivity) at 4 weeks postenrollment.

RESULTS

We screened 310 and enrolled a total of 55 (18%) adolescent patients who were randomized to one of the interventions. Fifty of fifty-five (91%) participants completed all aspects of the study protocol. Participants in VESTIB improved significantly across the intervention period in horizontal (mean difference-1.628; 95% CI [-3.20, -0.06]; P = .04) and vertical (mean difference-2.24; 95% CI [-4.01, -0.48]; P = .01) vestibular-ocular reflex, but not visual motion sensitivity (mean difference-2.03; 95% CI [-4.26, 0.19]) of the Vestibular/Ocular Motor Screening score compared with CONTROLS.

CONCLUSIONS

Overall, the vestibular intervention group experienced greater clinical improvements in vestibular symptoms/impairment than controls across the 4-week intervention.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT03555370.

Effects of Music Intervention on Stress in Concussed and Non-Concussed Athletes

Sport-related concussion is a serious public health issue affecting millions of individuals each year. Among the many negative side effects, emotional symptoms, such as stress, are some of the most common. Stress management is repeatedly cited by expert groups as an important intervention for this population. It was shown that music has relaxing effects, reducing stress through the activation of brain areas involved in emotions and pleasure. The objective of this study was to explore the effects of a music-listening intervention compared with silence on experimentally induced stress in concussed and non-concussed athletes. To this aim, four groups of athletes (non-concussed music, non-concussed silence, concussed music, and concussed silence) performed the Trier Social Stress Test, for which both physiological (skin conductance level) and self-reported stress measurements were taken. No significant difference was found in the pattern of stress recovery for self-reported measurements. However, the skin conductance results showed greater and faster post-stress recovery after listening to music compared with silence for concussed athletes only. Taken together, these results suggest that music could be an efficient stress management tool to implement in the everyday life of concussed athletes to help them prevent stress accumulation.

Insufficient sampling frequencies skew heart rate variability estimates: Implications for extracting heart rate metrics from neuroimaging and physiological data

BACKGROUND

While cardiac pulsations are widely present within physiological and neuroimaging data, it is unknown the extent this information can provide valid and reliable heart rate and heart rate variability (HRV) estimates. The objective of this study was to demonstrate how a slight temporal shift due to an insufficient sampling frequency can impact the validity/accuracy of deriving cardiac metrics.

METHODS

Twenty-two participants were instrumented with valid/reliable industry-standard or open-source electrocardiograms. Five-minute lead II recordings were collected at 1000 Hz in an upright orthostatic position. Following artifact removal, the 1000 Hz recording for each participant was downsampled to frequencies ranging 2-500 Hz. The validity of each participant's downsampled recording was compared against their 1000 Hz recording ("reference-standard") using Bland-Altman plots with 95 % limits of agreement (LOA), coefficient of variation (CoV), intraclass correlation coefficients, and adjusted r-squared values.

RESULTS

Downsampled frequencies of ≥ 50 and ≥ 90 Hz produced highly robust measures with narrow log-transformed 95 % LOA (<±0.01) and low CoV values (≤3.5 %) for heart rate and HRV metrics, respectively. Below these thresholds, the log-transformed 95 % LOA became wider (LOA range: ±0.1-1.9) and more variable (CoV range: 1.5-111.6 %).

CONCLUSION

These results provide an important consideration for obtaining cardiac information from physiological data. Compared to the "reference-standard" ECG, a seemingly negligible temporal shift of the systolic contraction (R wave) greater than 11-milliseconds (90 Hz) away from its true value, lessened the validity of the HRV. Further research is warranted to determine the minimum sampling frequency required to obtain valid heart rate/HRV metrics from pulsatile waveforms.

Alterations in Urine Metabolomics Following Sport-Related Concussion: A 1H NMR-Based Analysis

Objective: Millions of sport-related concussions (SRC) occur annually in North America, and current diagnosis of concussion is based largely on clinical evaluations. The objective of this study was to determine whether urinary metabolites are significantly altered post-SRC compared to pre-injury.

Setting: Outpatient sports medicine clinic.

Participants: Twenty-six male youth sport participants.

Methods: Urine was analyzed pre-injury and after SRC by ¹H NMR spectroscopy. Data were analyzed using multivariate statistics, pairwise t-test, and metabolic pathway analysis. Variable importance analysis based on random variable combination (VIAVC) was applied to the entire data set and resulted in a panel of 18 features. Partial least square discriminant analysis was performed exploring the separation between pre-injury and post-SRC groups. Pathway topography analysis was completed to identify biological pathway involvement. Spearman correlations provide support for the relationships between symptom burden and length of return to play and quantifiable metabolic changes in the human urinary metabolome.

Results: Phenylalanine and 3-indoxysulfate were upregulated, while citrate, propylene glycol, 1-methylhistidine, 3-methylhistidine, anserine, and carnosine were downregulated following SRC. A receiver operator curve (ROC) tool constructed using the 18-feature classifier had an area under the curve (AUC) of 0.887. A pairwise t-test found an additional 19 altered features, 7 of which overlapped with the VIAVC analysis. Pathway topology analysis indicated that aminoacyl-tRNA biosynthesis and beta-alanine metabolism were the two pathways most significantly changed. There was a significant positive correlation between post-SRC 2-hydroxybutyrate and the length of return to play (ρ = 0.482, p = 0.02) as well as the number of symptoms and post-SRC lactose (ρ = 0.422, p = 0.036).

Conclusion: We found that ¹H NMR metabolomic urinary analysis can identify a set of metabolites that can correctly classify SRC with an accuracy of 81.6%, suggesting potential for a more objective method of characterizing SRC. Correlations to both the number of symptoms and length of return to play indicated that 2-hydroxybutyrate and lactose may have potential applications as biomarkers for sport-related concussion.

Cardiovascular Sequalae of Sports-Related Concussions

We are becoming more aware of sports-related concussions (SRCs). Current return-to-play (RTP) guidelines are often based on subjective clinical symptoms rather than objective physiologic measures. Although evidence is limited, the purpose of this manuscript is to summarize the data pertaining to acute and chronic cardiovascular effects of SRCs, and to determine whether there are objective metrics that could improve currently used RTP protocols. Research shows that SRCs cause cardiovascular autonomic nervous system (CV-ANS) dysfunction induced by decreased baroreceptor sensitivity (BRS). This disturbance persists past the point of clinical symptom resolution and can worsen through subsequent exertion, which may impact long-term recovery. Further studies are needed to establish the most appropriate physiologic metrics for analyzing recovery post-SRC and whether the addition of physiologic measures to RTP guidelines improves recovery from these injuries. This is an understudied area that carries important clinical implications. Larger and more robust trials are warranted to inform the development of guidelines that should focus on lessening the compounding effects of multiple concussions and improve the management of SRCs. This article is protected by copyright. All rights reserved.

Should We Lose Sleep Over Sleep Disturbances After Sports-Related Concussion? A Scoping Review of the Literature

OBJECTIVE

A single, severe traumatic brain injury can result in chronic sleep disturbances that can persist several years after the incident. In contrast, it is unclear whether there are sleep disturbances after a sports-related concussion (SRC). Considering growing evidence of links between sleep disturbance and neurodegeneration, this review examined the potential links between diagnosed SRCs and sleep disturbances to provide guidance for future studies.

METHODS

The scoping review undertook a systematic search of key online databases (Scopus, MEDLINE, SportDiscus, and Web of Science) using predetermined search terms for any articles that examined sleep after concussion. A screening criterion using agreed inclusion and exclusion criteria was utilized to ensure inclusion of relevant articles.

DESIGN

This scoping review is guided by the PRSIMA Scoping Review report.

RESULTS

Ten studies met the inclusion criteria, reporting on 896 adults who had experienced an SRC. Comparison with 1327 non-SRC adults occurred in 8 studies. Nine studies subjectively examined sleep, of which all but one study reported sleep disturbances after an SRC. Three studies objectively measured sleep, with 2 studies indicating large coefficients of variation of sleep duration, suggesting a range of sleep responses after an SRC. The only study to examine overnight polysomnography showed no differences in sleep metrics between those with and without an SRC. No studies examined interventions to improve sleep outcomes in people with concussion.

CONCLUSIONS

This scoping review indicates preliminary evidence of sleep disturbances following an SRC. The heterogeneity of methodology used in the included studies makes consensus on the results difficult. Given the mediating role of sleep in neurodegenerative disorders, further research is needed to identify physiological correlates and pathological mechanisms of sleep disturbances in SRC-related neurodegeneration and whether interventions for sleep problems improve recovery from concussion and reduce the risk of SRC-related neurodegeneration.

Autonomic Dysregulation in Adolescent Concussion Is Sex- and Posture-Dependent

OBJECTIVE

To study autonomic responses to postural changes in concussed adolescents. The influence of sex was also studied.

DESIGN

Longitudinal cohort observational study.

PARTICIPANTS

Concussed adolescents (CONC; n = 65; 26 male adolescents; age 15 ± 1 years, range = 12-18 years) and a control (CTRL) group of nonconcussed adolescents of similar age and sport (CTRL; n = 54; 29 male adolescents; age 14 ± 1 years, range = 12-18 years).

INTERVENTIONS

Concussed participants were monitored through 6 weekly visits throughout usual physician care. Control participants underwent 2 visits separated by at least 1 week to account for intrapersonal variation in testing measures.

MAIN OUTCOME MEASURES

Heart rate variability as the root mean square of successive differences in R-R intervals (RMSSD), heart rate (HR), and blood pressure [mean arterial pressure (MAP) and diastolic blood pressure (DBP)] were measured in supine, sitting, and standing postures.

RESULTS

A mixed analysis of variance revealed a group × sex × posture interaction (P = 0.04) where seated values of RMSSD were less in concussed female participants versus control female participants (42 ± 4 vs 61 ± 7 ms; P = 0.01; Mann-Whitney rank test). Compared with CTRL, CONC exhibited increased pretesting seated DBP (69 ± 1 vs 74 ± 1 mm Hg; P < 0.01), MAP (83 ± 1 vs 86 ± 1 mm Hg; P = 0.02), and baseline seated HR (72 ± 1 vs 77 ± 2 bpm; P = 0.03). Values of DBP (P = 0.03) and MAP (P < 0.01) improved at clinical discharge, whereas the RMSSD in female participants did not (P > 0.5). Data are mean ± SEM.

CONCLUSIONS

A modest reduction in female cardiac autonomic regulation was observed during seated postures. Alterations in seated concussed DBP and MAP, but not RMSSD, resolved at clinical discharge (median = 37 days). The results indicate that, in adolescents, concussion may impair cardiovagal function in a sex- and posture-dependent manner. The findings also suggest that BP metrics, but not RMSSD, are associated with clinical concussion recovery.

The validity and reliability of ultra-short-term heart rate variability parameters and the influence of physiological covariates

Ultra-short-term (UST) heart rate variability (HRV) metrics have increasingly been proposed as surrogates for short-term HRV metrics. However, the concurrent validity, within-day reliability, and between-day reliability of UST HRV have yet to be comprehensively documented. Thirty-six adults (18 males, age: 26 ± 5 yr, BMI: 24 ± 3 kg/m²) were recruited. Measures of HRV were quantified in a quiet-stance upright orthostatic position via three-lead electrocardiogram (ADInstruments, FE232 BioAmp). All short-term data recordings were 300 s in length and five UST time points (i.e., 30 s, 60 s, 120 s, 180 s, and 240 s) were extracted from the original 300-s recording. Bland-Altman plots with 95% limits of agreement, repeated measures ANOVA and two-tailed paired t tests demarcated differences between UST and short-term recordings. Linear regressions, coefficient of variation, intraclass correlation coefficients, and other tests examined the validity and reliability in both time- and frequency domains. No group differences were noted between all short-term and UST measures, for either time- (all P > 0.202) or frequency-domain metrics (all P > 0.086). A longer recording duration was associated with augmented validity and reliability, which was less impacted by confounding influences from physiological variables (e.g., respiration rate, carbon dioxide end-tidals, and blood pressure). Conclusively, heart rate, time-domain, and relative frequency-domain HRV metrics were acceptable with recordings greater or equal to 60 s, 240 s, and 300 s, respectively. Future studies employing UST HRV metrics should thoroughly understand the methodological requirements to obtain accurate results. Moreover, a conservative approach should be utilized regarding the minimum acceptable recording duration, which ensures valid/reliable HRV estimates are obtained.NEW & NOTEWORTHY A one size fits all methodological approach to quantify HRV metrics appears to be inappropriate, where study design considerations need to be conducted upon a variable-by-variable basis. The present results found 60 s (heart rate), 240 s (time-domain parameters), and 300 s (relative frequency-domain parameters) were required to obtain accurate and reproducible metrics. The lower validity/reliability of the ultra-short-term metrics was attributable to measurement error and/or confounding from extraneous physiological influences (i.e., respiratory and hemodynamic variables).

Rehabilitation of Concussion and Persistent Postconcussive Symptoms

Concussion and persistent postconcussive symptoms (PPCS) are encountered by clinicians in sports medicine, pediatrics, neurology, physiatry, emergency medicine, and primary care. Clinical management may require a multidisciplinary approach. This article presents a structured method for the diagnosis of concussion and PPCS in the outpatient setting, which includes a history, physical examination, and additional tests as clinically indicated to help identify underlying symptom generators. Treatment for concussion and PPCS should be individualized, based on predominant signs and symptoms, and can include subsymptom threshold aerobic exercise, cervical physical therapy, vestibulo-ocular rehabilitation, behavioral and cognitive psychotherapy, and some symptom-specific pharmacological therapies.

Detailed description of Division I ice hockey concussions: Findings from the NCAA and Department of Defense CARE Consortium

OBJECTIVE

Since concussion is the most common injury in ice hockey, the objective of the current study was to elucidate risk factors, specific mechanisms, and clinical presentations of concussion in men's and women's ice hockey.

METHODS

Ice hockey players from 5 institutions participating in the Concussion Assessment, Research, and Education Consortium were eligible for the current study. Participants who sustained a concussion outside of this sport were excluded. There were 332 (250 males, 82 females) athletes who participated in ice hockey, and 47 (36 males, 11 females) who sustained a concussion.

RESULTS

Previous concussion (odds ratio (OR) = 2.00; 95% confidence interval (95% CI): 1.02‒3.91) was associated with increased incident concussion odds, while wearing a mouthguard was protective against incident concussion (OR = 0.43; 95%CI: 0.22‒0.85). Overall, concussion mechanisms did not significantly differ between sexes. There were specific differences in how concussions presented clinically across male and female ice hockey players, however. Females (9.09%) were less likely than males (41.67%) to have a delayed symptom onset (p = 0.045). Additionally, females took significantly longer to reach asymptomatic (p = 0.015) and return-to-play clearance (p = 0.005). Within the first 2 weeks post-concussion, 86.11% of males reached asymptomatic, while only 45.50% of females reached the same phase of recovery. Most males (91.67%) were cleared for return to play within 3 weeks of their concussion, compared to less than half (45.50%) of females.

CONCLUSION

The current study proposes possible risk factors, mechanisms, and clinical profiles to be validated in future concussions studies with larger female sample sizes. Understanding specific risk factors, concussion mechanisms, and clinical profiles of concussion in collegiate ice hockey may generate ideas for future concussion prevention or intervention studies.

Mood, Psychological, and Behavioral Factors of Health-Related Quality of Life Throughout Recovery From Sport Concussion

OBJECTIVE

To measure alterations in mood, psychological, and behavioral factors in collegiate athletes throughout recovery from sport concussion (SC) compared with matched controls.

SETTING

University research laboratory.

PARTICIPANTS

Twenty (55% female) division I collegiate athletes with SC (19.3 ± 1.08 years old, 1.77 ± 0.11 m, 79.6 ± 23.37 kg) and 20 (55% female) uninjured matched controls (20.8 ± 2.17 years old, 1.77 ± 0.10 m, 81.9 ± 23.45 kg).

DESIGN

Longitudinal case control.

MAIN MEASURES

Self-reported concussion-related symptoms, anxiety, resilience, stigma, sleep disturbance, fatigue, and appetite were assessed at 3 time points in the SC group: T1 (≤72 hours of SC), T2 (7 days after T1), and TF (after symptom resolution). Control participants were evaluated at similar intervals. Group and group-by-sex differences were assessed using repeated-measures analyses of variance. Post hoc analyses were performed with Tukey's honestly significant difference (HSD) and paired-sample t tests.

RESULTS

The SC group had greater sleep disturbance than controls at T1 (P = .001; d = 1.21) and endorsed greater stigma at all time points (P ≤ .03; d ≥ 0.80). Stigma (F(2) = 3.68; P = 0.03; η2p = 0.12), sleep disturbance (F(2) = 5.27; P = .008; η2p = 0.15), and fatigue (F(2) = 3.46; P = .04; η2p = 0.11) improved throughout recovery in those with SC only. No differences were observed between males and females (P > .05).

CONCLUSION

Sleep disturbance and stigma were negatively affected by SC, highlighting potential areas for clinical interventions to maximize recovery in males and females.

Cardiorespiratory Functioning in Youth with Persistent Post-Concussion Symptoms: A Pilot Study

Dysregulation of the autonomic nervous system (ANS) may play an important role in the development and maintenance of persistent post-concussive symptoms (PPCS). Post-injury breathing dysfunction, which is influenced by the ANS, has not been well-studied in youth. This study evaluated cardiorespiratory functioning at baseline in youth patients with PPCS and examined the relationship of cardiorespiratory variables with neurobehavioral outcomes. Participants were between the ages of 13-25 in two groups: (1) Patients with PPCS (concussion within the past 2-16 months; n = 13) and (2) non-injured controls (n = 12). Capnometry was used to obtain end-tidal CO2 (EtCO2), oxygen saturation (SaO2), respiration rate (RR), and pulse rate (PR) at seated rest. PPCS participants exhibited a reduced mean value of EtCO2 in exhaled breath (M = 36.3 mmHg, SD = 2.86 mmHg) and an altered inter-correlation between EtCO2 and RR compared to controls. Neurobehavioral outcomes including depression, severity of self-reported concussion symptoms, cognitive catastrophizing, and psychomotor processing speed were correlated with cardiorespiratory variables when the groups were combined. Overall, results from this study suggest that breathing dynamics may be altered in youth with PPCS and that cardiorespiratory outcomes could be related to a dimension of neurobehavioral outcomes associated with poorer recovery from concussion.

The Influence of Family History of Neurodegenerative Disease on Adolescent Concussion Outcomes

Evidence suggests that factors associated with a family history of neurodegenerative disease (fhNDD) may influence outcomes following a concussion. However, the relevance of these findings in adolescent populations has not been fully explored. Therefore, the present study sought to evaluate the relationship between fhNDD and neurological outcomes following an adolescent concussion. Data from a local pediatric concussion clinic were used to compare adolescents with (n = 22) and without (n = 44) an fhNDD. Clinical symptom burden, emotional health, cardio-autonomic function, and cognitive performance were assessed at initial (~2 weeks) and follow-up (~5 weeks) post-injury evaluations. Cardio-autonomic function was assessed at rest and during isometric handgrip contraction (IHGC). Results indicated no significant group differences in emotional health or cognitive performance. Across evaluations, those with an fhNDD exhibited greater somatic symptom severity, alterations in HRV at rest, and early blunted cardio-autonomic reactivity during IHGC compared to those without an fhNDD. These findings suggest that positive fhNDD is negatively associated with clinical symptomology and cardio-autonomic functioning following an adolescent concussion. Further, these findings encourage clinicians to utilize a comprehensive neurological evaluation to monitor concussion recovery. Future studies should look into exploring the role of specific neurodegenerative processes and conditions on concussion outcomes in adolescents.

O uso da análise da variabilidade da frequência cardíaca no monitoramento de lesões esportivas e sua influência sobre o balanço autonômico: uma revisão sistemática

RESUMO O objetivo desta revisão busca compreender o uso da variabilidade da frequência cardíaca (VFC) para identificar sua relação com a ocorrência de lesões esportivas que não envolvem contato, além de indicar padrões da VFC após concussões para orientar o retorno seguro ao esporte. Foi realizada uma revisão sistemática nas bases de dados Pubmed, EMBASE e PEDRo, incluindo artigos até dezembro de 2020, utilizando os seguintes termos: ((((athletes OR players) AND (Heart Hate Variability OR HRV)) AND (sport OR sports OR exercises OR physical activity)) AND (injuries OR injury)). Os princípios de elegibilidade de PICOS foram: P (population): atletas, I (intervention): o uso da VFC, C (control): atletas não lesionados, O (outcomes): índices de VFC e suas relações com lesões esportivas, e S (study): estudos em seres humanos. De 62 artigos identificados na busca, 12 foram incluídos na revisão, sendo 6 mostrando que a diminuição da VFC e o desequilíbrio simpatovagal estão relacionados à fadiga, overtraining e overreaching; e 6 artigos relacionados com a avaliação da VFC pós-concussão, onde identificaram alteração de modulação autonômica nos atletas concussionados que vão além da ausência dos sintomas. Em conclusão, a VFC pode ser uma ferramenta utilizada no âmbito esportivo para identificar maior risco de lesões esportivas sem contato, identificando situações de fadiga, overtraining e overreaching, como também auxiliar no processo de retorno ao esporte pós-concussão cerebral pela avaliação do balanço autonômico.

Understanding concussion knowledge and behavior among mixed martial arts, boxing, kickboxing, and Muay Thai athletes and coaches

Objectives: In combat sports, strikes to the head are not just incidental but a deliberate and clear determinant of success. Concussion is a complex injury that is poorly understood and inappropriate practices are often observed among athletes and coaches. The purpose of this study was to investigate concussion knowledge and behavior as well as address recommendations for combat sports athletes and coaches. Methods: 70 athletes and 35 coaches from combat sports disciplines completed an online-validated survey and a personal questionnaire about concussion knowledge, training experience, and knowledge translation. Athletes were divided into subgroups for analysis according to sex (male n = 55, female n = 15), skill level (amateur n = 52, professional n = 18), and weight classes (<66.2 kg: n = 25, 66.6 to 77.5 kg: n = 30, and >78 kg: n = 15). Results: The likely absence of health-care professionals during training was confirmed by 68.5% of coaches, and athletes declared that self-diagnosis (79%) and coaches' diagnosis (43.3%) were the most used method of suspected concussion assessment. Merely 5.7% of coaches properly recognized the level of traumatic brain injury a concussion represents, 68.8% were unfamiliar with any sideline assessment tools, and only 14.3% often seek out concussion knowledge. Athletes who were aware of the level of brain injury a concussion represents performed fewer sparring sessions per week (mild: 1.27 ± 1.1; severe: 3.17 ± 2.81; p = .05, d = .89) and had a greater likelihood of reporting concussive episodes. Most professional (55.5%), female (54.5%), and under 66.2 kg (50%) athletes returned to full practice within 1 week following a concussion diagnosis. Conclusions: Relevant key gaps of knowledge and behavior were verified in combat sports athletes and coaches. The awareness of basic concepts may improve injury reporting and safer behavior in athletes. Knowledge translation strategies with accessible language are recommended for coaches, in particular on how to identify acute symptoms and perform basic assessment.

Evaluating Multiple Domains of Health in High School Athletes With Sport-Related Concussion

CONTEXT

Concussions are shown to hinder multiple health dimensions, including health-related quality of life (HRQOL), suggesting a need for a whole-person approach to assessment and treatment. Patient-reported outcome measures are one method to gather the patient's perspective regarding their HRQOL.

OBJECTIVE

To evaluate perceived HRQOL using the Patient-Reported Outcomes Measurement Information System Pediatric-25 subscale in patients throughout concussion recovery.

DESIGN

Prospective cohort, descriptive survey.

SETTING

There were 9 high school athletic training facilities.

PARTICIPANTS

A total of 70 patients with diagnosed concussions (51 males, 7 females, 12 unreported; age = 15.7 [0.9] y, height = 174.6 [8.4] cm, mass = 72.8 [14.8] kg, grade = 10.0 [0.9] level).

INTERVENTIONS

Patient-Reported Outcomes Measurement Information System Pediatric-25 was administered at 3 days, 10 days postconcussion, and return to play (RTP).

MAIN OUTCOME MEASURES

Patient-Reported Outcomes Measurement Information System Pediatric-25 subscale T scores and self-reported concussion history (yes/no).

RESULTS

A total of 70 patients completed the study. For the Pediatric-25 subscales, the severity of problems associated with Physical Function Mobility, Anxiety, Depression, Fatigue, and Pain Interference were highest 3 days postconcussion, decreasing at 10 days and RTP (all p < .05). No differences were found between days 3 and 10 for Peer Relationship scores, but improvements were identified at RTP (p < .05). Pediatric-25 subscale scores at the 3 measurements were not statistically associated with concussion history (all p > .05). Ceiling and floor effects were present in all subscales throughout each timepoint, except for Physical Function Mobility (14.7%), and pain interference (11.8%) at day 3 postinjury.

CONCLUSIONS

Patients who had suffered a concussion improved from day 3 through RTP on multiple health domains as demonstrated through the Pediatric-25 subscales. These findings highlight the need for health care professionals to serially monitor HRQOL and social factors that may affect the patient postconcussion as part of a multifactorial assessment. Ceiling effects in high functioning adolescent athletes were present; thus, efforts should be made to identify appropriate scales for use in managing recovery in athletic populations.

The relationship between fluid biomarkers and clinical outcomes in sports-related concussions: a systematic review

OBJECTIVES

The literature on fluid biomarkers for concussion has primarily focused on comparing athletes with and without a diagnosis of concussion and on examining the relationship between fluid biomarkers and exposure to head trauma. This systematic literature review aims to examine the strength of evidence for fluid biomarkers to be associated with clinically relevant outcomes in sports-related concussion.

METHODS

A systematic literature review was conducted using EmBASE, PubMed, and CINAHL. English-language articles that included athletes participating in organized sports and reported the relationship between at least one fluid biomarker and at least one clinical outcome measure, or provided data that could be used to analyze this relationship, were included.

RESULTS

Studies of the relationship between fluid biomarkers and clinical outcomes of concussion have yielded small or variable effects. There were significant inconsistencies in methodology including duration of time post-injury of biomarker collection, use of control groups, the number of time points post-injury that biomarkers were collected, and what clinical outcomes were utilized.

CONCLUSION

There is currently insufficient evidence to support a relationship between any of the included fluid biomarkers and clinical outcome measures of concussion. Future research including clinical outcome measures and using standardized study design and methodology is necessary.

Cerebrovascular Reactivity After Sport Concussion: From Acute Injury to 1 Year After Medical Clearance

Neuroimaging has identified significant disturbances in cerebrovascular reactivity (CVR) in the early symptomatic phase of sport-related concussion. However, less is known about how whole-brain alterations in CVR evolve after concussion and whether they remain present beyond medical clearance to return to play (RTP). In the present study, CVR was evaluated using blood-oxygenation-level-dependent functional magnetic resonance imaging (BOLD fMRI) during a respiratory challenge. Imaging data were collected for 110 university-level athletes, including 39 concussed athletes and 71 athletic controls. The concussed athletes were imaged at the acute phase of injury (1–7 days post-injury), the subacute phase (8-14 days post-injury), medical clearance to RTP, 1 month post-RTP, and 1 year post-RTP. Enhanced negative BOLD response to controlled breathing was seen at acute injury, with attenuation of the effect mainly occurring by 1 year post-RTP. Secondary analyses showed that greater symptom severity and prolonged recovery were associated with enhanced BOLD response in the acute phase of injury, but a more attenuated BOLD response in the subacute phase. This study provides novel information characterizing the CVR response after concussion and shows CVR to be a sensitive technique for evaluating long-term brain recovery.

Sex-Related Differences in the Effects of Sports-Related Concussion: A Review

Sports-related concussion is a serious health challenge, and females are at higher risk of sustaining a sports-related concussion compared to males. Although there are many studies that investigate outcomes following concussion, females remain an understudied population, despite representing a large proportion of the organized sports community. In this review, we provide a summary of studies that investigate sex-related differences in outcome following sports-related concussion. Moreover, we provide an introduction to the methods used to study sex-related differences after sports-related concussion, including common clinical and cognitive measures, neuroimaging techniques, as well as biomarkers. A literature search inclusive of articles published to March 2020 was performed using PubMed. The studies were reviewed and discussed with regard to the methods used. Findings from these studies remain mixed with regard to the effect of sex on clinical symptoms, concussion-related alterations in brain structure and function, and recovery trajectories. Nonetheless, there is initial evidence to suggest that sex-related differences following concussion are important to consider in efforts to develop objective biomarkers for the diagnosis and prognosis of concussion. Additional studies on this topic are, however, clearly needed to improve our understanding of sex-related differences following concussion, as well as to understand their neurobiological underpinnings. Such studies will help pave the way toward more personalized clinical management and treatment of sports-related concussion.

Sleep Disturbances in the Acute Stage of Concussion are Associated With Poorer Long-Term Recovery: A Systematic Review

OBJECTIVE

To examine the association between sleep during the acute stage of concussion and long-term outcomes.

LITERATURE SURVEY

Literature searches were performed 1 July 2018 to 1 August 2018 in Ovid MEDLINE, CINAHL, and Web of Science, along with hand searching for gray literature and cited references. Of the 610 search results, 359 unique references were reviewed after duplicates were removed.

METHODOLOGY

Two reviewers independently reviewed and came to consensus on which titles/abstracts met inclusion/exclusion criteria (n = 23). The 23 full-text articles were assessed independently by the same two reviewers for eligibility. Consensus was achieved, leaving four articles for quality assessment and data extraction. One person extracted relevant data from each study using a standard data-extraction table. The data extraction table was reviewed by two reviewers and consensus was achieved for completeness and accuracy. Quality appraisal was conducted to assess the risk for potential bias and quality of included articles.

SYNTHESIS

Two of the articles included children younger than 16 years old and two included a wide age range. In general, poorer sleep was associated with poorer outcomes following concussion at reassessments across any age population. In addition, poorer sleep in the acute stage of concussion was associated with poorer long-term outcomes and recovery.

CONCLUSIONS

The variability in sleep assessments used, symptoms assessed, length of time to reassessments, and comparator group included made data synthesis challenging. The use of standard valid and reliable sleep assessments is recommended. Future studies may consider if addressing sleep disturbances early following concussion will improve longer-term outcomes.

Scale-free functional brain dynamics during recovery from sport-related concussion

Studies using blood‐oxygenation‐level‐dependent functional magnetic resonance imaging (BOLD fMRI) have characterized how the resting brain is affected by concussion. The literature to date, however, has largely focused on measuring changes in the spatial organization of functional brain networks. In the present study, changes in the temporal dynamics of BOLD signals are examined throughout concussion recovery using scaling (or fractal) analysis. Imaging data were collected for 228 university‐level athletes, 61 with concussion and 167 athletic controls. Concussed athletes were scanned at the acute phase of injury (1–7 days postinjury), the subacute phase (8–14 days postinjury), medical clearance to return to sport (RTS), 1 month post‐RTS and 1 year post‐RTS. The wavelet leader multifractal approach was used to assess scaling (c₁) and multifractal (c₂) behavior. Significant longitudinal changes were identified for c₁, which was lowest at acute injury, became significantly elevated at RTS, and returned near control levels by 1 year post‐RTS. No longitudinal changes were identified for c₂. Secondary analyses showed that clinical measures of acute symptom severity and time to RTP were related to longitudinal changes in c₁. Athletes with both higher symptoms and prolonged recovery had elevated c₁ values at RTS, while athletes with higher symptoms but rapid recovery had reduced c₁ at acute injury. This study provides the first evidence for long‐term recovery of BOLD scale‐free brain dynamics after a concussion.

The Changing Landscape of Sport Concussion

It was not too long ago that many people referred to concussion as a “hidden injury” and a “complex injury for which we still had much to learn.” We still have a lot to learn about these injuries, but because of the advancement of concussion research we are better informed today than we were just a decade ago. Much of this work began in the early to mid-1990s with studies aimed at equipping clinicians with better concussion-assessment tools. We needed to remove the guesswork, so more systematic and objective concussion-assessment batteries (sideline and clinic) that included symptom checklists, cognitive tests, and balance assessments were developed and validated. As a result, it became easier to detect and/or rule out concussions and to track recovery for several days postinjury. From 2009 through 2014, all 50 states and the District of Columbia passed concussion legislation requiring concussion education for high school and youth athletes, among other things. This was a critical period in which more emphasis was placed on concussion prevention, ultimately leading to increased reporting of these injuries and a reduction in the number of unreported and undiagnosed concussions. More recently, the corpus of science has evolved to identify potential blood and neuroimaging biomarkers to complement the traditional-clinical assessment tools, and newer studies are focused on treatment after concussion—challenging the notions that “rest is best” and that the effects of concussion are permanent and immutable. The research is ongoing, and several large multisite studies will yield important findings to help guide clinical decision making in the next few years.