Interaction of obesity and proteins associated with the NLRP3 inflammasome following mild traumatic brain injury

The NOD-like receptor pyrin domain-containing protein 3 (NLRP3) inflammasome has been associated with worse outcomes from severe traumatic brain injury (TBI). The NLRP3 inflammasome is also strongly associated with other pro-inflammatory conditions, such as obesity. Little is known about the potential effect of mild TBI (mTBI) on the NLRP3 inflammasome and the extent to which modifying factors, such as obesity, may augment the inflammatory response to mTBI. The purpose of this study was to evaluate the association of NLRP3 inflammasome proteins with obese body mass index (BMI ≥ 30) within 24 h of mTBI after presenting to a level 1 trauma center emergency department. This is a secondary analysis of prospectively enrolled patients with mTBI who presented to the emergency department of one U.S. Level 1 trauma center from 2013 to 2018 (n = 243). A series of regression models were built to evaluate the association of NLRP3 proteins obtained from blood plasma within 24 h of injury and BMI as well as the potential interaction effect of higher BMI with NLRP3 proteins (n = 243). A logistic regression model revealed a significant association between IL-18 (p < 0.001) in mTBI patients with obese BMI compared to mTBI patients with non-obese BMI (< 30). Moderation analyses revealed statistically significant interaction effects between apoptotic speck-like protein (ASC), caspase-1, IL-18, IL-1β and obese BMI which worsened symptom burden, quality of life, and physical function at 2 weeks and 6 months post-injury. Higher acute concentrations of IL-1β in the overall cohort predicted higher symptoms at 6-months and worse physical function at 2-weeks and 6-months. Higher acute concentrations of IL-18 in the overall cohort predicted worse physical function at 6-months. In this single center mTBI cohort, obese BMI interacted with higher acute concentrations of NLRP3 inflammasome proteins and worsened short- and long-term clinical outcomes.

The Interval Between Concussions Does Not Influence Time to Asymptomatic or Return to Play: A CARE Consortium Study

INTRODUCTION

The purpose of this study was to determine if the time interval between two concussive events influences the number of days to asymptomatic status, days to return to play, or performance on common post-concussion assessments following the second concussion.

METHODS

Data from 448 collegiate athletes and service academy cadets with two concussions (time between concussions: median 295.0 days [interquartile range: 125.0-438.2]), 40.0% female) were analyzed from Concussion Assessment Research and Education (CARE) Consortium institutions between 2014 and 2020. Days between concussions was the primary predictor variable. Primary outcome measures included time to asymptomatic and time to return to play following the second concussion. Secondary outcome measures included total number of symptoms, total symptom severity, Balance Error Scoring System total score, and Standardized Assessment of Concussion total score within 48 h of their second concussion.

RESULTS

Time between concussions did not significantly contribute to the multivariate time to asymptomatic (p = 0.390), time to return to play (p = 0.859), or the secondary outcomes (p-range = 0.165-0.477) models. Time to asymptomatic (p = 0.619) or return to play (p = 0.524) did not differ between same-season and different-season concussions. Sex significantly contributed to the return to play (p = 0.005) multivariate model. Delayed symptom onset and immediate removal from play/competition significantly contributed to the total number of symptoms (p = 0.001, p = 0.014) and symptom severity (p = 0.011, p = 0.022) multivariate models.

CONCLUSION

These results suggest that in a population with a large period between injuries, the time between concussions may not be relevant to clinical recovery.

Medical Conditions in Former Professional American-Style Football Players Are Associated With Self-Reported Clinical Features of Traumatic Encephalopathy Syndrome

Consensus criteria for traumatic encephalopathy syndrome (TES) specify that at least one core clinical feature of cognitive impairment (CI; e.g., difficulties with memory, executive function) or neurobehavioral dysregulation (ND; e.g., explosiveness, rage, and mood lability) be present and not fully accounted for by other health disorders. Associations between self-reported symptoms that mirror the core clinical features of TES-and how they may be related to concomitant medical conditions-remain unclear. The purpose of this study was to evaluate the association of medical conditions and football exposures with TES clinical features (CI+/-, ND+/-) in 1741 former professional American-style football (ASF) players (age, 57.7 ± 13.9 years; professional seasons, 6.6 ± 3.9 years). Demographics (age, race/ethnicity, current body mass index, age of first football exposure, use of performance-enhancing drugs, position played, and past concussion symptoms), self-reported medical conditions (anxiety, depression, attention-deficit hyperactivity disorder [ADHD], sleep apnea, headache, stroke, hypertension, heart disease, high cholesterol, erectile dysfunction, and low testosterone) were collected. Of 1741 participants, 7.4% were CI+ and/or ND+ (n = 129). Participants who were CI+ or ND+ were more likely to report one or more coexisting medical conditions than participants who did not report CI or ND (odds ratio [OR] = 2.04; 95% confidence interval: 1.25-3.47; p = 0.003). Separate general linear models for each medical condition that adjusted for demographics and football-related factors identified significant associations between ADHD, diabetes, erectile dysfunction, headaches, sleep apnea, anxiety, and low testosterone and CI+ and/or ND+ (ORs = 1.8-6.0). Chi-square automatic interaction detection (CHAID) multi-variable decision tree models that incorporated medical conditions and football exposures accurately differentiated former players meeting either CI or ND clinical criteria from those meeting none (accuracy = 91.2-96.6%). CHAID identified combinations of depression, headache, sleep apnea, ADHD, and upper quartiles of concussion symptom history as most predictive of CI+ and/or ND+ status. CI+ and/or ND+ players were more likely to report medical conditions known to cause cognitive symptoms. Concussion exposure and medical conditions significantly increased the likelihood that a former ASF player would demonstrate cognitive or neurobehavioral dysfunction. Clinicians engaged with this population should consider whether treatable coexisting condition(s) could account for some portion of the clinical picture associated with TES presentation.

Evaluating Recovery After Two and Three Repeated Concussions Using Growth Curves

The results of prior research concerning the effects of repeated concussions have been mixed. The aim of this study was to evaluate how concussion outcomes and presentation changed within patients who were evaluated at a concussion specialty clinic multiple times with a concussion. Subjects included 202 patients (54% male) aged 10-21 years (M = 13.17) who presented to a specialty concussion clinic for two and three concussions (77% sport-related) and were followed through formal clearance. First, growth curve models were estimated to determine recovery time and initial symptom burden across the multiple injuries. Second, covariates were added to these models to evaluate which demographic, risk factor, or injury variables predicted any change that did occur in evaluation or outcome variables. Models indicated that each subsequent concussion linearly resulted in significantly fewer days to recovery (-4.62 days, p < 0.047) across three concussions, and significantly lower (and linear) symptom scores on the post-concussion symptom scale (PCSS) (-2.16, p = 0.05). More severe presentation (i.e., days to recovery; higher symptom score) was significantly associated (-.62, p = 0.005) with greater improvement in recovery time (-.62, p = 0.005) and symptom burden (-.56, p < 0.001) at subsequent injuries. No covariates were significantly associated with improvement (or lack thereof) at subsequent injuries. This study adds to evidence suggesting multiple injuries is not associated with protracted recovery at subsequent injuries, in the context of treatment and full clearance for each injury at a multi-disciplinary clinic.

Temporal Changes in Fixational Eye Movements After Concussion in Adolescents and Adults: Preliminary Findings

Concussions often involve ocular impairment and symptoms such as convergence insufficiency, accommodative insufficiency, blurred vision, diplopia, eye strain, and pain. Current clinical assessments of ocular function and symptoms rely on subjective symptom reporting and/or involve lengthy administration time. More objective, brief assessments of ocular function following concussion are warranted. The purpose of this study was to evaluate changes in fixational eye movements (FEMs) and their association with clinical outcomes including recovery time, symptoms, cognitive and vestibular/ocular motor impairment. Thirty-three athletes (13-27 years of age; 54.5% female) within 21 days of a diagnosed concussion participated in the study. A tracking scanning laser ophthalmoscope (TSLO) evaluated FEMs metrics during fixation on a center and corner target. Participants completed symptom (Post-Concussion Symptom Scale [PCSS]), cognitive (Immediate Post-concussion Assessment and Cognitive Testing [ImPACT], and Vestibular/Ocular Motor Screening (VOMS) evaluations. All measures were administered at the initial visit and following medical clearance, which was defined as clinical recovery. Changes in FEMs were calculated using paired-samples t tests. Linear regression (LR) models were used to evaluate the association of FEMs with clinical recovery. Pearson product-moment correlations were used to evaluate the associations among FEMs and clinical outcomes. On the center task, changes across time were supported for average microsaccade amplitude (p = 0.005; Cohen's d = 0.53), peak velocity of microsaccades (p = 0.01; d = 0.48), peak acceleration of microsaccades (p = 0.02; d = 0.48), duration of microsaccade (p < 0.001; d = 0.72), and drift vertical (p = 0.017; d = -0.154). The LR model for clinical recovery was significant (R2 = 0.37; p = 0.023) and retained average instantaneous drift amplitude (β = 0.547) and peak acceleration of microsaccade (β = 0.414). On the corner task, changes across time were supported for drift proportion (p = 0.03; d = 0.43). The LR model to predict clinical recovery was significant (R2 = 0.85; p = 0.004) and retained average amplitude of microsaccades (β = 2.66), peak velocity of microsaccades (β = -15.11), peak acceleration of microsaccades (β = 12.56), drift horizontal (β = 7.95), drift vertical (β = 1.29), drift amplitude (β = -8.34), drift proportion (β = 0.584), instantaneous drift direction (β = -0.26), and instantaneous drift amplitude (β = 0.819). FEMs metrics were also associated with reports of nausea and performance within the domain of visual memory. The FEMs metric were also associated with PCSS, ImPACT, and VOMS clinical concussion outcomes, with the highest magnitude correlations between average saccade amplitude and VOMS symptoms of nausea and average instantaneous drift speed and ImPACT visual memory, respectively. FEMs metrics changed across time following concussion, were useful in predicting clinical recovery, and were correlated with clinical outcomes. FEMs measurements may provide objective data to augment clinical assessments and inform prognosis following this injury.

Network analysis and relationship of symptom factors to functional outcomes and quality of life following mild traumatic brain injury: a TRACK-TBI study

Introduction

Mild traumatic brain injury (mTBI) is a heterogenous injury which can be difficult to characterize and manage. Using cross-sectional network analysis (NA) to conceptualize mTBI symptoms offers an innovative solution to identify how mTBI symptoms relate to each other. The centrality hypothesis of network theory posits that certain symptoms in a network are more relevant (central) or have above average influence over the rest of the network. However, no studies have used NA to characterize the interrelationships between symptoms in a cohort of patients who presented with mTBI to a U.S. Level 1 trauma center emergency department and how subacute central symptoms relate to long-term outcomes.

Methods

Patients with mTBI (Glasgow Coma Scale = 13-15) evaluated across 18 U.S. Level 1 trauma centers from 2013 to 2019 completed the Rivermead Post-Concussion Symptoms Questionnaire (RPQ) at 2 weeks (W2) post-injury (n = 1,593) and at 3 months (M3), 6 months (M6), and 12 months (M12) post-injury. Network maps were developed from RPQ subscale scores at each timepoint. RPQ scores at W2 were associated with M6 and M12 functional and quality of life outcomes.

Results

Network structure did not differ across timepoints, indicating no difference in symptoms/factors influence on the overall symptom network across time. The cognitive factor had the highest expected influence at W2 (1.761), M3 (1.245), and M6 (1.349). Fatigue had the highest expected influence at M12 (1.275). The emotional factor was the only other node with expected influence >1 at any timepoint, indicating disproportionate influence of emotional symptoms on overall symptom burden (M3 = 1.011; M6 = 1.076).

Discussion

Several symptom factors at 2-weeks post-injury were more strongly associated with incomplete recovery and/or poorer injury-related quality of life at 6 and 12 months post-injury than previously validated demographic and clinical covariates. The network analysis suggests that emotional, cognitive, and fatigue symptoms may be useful treatment targets in this population due to high centrality and activating potential of the overall symptom network.

Comparison of physiological outcomes after dynamic exertion between athletes at return to sport from concussion and controls: Preliminary findings

OBJECTIVES

Compare physiological (heart rate, heart rate variability, and blood pressure), performance (change-of-direction task completion time and errors), and clinical (symptoms and rating of perceived exertion) outcomes during dynamic exertion between athletes at return to sport after concussion to healthy athlete controls.

DESIGN

Case control.

METHODS

A sample of 23 (Female = 10; 43.5 %) athletes at medical clearance to play/activity from concussion (CONCUSS) and 23 sex-, age-, and sport-matched healthy athletes (CONTROLS) completed a 5-min seated rest before and after the dynamic exertion test. Independent sample t-tests were used to compare CONCUSS and CONTROLS for completion time, heart rate, and blood pressure; and Mann-Whitney U tests for symptoms, perceived exertion, and errors. A series of ANOVAs were conducted to compare heart rate variability between groups across pre- and post-exercise rest periods.

RESULTS

There were no differences in heart rate, blood pressure, symptoms, perceived exertion, and errors. CONCUSS were faster on Zig Zag (p = .048) and Pro Agility (p = .018) tasks, reported lower symptom severity (p = .019), and had lower post-EXiT HRV (p < .049) than CONTROLS.

CONCLUSIONS

Performance, symptoms, perceived exertion, and blood pressure outcomes from dynamic exertion were equivocal between athletes at medical clearance from concussion and healthy controls, which provide empirical support for dynamic exercise to inform medical clearance clinical decision making for sport-related concussion. However, differences in autonomic nervous system functioning indicate that additional research is needed to examine temporal changes in heart rate variability and other physiological outcomes following dynamic exertion.

The Effects of Rest on Concussion Symptom Resolution and Recovery Time: A Meta-analytic Review and Subgroup Analysis of 4329 Patients

BACKGROUND

Numerous individual studies suggest that rest may have a negative effect on outcomes following concussion.

PURPOSE

To perform a systematic meta-analysis of the effects of prescribed rest compared with active interventions after concussion.

STUDY DESIGN

Meta-analysis; Level of evidence, 4.

METHODS

A meta-analysis (using the Hedges g) of randomized controlled trials and cohort studies was conducted to evaluate the effects of prescribed rest on symptoms and recovery time after concussion. Subgroup analyses were performed for methodological, study, and sample characteristics. Data sources were obtained from systematic search of key terms using Ovid Medline, Embase, Cochrane Database of Systematic Reviews, APA PsycINFO, Web of Science, SPORTDiscus, and ProQuest dissertations and theses through May 28, 2021. Eligible studies were those that (1) assessed concussion or mild traumatic brain injury; (2) included symptoms or days to recovery for ≥2 time points; (3) included 2 groups with 1 group assigned to rest; and (4) were written in the English language.

RESULTS

In total, 19 studies involving 4239 participants met criteria. Prescribed rest had a significant negative effect on symptoms (k = 15; g = -0.27; SE = 0.11; 95% CI, -0.48 to -0.05; P = .04) but not on recovery time (k = 8; g = -0.16; SE = 0.21; 95% CI, -0.57 to 0.26; P = .03). Subgroup analyses suggested that studies with shorter duration (<28 days) (g = -0.46; k = 5), studies involving youth (g = -0.33; k = 12), and studies focused on sport-related concussion (g = -0.38; k = 8) reported higher effect sizes.

CONCLUSION

The findings support a small negative effect for prescribed rest on symptoms after concussion. Younger age and sport-related mechanisms of injury were associated with a greater negative effect size. However, the lack of support for an effect for recovery time and the relatively small overall numbers of eligible studies highlight ongoing concerns regarding the quantity and rigor of clinical trials in concussion.

REGISTRATION

CRD42021253060 (PROSPERO).

Association of obesity with mild traumatic brain injury symptoms, inflammatory profile, quality of life and functional outcomes: a TRACK-TBI Study

OBJECTIVES

Obesity is associated with chronic inflammation, which may impact recovery from mild traumatic brain injury (mTBI). The objective was to assess the role of obesity in recovery of symptoms, functional outcome and inflammatory blood biomarkers after mTBI.

METHODS

TRACK-TBI is a prospective study of patients with acute mTBI (Glasgow Coma Scale=13-15) who were enrolled ≤24 hours of injury at an emergency department of level 1 trauma centres and followed for 12 months. A total of 770 hospitalised patients who were either obese (body mass index (BMI) >30.0) or healthy mass (BMI=18.5-24.9) were enrolled. Blood concentrations of high-sensitivity C reactive protein (hsCRP), interleukin (IL) 6, IL-10, tumour necrosis factor alpha; Rivermead Post-Concussion Symptoms Questionnaire (RPQ), Quality of Life After Brain Injury and Glasgow Outcome Score-Extended reflecting injury-related functional limitations at 6 and 12 months were collected.

RESULTS

After adjusting for age and gender, obese participants had higher concentrations of hsCRP 1 day after injury (mean difference (MD)=0.65; 95% CI: 0.44 to 0.87, p<0.001), at 2 weeks (MD=0.99; 95% CI: 0.74 to 1.25, p<0.001) and at 6 months (MD=1.08; 95% CI: 0.79 to 1.37, p<0.001) compared with healthy mass participants. Obese participants had higher concentrations of IL-6 at 2 weeks (MD=0.37; 95% CI: 0.11 to 0.64, p=0.006) and 6 months (MD=0.42; 95% CI: 0.12 to 0.72, p=0.006). Obese participants had higher RPQ total score at 6 months (MD=2.79; p=0.02) and 12 months (MD=2.37; p=0.049).

CONCLUSIONS

Obesity is associated with higher symptomatology at 6 and 12 months and higher concentrations of blood inflammatory markers throughout recovery following mTBI.

Applying the Sliding Scale Approach to Quantifying Functional Outcomes Up to Two Years After Severe Traumatic Brain Injury

Outcomes after severe traumatic brain injury (TBI) can be represented by a sliding score that compares actual functional recovery to that predicted by illness severity models. This approach has been applied in clinical trials because of its statistical efficiency and interpretability but has not been used to describe change in functional recovery over time. The objective of this study was to use a sliding scoring system to describe the magnitude of change in Glasgow Outcome Scale Extended (GOSE) score at 6, 12, and 24 months after severe TBI and to compare patients who improved after 6 months to those who did not. This study included consecutive severe TBI patients (Glasgow Coma Scale ≤8; n = 482) from a single center. We grouped patients into four strata based on probability of unfavorable outcome (GOSE = 1-4) using the International Mission on Prognosis and Analysis of Clinical Trials (IMPACT) model, selected a dichotomous GOSE threshold within each stratum, and compared each patient's GOSE to this threshold to calculate a score (GOSE-Sliding Scale [SS]) from -5 to +4 at 6, 12, and 24 months. We compared GOSE-SS at 6 months with GOSE-SS at 12 and 24 months and also compared characteristics of participants who improved after 6 months with characteristics of those who did not using χ2 and t tests. Compared with at 6 months, 40% of patients (n = 74) had improved GOSE-SS at 12 months, and 53% had improved GOSE-SS by 24 months (n = 72). Among those who improved at 12 months, the average magnitude of improvement was 1.7 ± 0.9 and among those who improved at 24 months, the average magnitude of improvement was 1.9 ± 1.0. Those who improved their GOSE-SS score from 6 to 24 months had longer hospital stays (mean-difference = 8.6 days; p = 0.03), longer intensive care unit (ICU) stays (mean-difference = 5.5 days; p = 0.02), and longer ventilator time (mean-difference = 5 days; p = 0.02) than those who worsened. These results support an optimistic long-term outlook for severe TBI patients and emphasize the importance of long-term follow-up in severe TBI survivors.

Interaction of Medical Conditions and Football Exposures Associated with Premortem Chronic Traumatic Encephalopathy Diagnosis in Former Professional American Football Players

BACKGROUND AND OBJECTIVE

Despite being a postmortem diagnosis, former professional American-style football players report receiving chronic traumatic encephalopathy (CTE) diagnoses from medical care providers. However, many players also report other health conditions that manifest with cognitive and psychological symptoms. The purpose of this study was to identify how medical conditions, psychological disorders, and football exposure combinations are associated with former athletes reporting a premortem CTE diagnosis.

METHODS

This study was a cross-sectional cohort survey from 2015 to 2019 of 4033 former professional American-style football players. Demographics (age, race, domestic status, primary care recipient), football-related factors (position, years of professional play, burden of symptoms following head impacts, performance-enhancing drug use), and comorbidities (sleep apnea, psychological disorder status [depression and anxiety; either depression or anxiety; neither depression nor anxiety], diabetes mellitus, attention-deficit/hyperactivity disorder, hypertension, heart conditions, high cholesterol, stroke, cancer, low testosterone, chronic pain, current and maximum body mass index) were recorded. A Chi-square automatic interaction detection (CHAID) decision tree model identified interactive effects between demographics, health conditions, and football exposures on the CTE diagnosis.

RESULTS

Depression showed the strongest univariate association with premortem CTE diagnoses (odds ratio [OR] = 9.5, 95% confidence interval [CI] 6.0-15.3). CHAID differentiated participants with premortem CTE diagnoses with 98.2% accuracy and area under the curve = 0.81. Participants reporting both depression and anxiety were more likely to have a CTE diagnosis compared with participants who reported no psychological disorders (OR = 12.2; 95% CI 7.3-21.1) or one psychological disorder (OR = 4.5; 95% CI 1.9-13.0). Sleep apnea was also associated with a CTE diagnosis amongst those with both depression and anxiety (OR = 2.7; 95% CI 1.4-5.2).

CONCLUSIONS

Clinical phenotypes including psychological disorders and sleep apnea were strongly associated with an increased likelihood of having received a pre-mortem CTE diagnosis in former professional football players. Depression, anxiety, and sleep apnea produce cognitive symptoms, are treatable conditions, and should be distinguished from neurodegenerative disease.

Multidomain concussion symptoms in adolescents: A network analysis

Concussion is a heterogeneous injury involving symptoms and impairment that represent multiple domains (e.g., anxiety, cognitive, vestibular). Network analysis, a modeling technique that estimates relationships among symptoms, provides a statistically sound and clinically practical method for evaluating these interrelationships. The purpose of this study was to examine, using network analysis, relationships among clinical assessments and multidomain symptom report within a sample of adolescent patients following a concussion. Participants included 326 patients (49.7% female) aged 10-21 years presenting to a concussion specialty clinic within 28 days of a diagnosed concussion. Participants completed the Post-Concussion Symptom Scale (PCSS) and Vestibular-Ocular Motor Screening (VOMS) tool at initial visit. Network models were applied to PCSS symptoms initially, and then applied to VOMS and PCSS symptom data together. Dizziness (Expected influence (EI) = 1.10) and sadness (EI = 1.91) were most central (i.e., highest cumulative partial correlations) to the symptom network. Numerous interdomain relationships were supported, including irritability with mental fogginess (edgeweight = 0.12), dizziness with headache (edgeweight = 0.16), and dizziness with vision problems (edgeweight = 0.13). Community analyses resulted in VOMS groupings by domain (e.g., vestibular) and symptom (e.g., dizziness). The findings suggest a more direct focus on symptom interrelationships, such as how dizziness contributes to emotional symptoms, may help guide and better target treatments. Also, results suggest grouping VOMS assessment by symptom (e.g., dizziness) and item (e.g., vestibular-ocular reflex) may better reflect underlying impairments reflected by these symptom-item combinations.

Interaction of admission platelet count with current medications and the risk for chronic subdural recurrence

OBJECTIVE

Chronic subdural hematoma (cSDH) has a reported 10%-24% rate of recurrence after surgery, and prognostic models for recurrence have produced equivocal results. The objective of this study was to leverage a data mining algorithm, chi-square automatic interaction detection (CHAID), which can incorporate continuous, nominal, and binary data into a decision tree, to identify the most robust predictors of repeat surgery for cSDH patients.

METHODS

This was a retrospective cohort study of all patients with SDH from two level 1 trauma centers at a single institution. All patients underwent cSDH evacuation performed by 15 neurosurgeons between 2011 and 2020. The primary outcome was the rate of repeat surgery for recurrent cSDH following the initial evacuation. The authors used CHAID to identify relevant predictors of repeat surgery, including age, sex, comorbidities, postsurgical complications, platelet count prior to the first procedure, midline shift prior to the first procedure, hematoma volume, and preoperative use of anticoagulants, antiplatelets, or statins.

RESULTS

Sixty (13.8%) of 435 study-eligible patients (average age 74.0 years) had a cSDH recurrence. These patients had 2.0 times greater odds of having used anticoagulants. The final CHAID model had an overall accuracy of 87.4% and an area under the curve of 0.76. According to the model, the predictor with the strongest association with cSDH recurrence was admission platelet count. Approximately 26% of patients (n = 23/87) with an admission platelet count < 157 × 109/L had a cSDH recurrence, whereas none of the 44 patients with admission platelets > 313 × 109/L had a recurrence. Approximately 17% of patients in the 157-313 × 109/L platelet group who had used preoperative statins required a second procedure, which was associated with a 2.3 times increased risk for repeat surgery compared to those who had not used statins preoperatively. Among those who had not used preoperative statins, a platelet count ≤ 179 × 109/L on admission for the first procedure was the strongest differentiator for a second surgery (n = 5/22 [23%]), which increased the risk of recurrence by 4.5 times. Among the patients using preoperative statins, the use of anticoagulants was the strongest differentiator for requiring repeat surgery (n = 11/33 [33%]).

CONCLUSIONS

The described model identified platelet count on admission as the most important predictor of repeat cSDH surgery, followed by preoperative statin use and anticoagulant use. Critical cutoffs for platelet count were identified, which future studies should evaluate to determine if they are modifiable or reflective of underlying disease states.

Evaluating Targeted Therapeutic Response With Predictive Blood-Based Biomarkers in Patients With Chronic Mild Traumatic Brain Injury

Chronic consequences of mild traumatic brain injury (mTBI) are heterogeneous, but may be treatable with targeted medical and rehabilitation interventions. A biological signature for the likelihood of response to therapy (i.e., "predictive" biomarkers) would empower personalized medicine post-mTBI. The purpose of this study was to correlate pre-intervention blood biomarker levels and the likelihood of response to targeted interventions for patients with chronic issues attributable to mTBI. Patients with chronic symptoms and/or disorders secondary to mTBI >3 months previous (104 days to 15 years; n = 74) were enrolled. Participants completed pre-intervention assessments of symptom burden, comprehensive clinical evaluation, and blood-based biomarker measurements. Multi-domain targeted interventions for specific symptoms and impairments across a 6-month treatment period were prescribed. Participants completed a follow-up testing after the treatment period. An all-possible model's backward logistic regression was built to identify predictors of improvement in relation to blood biomarker levels before intervention. The minimum clinically important difference (MCID) of the change score (post-intervention subtracted from pre-intervention) for the Post-Concussion Symptom Scale (PCSS) to identify treatment responders from non-responders was the primary outcome. The MCID for total PCSS score was 10. The model to predict change in PCSS score over the 6-month intervention was significant (R² = 0.09; p = 0.01) and identified ubiquitin C-terminal hydrolase L1 (odds ratio [OR] = 2.53; 95% confidence interval [CI], 1.18-5.46; p = 0.02) and hyperphosphorylated tau (p-tau; OR = 0.70; 95% CI, 0.51-0.96; p = 0.03) as significant predictors of symptom improvement beyond the PCSS MCID. In this cohort of chronic TBI subjects, blood biomarkers before rehabilitation intervention predicted the likelihood of response to targeted therapy for chronic disorders post-TBI.

Incidence of Concussion and Associated Risk Factors in Collegiate Soccer: Findings from the NCAA-DoD CARE Consortium

This retrospective cohort study aims to examine concussion incidence rates (IR) in collegiate soccer players and compare IRs based on risk factors including sex, competition level, games/practices, history of concussion, and playing position. Collegiate soccer players were recruited (n = 2,471) from 23 institutions from the NCAA-DoD Concussion Assessment, Research, and Education (CARE) Consortium. Incidence rates for concussion per 1000 athlete exposures (AEs) were calculated across the 2015-16/2016-17 seasons. Incidence rates (IR) comparing risk factor groups were also calculated. A total 162 concussions occurred during the study, for an IR of 0.08/1000 AEs. Females were more likely to have a concussion than males overall (IR = 1.47), and were more likely to have a concussion in games (IR = 1.42) and practices (IR = 2.91). Concussions were more likely during competition compared to practice (IR = 2.53), and less likely in Division III, compared to Divisions I and II, χ² = 6.5, p > .05. In the concussed group, male sex was associated with 2.47 times higher odds of playing defender and 2.29 times higher odds of a collision mechanism. Results confirm previous findings that females and game exposures have higher concussion IR than males and practice exposures. Findings also supported sex differences in IRs based on exposure type, position, and mechanism.

Comparison of machine learning models to predict long-term outcomes after severe traumatic brain injury

OBJECTIVE

An estimated 1.5 million people die every year worldwide from traumatic brain injury (TBI). Physicians are relatively poor at predicting long-term outcomes early in patients with severe TBI. Machine learning (ML) has shown promise at improving prediction models across a variety of neurological diseases. The authors sought to explore the following: 1) how various ML models performed compared to standard logistic regression techniques, and 2) if properly calibrated ML models could accurately predict outcomes up to 2 years posttrauma.

METHODS

A secondary analysis of a prospectively collected database of patients with severe TBI treated at a single level 1 trauma center between November 2002 and December 2018 was performed. Neurological outcomes were assessed at 3, 6, 12, and 24 months postinjury with the Glasgow Outcome Scale. The authors used ML models including support vector machine, neural network, decision tree, and naïve Bayes models to predict outcome across all 4 time points by using clinical information available on admission, and they compared performance to a logistic regression model. The authors attempted to predict unfavorable versus favorable outcomes (Glasgow Outcome Scale scores of 1-3 vs 4-5), as well as mortality. Models' performance was evaluated using the area under the receiver operating characteristic (ROC) curve (AUC) with 95% confidence interval and balanced accuracy.

RESULTS

Of the 599 patients in the database, the authors included 501, 537, 469, and 395 at 3, 6, 12, and 24 months posttrauma. Across all time points, the AUCs ranged from 0.71 to 0.85 for mortality and from 0.62 to 0.82 for unfavorable outcomes with various modeling strategies. Decision tree models performed worse than all other modeling approaches for multiple time points regarding both unfavorable outcomes and mortality. There were no statistically significant differences between any other models. After proper calibration, the models had little variation (0.02-0.05) across various time points.

CONCLUSIONS

The ML models tested herein performed with equivalent success compared with logistic regression techniques for prognostication in TBI. The TBI prognostication models could predict outcomes beyond 6 months, out to 2 years postinjury.

Pilot Biomarker Analysis and Decision Tree Algorithm Modeling of Patients with Chronic Subdural Hematomas

The elderly population are at high risk for developing chronic subdural hematoma (cSDH). Surgical evacuation of cSDH is one of the most common procedures performed in neurosurgery. The present study aims to identify potential inflammatory biomarkers associated with its development and recurrence. Patients (>65 years of age) who presented with symptomatic cSDH (≥1 cm thickness or ≥5 mm midline shift [MLS]), requiring surgical intervention, were prospectively enrolled. The collected cSDH fluid was analyzed for inflammatory markers. Computed tomography (CT) scan data included pre-operative cSDH thickness and MLS. Outcome data included Glasgow Outcome Scale-Extended (GOS-E) score at 3, 6, and 12 months post-surgery, as well as cSDH recurrence. A decision tree model was used to determine the predictive power of extracted analytes for MLS, cSDH thickness, and recurrence. This pilot study includes 20 enrolled patients (mean age 77.9 ± 7.4 years and 85% falls). Rate of cSDH recurrence was 42%, with 21% requiring reoperation. Chemokine (C-X-C motif) ligand 9 (CXCL9) concentrations correlated with cSDH thickness (r = 0.975, p = 0.040). Interleukin (IL)-6 and vascular endothelial growth factor (VEGF)-A concentrations correlated with MLS (r = 0.974, p = 0.005; r = 0.472, p = 0.036, respectively). IL-5 concentrations correlated with more favorable GOS-E scores at 3, 6, and 12 months (r = 0.639, p = 0.006; r = 0.727, p = 0.003; r = 0.693, p = 0.026, respectively). Regulated on activation, normal T-cell expressed and secreted (RANTES) concentrations correlated with complete cSDH resolution (r = 0.514, p = 0.021). The decision tree model identified that higher concentrations of CXCL9 were predictive of MLS (risk ratio [RR] = 12.0), higher concentrations of IL-5 were predictive of cSDH thickness (RR = 4.5), and lower concentrations of RANTES were predictive of cSDH recurrence (RR = 2.2). CXCL9, IL-6, VEGF, IL-5, and RANTES are associated with recurrence after surgery and may be potential biomarkers for predicting cSDH recurrence and neurological outcomes.

Military tactical adaptive decision making during simulated military operational stress is influenced by personality, resilience, aerobic fitness, and neurocognitive function

Laboratory-based studies designed to mimic combat or military field training have consistently demonstrated deleterious effects on warfighter's physical, cognitive, and emotional performance during simulated military operational stress (SMOS).

Purpose

The present investigation sought to determine the impact of a 48-h simulated military operational stress (SMOS) on military tactical adaptive decision making, and the influence of select psychological, physical performance, cognitive, and physiological outcome measures on decision making performance.

Methods

Male (n = 48, 26.2 ± 5.5 years, 177.7 ± 6.6 cm, 84.7 ± 14.1 kg.) subjects currently serving in the U.S. military were eligible to participate in this study. Eligible subjects completed a 96-h protocol that occurred over five consecutive days and four nights. Day 2 (D2) and day 3 (D3) consisted of 48-h of SMOS wherein sleep opportunity and caloric needs were reduced to 50%. Differences in SPEAR total block score from baseline to peak stress (D3 minus D1) were calculated to assess change in military tactical adaptive decision making and groups were stratified based on increase (high adaptors) or decrease (low adaptors) of the SPEAR change score.

Results

Overall, military tactical decision-making declined 1.7% from D1 to D3 (p < 0.001). High adaptors reported significantly higher scores of aerobic capacity (p < 0.001), self-report resilience (p = 0.020), extroversion (p < 0.001), and conscientiousness (p < 0.001). at baseline compared to low adaptors, while low adaptors reported greater scores in Neuroticism (p < 0.001).

Conclusion

The present findings suggest that service members whose adaptive decision making abilities improved throughout SMOS (i.e., high adaptors) demonstrated better baseline psychological/self-reported resilience and aerobic capacity. Further, changes in adaptive decision-making were distinct from those of lower order cognitive functions throughout SMOS exposure. With the transition of future military conflicts placing higher priority on enhancing and sustaining cognitive readiness and resiliency, data presented here demonstrates the importance of measuring and categorizing baseline measures inherent to military personnel, in order to change and train one's ability to suffer less of a decline during high stress conditions.

Less daytime sleepiness and slow wave activity during sleep predict better physical readiness in military personnel

BACKGROUND

Military personnel must maintain physical performance despite exposure to operational stressors such as sleep loss, caloric restriction and high cognitive load. Habitual sleep and specific sleep features are positively associated with fitness and may contribute to physical performance in operational settings. Further, by affecting muscle recovery, sleep may contribute to the ability to maintain performance across multiple days of exposure to operational stressors.

OBJECTIVES

We examined the role of individual differences in baseline sleep on baseline physical performance and on change in physical performance throughout exposure to simulated military operational stress (SMOS).

METHODS

Military personnel (36 male, 9 female, 26.3 ± 5.3 years) completed a 5-day SMOS protocol during which they completed a tactical mobility test daily. Sleep questionnaires were administered at intake and sleep was monitored each night with polysomnography. Lasso regressions were used to identify meaningful predictors of physical performance at baseline and of change in physical performance across SMOS.

RESULTS

Better aerobic fitness, lower daytime sleepiness (Epworth Sleepiness Scale), and lower absolute slow wave activity (0.5-4 Hz) predicted better physical performance at baseline (66.1% of variance explained), but did not relate to changes in performance.

CONCLUSIONS

Collectively, higher daytime sleepiness and slow wave activity may reflect more chronic exposure to insufficient sleep and higher baseline sleep drive, which in turn led to compromised physical performance. The findings suggest that low self-report sleepiness and low objective slow wave activity may reflect two quantifiable markers of healthy sleep behaviors that have implications for operational performance.

Association of Plasma Biomarkers with Sleep Outcomes and Treatment Response After Mild Traumatic Brain Injury

Sleep disturbances occur in up to 70% of patients with mild traumatic brain injury (mTBI). Modern mTBI management recommends targeted treatment for the patient's unique clinical manifestations (i.e., obstructive sleep apnea, insomnia). The purpose of this study was to evaluate the association of plasma biomarkers with symptom reports, overnight sleep evaluations, and response to treatment for sleep disturbances secondary to mTBI. This study is a secondary analysis of a prospective multiple interventional trial of patients with chronic issues related to mTBI. Pre- and post-intervention assessments were conducted, including overnight sleep apnea evaluation, the Pittsburgh Sleep Quality Index (PSQI), and blinded analysis of blood biomarkers. Bivariate Spearman correlations were conducted for pre-intervention plasma biomarker concentrations and 1) PSQI change scores and 2) pre-intervention sleep apnea outcomes (i.e., oxygen saturation measures). A backward logistic regression model was built to evaluate the association of pre-intervention plasma biomarkers with improvement in PSQI over the treatment period (p < 0.05). Participants were 36.3 ± 8.6 years old and 6.1 ± 3.8 years from their index mTBI. Participants reported subjective improvements (PSQI = -3.7 ± 3.8), whereas 39.3% (n = 11) had improved PSQI scores beyond the minimum clinically important difference (MCID). PSQI change scores correlated with von Willebrand factor (vWF; ρ = -0.50; p = 0.02) and tau (ρ = -0.53; p = 0.01). Hyperphosphorylated tau correlated with average saturation (ρ = -0.29; p = 0.03), lowest desaturation (ρ = -0.27; p = 0.048), and baseline saturation (ρ = -0.31; p = 0.02). The multi-variate model (R ² = 0.33; p = 0.001) retained only pre-intervention vWF as a predictor (odds ratio = 3.41; 95% confidence interval, 1.44-8.08; p = 0.005) of improving PSQI scores beyond the MCID. vWF had good discrimination (area under the curve = 0.83; p = 0.01), with an overall accuracy of 77%, sensitivity of 46.2%, and specificity of 90.0%. Validation of vWF as a potential predictive biomarker of sleep improvement post-mTBI could optimize personalized management and healthcare utilization.

Sex Differences on the Concussion Clinical Profiles Screening in Adolescents With Sport-Related Concussion

CONTEXT

Sex differences influence symptom presentations after sport-related concussion and may be a risk factor for certain concussion clinical profiles.

OBJECTIVE

To examine sex differences on the Concussion Clinical Profile Screen (CP Screen) in adolescents after sport-related concussion.

DESIGN

Cross-sectional study.

SETTING

A concussion specialty clinic.

PATIENTS OR OTHER PARTICIPANTS

A total of 276 adolescent (age = 15.02 ± 1.43 years; girls = 152 [55%]) athletes with a recently diagnosed concussion (≤30 days).

MAIN OUTCOME MEASURE(S)

The 5 CP Screen profiles (anxiety mood, cognitive fatigue, migraine, vestibular, ocular) and 2 modifiers (neck, sleep), symptom total, and symptom severity scores were compared using a series of Mann-Whitney U tests between boys and girls.

RESULTS

Girls (n = 152) scored higher than boys (n = 124) on the cognitive fatigue (U = 7160.50, z = -3.46, P = .001) and anxiety mood (U = 7059, z = -3.62, P < .001) factors but not on the migraine (U = 7768, z = -2.52, P = .01) factor. Girls also endorsed a greater number of symptoms (n = 124; U = 27233, z = -3.33, P = .001) and scored higher in symptom severity (U = 7049, z = -3.60, P < .001) than boys.

CONCLUSIONS

Among adolescents, symptom endorsement on the CP Screen varied based on sex, and clinicians need to be aware of these differences, especially when evaluating postconcussion presentation in the absence of baseline data.

Prognostic Models for Traumatic Brain Injury Have Good Discrimination but Poor Overall Model Performance for Predicting Mortality and Unfavorable Outcomes

BACKGROUND

The most extensively validated prognostic models for traumatic brain injury (TBI) are the Corticoid Randomization after Significant Head Injury (CRASH) and International Mission on Prognosis and Analysis of Clinical Trials (IMPACT). Model characteristics outside of area under the curve (AUC) are rarely reported.

OBJECTIVE

To report the discriminative validity and overall model performance of the CRASH and IMPACT models for prognosticating death at 14 days (CRASH) and 6 months (IMPACT) and unfavorable outcomes at 6 months after TBI.

METHODS

This retrospective cohort study included prospectively collected patients with severe TBI treated at a single level I trauma center (n = 467). CRASH and IMPACT percent risk values for the given outcome were computed. Unfavorable outcome was defined as a Glasgow Outcome Scale-Extended score of 1 to 4 at 6 months. Binary logistic regressions and receiver operating characteristic analyses were used to differentiate patients from the CRASH and IMPACT prognostic models.

RESULTS

All models had low R 2 values (0.17-0.23) with AUC values from 0.77 to 0.81 and overall accuracies ranging from 72.4% to 78.3%. Sensitivity (35.3-50.0) and positive predictive values (66.7-69.2) were poor in the CRASH models, while specificity (52.3-53.1) and negative predictive values (58.1-63.6) were poor in IMPACT models. All models had unacceptable false positive rates (20.8%-33.3%).

CONCLUSION

Our results were consistent with previous literature regarding discriminative validity (AUC = 0.77-0.81). However, accuracy and false positive rates of both the CRASH and IMPACT models were poor.

Performance of CRASH and IMPACT Prognostic Models for Traumatic Brain Injury at 12 and 24 Months Post-Injury

The Corticoid Randomization after Significant Head Injury (CRASH) and International Mission for Prognosis and Analysis of Clinical Trials (IMPACT) prognostic models are the most reported prognostic models for traumatic brain injury (TBI) in the scientific literature. However, these models were developed and validated to predict 6-month unfavorable outcome and mortality, and growing evidence supports continuous improvements in functional outcome after severe TBI up to 2 years post-injury. The purpose of this study was to evaluate CRASH and IMPACT model performance beyond 6 months post-injury to include 12 and 24 months post-injury. Discriminative validity remained consistent over time and comparable to earlier recovery time points (area under the curve = 0.77-0.83). Both models had poor fit for unfavorable outcomes, explaining less than one quarter of the variation in outcomes for severe TBI patients. The CRASH model had significant values for the Hosmer-Lemeshow test at 12 and 24 months, indicating poor model fit past the previous validation point. There is concern in the scientific literature that TBI prognostic models are being used by neurotrauma clinicians to support clinical decision making despite the goal of the models' development being to support research study design. The results of this study indicate that the CRASH and IMPACT models should not be used in routine clinical practice because of poor model fit that worsens over time and the large, unexplained variance in outcomes.

Telling the Whole Story: Bibliometric Network Analysis to Evaluate Impact of Media Attention on Chronic Traumatic Encephalopathy Research

There is a national debate regarding the existence of a relationship between contact sport participation and future risk of neurodegenerative disease. We employed bibliometrics and altmetrics to quantify the academic, popular, and social media impact of published scientific articles that report an association between contact sports or military service with chronic traumatic encephalopathy (CTE+), and compare with those scientific articles that report null or no association of contact sports or military service with CTE (CTE-). In this cross-sectional study, we extracted number of citations, total link strength, altmetric score, number of news stories, media outlets, and Twitter interaction from published CTE articles. The top 10 most cited articles were statistically compared on these outcomes using Mann-Whitney U tests. CTE+ publications had an average of 101 citations per article, Altmetric score of 272, 36 news stories in 26 media outlets, and upper-bound of Twitter users of 402,159. CTE- publications had an average of 29 citations per article, Altmetric score of 39, two news stories and media outlets, and upper-bound of Twitter users of 91,070. Top 10 CTE+ publications had, on average, 94% more citations (p < 0.001), 95% higher altmetric scores (p = 0.01), 99% higher number of news stories (p = 0.01), 98% higher number of media outlets (p = 0.01), and reached 95% more Twitter users than top 10 CTE- publications (p = 0.11). The bibliometric analysis indicates a significant inequality in media dissemination and popular consumption of scientific findings that do not support a relationship between contact sports or military service and future neurodegeneration.

Optimizing VOMS for identifying acute concussion in collegiate athletes: Findings from the NCAA-DoD CARE consortium

The Vestibular/Ocular-Motor Screening (VOMS), an important component in acute (<72 h) sport-related concussion (SRC) assessment, is increasingly used alongside the Sport Concussion Assessment Tool (SCAT) and as part of the Military Acute Concussion Evaluation 2 (MACE2). VOMS demonstrates clinically useful diagnostic accuracy for acute SRC and improves the overall utility when added to the SCAT3. However, potential overlap among VOMS's vestibular and oculomotor items suggests the possibility of a more efficient version. VOMS and SCAT3 scores were analyzed for 3,958 preseason (47.8% female) and 496 acute-SRC (37.5% female) NCAA-DoD Concussion Assessment, Research, and Education (CARE) consortium collegiate athlete evaluations. Analyses revealed very large effect sizes (d = 2.39-2.45) and high correlations (rho = 0.95-0.99) among all VOMS items except near point of convergence distance (d = 0.79, rho ≤ 0.341). Receiver operating characteristic (ROC) curve analyses showed clinically useful discriminative utility for VOMS Total (AUC = 0.85) and the VOMS Total change score, where pretest symptoms were incorporated (AUC = 0.81). A modified VOMS (mVOMS) consisting of four items (smooth pursuits, horizontal saccades, horizontal vestibulo-ocular reflex, visual motion sensitivity) yielded identical AUCs to VOMS Total. Integer cutoff analyses suggest a score of ≥4 for VOMS Total and ≥4 for mVOMS Total optimizes concussion identification. Incorporating VOMS or mVOMS into SCAT3 (AUC = 0.79) significantly improved the combined tool's acute utility for acute concussion identification by a maximum of 4% (SCAT3+VOMS AUC = 0.84, SCAT3+mVOMS AUC = 0.83). Future versions of SCAT or MACE may want to consider incorporating a more parsimonious VOMS for the purpose of identifying acute concussion.

Combined effects of time-of-day and simulated military operational stress on perception-action coupling performance

Perception-action coupling, the ability to 'read and react' to the environment, is essential for military personnel to operate within complex and unpredictable environments. Exposure to military operational stressors (e.g., caloric restriction, sleep loss, physical exertion), including around-the-clock operations, may compromise perception-action coupling, thereby impacting performance and safety. We examined the combined effects of simulated military operational stress (SMOS) and time-of-day on perception-action coupling. Fifty-seven active duty and reservist military personnel (45 M; 26.4 ± 5.6 years) completed a 5-day SMOS protocol that included two consecutive days of caloric restriction, and sleep restriction, and disruption. Participants completed a tablet-based perception-action coupling task (PACT) that involves perceiving whether virtual balls fit through virtual apertures. Familiarization occurred on day 0. Eight trials across day 1 (18:00, 22:00), 2 (04:00, 18:00, 22:00) and 3 (04:00, 18:00, 22:00) were analyzed. Mixed models were run to examine the interactive and main effects of day, and time-of-day on PACT response speed and accuracy outcomes. PACT response speed and accuracy outcomes improved at 18:00 and 22:00, whereas performance at 04:00 deteriorated across days. Perception-action coupling performance was resilient to SMOS, except in the early morning when the circadian drive for sleep is high, and the effects of sleep loss are more prominent.

Association of Multidomain Assessment Outcomes with Referral for Vestibular Therapy following Concussion

CONTEXT

Multiple aspects of a multidomain assessment have been validated for identifying concussion, however, researchers have yet to determine which components are related to referral for vestibular therapy.

OBJECTIVE

To identify which variables from a multidomain assessment were associated with receiving a referral for vestibular therapy following a concussion.

DESIGN

Retrospective chart review, level of evidence 3.

PATIENTS OR OTHER PARTICIPANTS

Participants (n=331; age: 16.9±7.2; 39.3% female) were diagnosed with a concussion per international consensus criteria by a clinical neuropsychologist after presenting to a concussion specialty clinic.

MAIN OUTCOME MEASURES

Medical chart data was extracted from the first clinical visit regarding pre-injury medical history, computerized neurocognition, Post-Concussion Symptom Scale (PCSS), Concussion Clinical Profiles Screen (CP-Screen) and Vestibular Ocular Motor Screening (VOMS) within 16.2±46.7 days of injury. Five backwards logistic regression models were built to associate the outcomes from each of the five included assessments with referral for vestibular therapy. A final logistic regression model was built using variables retained in the previous five models as potential predictors of referral for vestibular therapy.

RESULTS

The five models built from individual components of the multidomain assessment predicted referral for vestibular therapy (R2= 0.01-0.28) with 1 to 6 statistically significant variables. The final multivariate model (R2= 0.40) retained 9 significant variables, represented by each of the five multidomain assessments except neurocognition. Variables with the strongest association to vestibular therapy referral were motor vehicle accident mechanism of injury (odds ratio [OR]=15.45), migraine history (OR=3.25), increased headache when concentrating (OR=1.81) and horizontal vestibular ocular reflex (OR=1.63).

CONCLUSIONS

The present study demonstrates the utility of a multidomain assessment, and identifies outcomes associated with a referral for vestibular therapy following a concussion.

The Role of Age, Sex, Body Mass Index, and Sport Type on the Dynamic Exertion Test in Healthy Athletes: A Cross-Sectional Study

BACKGROUND

The dynamic exertion test (EXiT) was developed to help inform return to play after sport-related concussion, but some factors may threaten the internal validity of EXiT and affect clinical interpretation.

OBJECTIVE

To compare age, sex, BMI, and sport types across EXiT physiological [pre-EXiT and post-EXiT percentage of maximum heart rate (HR %max) and blood pressure (BP)], performance (change-of-direction task completion time and committed errors), and clinical [symptoms and rating of perceived exertion (RPE)] outcomes among healthy adolescents and adults.

STUDY DESIGN

Cross-sectional.

METHODS

Eighty-seven participants ( F = 55, 37.4%) reported symptoms and RPE during the EXiT, which consists of a 12-minute treadmill running protocol, and the dynamic circuit, ball toss, box shuffle (SHUF) and carioca (CAR), zig zag (ZZ), proagility (PA), and arrow agility (AA) tasks. Independent samples t tests were conducted for pre-EXiT and post-EXiT HR %max and BP and change-of-direction task completion time and Mann-Whitney U tests for errors, symptoms, and RPE. A series of 1-way analysis of variance (ANOVAs) and Kruskal-Wallis H tests were conducted to compare collision, contact, and noncontact sport types.

RESULTS

Adolescents had lower completion time across AA ( P = 0.01) and male athletes lower than female athletes on CAR, ZZ, PA, and AA ( P < 0.04). Male athletes reported greater RPE after the SHUF, CAR, and AA ( P < 0.03). HR %max , errors, and symptoms were equivocal across all subgroups ( P > 0.05).

CONCLUSION

Age and sex should be considered in the interpretation of performance and clinical, but not physiological, EXiT outcomes. The EXiT is a standardized exercise assessment and generalizable to healthy athletes.

A-01 Changes in Fixational Eye Movements (FEMs) Following Concussion

Purpose: Identify changes in fixational eye movement (FEMs) outcomes following concussion and assess the association of FEMs outcomes with clinical outcomes including symptoms, neurocognitive, and vestibular/ocular motor. Methods: Participants included thirty-three individuals (13–27 years old; 54.5% female) diagnosed with concussion within the past 21 days. Concussion diagnosis was determined using current consensus guidelines. A tracking scanning laser ophthalmoscope (TSLO) was used to measure FEMS. Participants completed ImPACT, PCSS, and VOMS. Within-subjects changes in FEMS outcomes were calculated using paired-samples t-tests. A backwards stepwise linear regression to predict days to clearance was utilized with all FEMS outcomes as predictors. Results: MeanDriftH (slope of cumulative drift regression calculated horizontally; mean difference = 0.04; p = 0.03; Cohen’s d = 0.43) and drift proportion significantly changed over time (mean difference = 0.03; p = 0.03, d = 0.44). Average peak velocity of microsaccade (MsPkVel) predicted days to recovery (R = 0.26; p = 0.045; n = 24). MsPkVel and average duration of blink correlated with select reports of nausea on VOMS. Microsaccade frequency (r = −0.36; p = 0.04) correlated with NPC fogginess. Drift amplitude (DriftAmp) correlated with NPC distance (r = −0.41; p = 0.02) and VMS headache (r = 0.35; p = 0.04). MeanDriftH was negatively correlated with verbal memory (r = −0.44; p = 0.01), whereas DriftAmp was positively correlated (r = 0.50; p = 0.003). Bivariate contour ellipse area was correlated (r = 0.43; p = 0.01) with slower reaction time on ImPACT. Conclusions: FEMs outcomes demonstrated significant change and were useful in predicting recovery time following concussion. FEMs measurements may provide brief, objective data to augment current clinical assessment and inform prognosis for recovery. Future researchers should examine FEMS outcomes from pre- to post-concussion and explore age and sex differences.

Characteristics of concussion subtypes from a multidomain assessment

OBJECTIVE

The aim of this study was to analyze the best combination of clinical variables associated with concussion subtypes using a multidomain assessment comprising medical history; symptoms; and cognitive, ocular, and vestibular impairment in a cohort of patients presenting to a concussion specialty clinic.

METHODS

Adolescent patients (n = 293) completed demographics and medical history, Concussion Clinical Profiles Screening, Immediate Post-Concussion Assessment and Cognitive Testing, and vestibular ocular motor screening at their first visit (mean 7.6 ± 7.8 days postinjury) to a concussion specialty clinic. Each participant was adjudicated to have one or more subtype (anxiety/mood, cognitive, migraine, ocular, and vestibular) by a healthcare professional based on previously published criteria. A series of backward, stepwise logistic regressions were used to identify significant predictors of concussion subtypes, and predictive probabilities from the logistic regression models were entered into area under the receiver operating characteristic curve (AUC) models.

RESULTS

Each of 5 logistic regression models predicting primary subtypes accounted for 28%-50% of the variance (R2 = 0.28-0.50, p < 0.001) and included 2-8 significant predictors per model. Each of the models significantly differentiated the primary subtype from all other subtypes (AUC = 0.76-0.94, p < 0.001).

CONCLUSIONS

These findings suggest that each concussion subtype can be identified using specific outcomes from a multidomain assessment. Clinicians can employ such an approach to better identify and monitor recovery from subtypes as well as guide interventions.

Exploration of Race and Ethnicity, Sex, Sport-Related Concussion, Depression History, and Suicide Attempts in US Youth

IMPORTANCE

Racial, ethnic, and sex disparities for concussion incidence and suicide attempts in youth have been reported, but data on the interaction of these variables in a large national data set are lacking. Understanding how race and ethnicity interact with sex and concussion to influence suicide attempts could yield critical information on the sociocultural impact of brain injury and mental health in US youth.

OBJECTIVE

To examine the associations of concussion history, race and ethnicity, and sex with reported suicide attempts among adolescents.

DESIGN, SETTING, AND PARTICIPANTS

This population-based cross-sectional cohort study used data from US Youth Risk Behavior Surveillance System (YRBSS) survey respondents between 2017 and 2019. Data were analyzed from May 2021 to January 2022.

EXPOSURES

Respondents reported sport- or recreation-related concussion (yes or no), depression (yes or no), and suicide attempt (yes or no) over the previous 12 months, along with race and ethnicity (categorized as American Indian or Alaska Native, Asian, Black, Hispanic/Latino, multiracial, Native Hawaiian or other Pacific Islander, and White), and sex (male or female).

MAIN OUTCOMES AND MEASURES

Two Chi-Square Automatic Interaction Detection (CHAID) decision tree models were built. The first was suicide attempt with depression history (SA-DEP), the second was suicide attempt without depression history (SA-NO DEP). CHAID uses risk factors (eg, number of concussions, race and ethnicity, sex) to divide the study sample into a series of subgroups that are nested within each other. Risk ratios (RRs) and 95% CIs were calculated for each subgroup to provide effect estimates.

RESULTS

A total of 28 442 youths aged up to 18 years (mean [SD] age, 14.6 [3.0] years; 14 411 [50.7%] female) responded to the survey. The CHAID decision trees revealed a complex interaction between race, sex, and concussion history for attempting suicide, which differed by depression history (overall accuracy, 84.4%-97.9%). Overall, depression history was the variable most strongly associated with SA (adjusted odds ratio, 11.24; 95% CI, 10.27-12.29). Concussion was the variable most strongly associated with SA-DEP (RR, 1.31; 95% CI, 1.20-1.51; P < .001). Black, Hispanic/Latino, or multiracial race and ethnicity were associated with increased risk for SA-DEP compared with others (RR, 1.59; 95% CI, 1.38-1.84; P < .001). American Indian or Alaska Native, Black, and Hispanic/Latino race and ethnicity were associated with increased risk for SA-NO DEP (RR, 1.89; 95% CI, 1.54-2.32; P < .001) compared with the remaining population.

CONCLUSIONS AND RELEVANCE

These findings suggest that clinicians should consider race, ethnicity, and sex when evaluating the role of sport- or recreation-related concussion on suicide risk among US youth.

Test-Retest, Interrater Reliability, and Minimal Detectable Change of the Dynamic Exertion Test (EXiT) for Concussion

BACKGROUND

The Dynamic Exertion Test (EXiT) was developed to inform return-to-play (RTP) decision-making following clinical recovery from sport-related concussion (SRC). The purpose of the current study was to document intrarater and test-retest reliability and minimal detectable change (MDC) scores for physiological [heart rate (HR) and blood pressure], performance (change-of-direction task completion time and errors), and clinical outcomes (endorsed symptoms, perceived exertion) of EXiT, and interrater reliability of performance outcomes.

HYPOTHESIS

Healthy athletes would exhibit stable physiological responses to the EXiT across visits, demonstrate consistent change-of-direction task completion time between consecutive trials at each visit, and the fastest time (of 2 trials) across visits, and endorse equivocal symptoms and effort across visits.

STUDY DESIGN

Cross-sectional, test-retest.

LEVEL OF EVIDENCE

Level 3.

METHODS

Seventy-nine (female: 34 [43%], 19.6 ± 5.0 years) athletes completed the EXiT at 2 study visits (8.7 ± 4.7 days between visits). Two-way, mixed, intraclass correlation coefficients (ICCs) were used to evaluate intrarater and test-retest reliability. Cronbach's alpha was used to document the internal consistency of symptoms at each visit, and MDC scores were calculated on the physiological, performance, and clinical outcomes.

RESULTS

Measured and percentage of age-estimated maximum HR were reliable following EXiT (ICC = 0.579-0.618). Change-of-direction task completion time (MDC range = 0.75-8.70 s) had good-to-excellent test-retest (ICC = 0.703-0.948) and interrater (ICC = 0.932-0.965) reliability. Symptoms had a high internal consistency at visits 1 (α = 0.894) and 2 (α = 0.805) and were reliable across visits (ICC = 0.588).

CONCLUSION

The current investigation established test-retest reliability in addition to MDC scores of an objective dynamic exercise assessment among healthy adolescent and adult athletes. The EXiT may be an objective approach to inform RTP decision-making following SRC recovery.

CLINICAL RELEVANCE

The EXiT is a clinically feasible exertion-based assessment that can be readily administered in a variety of outpatient clinical settings.

Temporal Differences in Concussion Symptom Factors in Adolescents following Sports-Related Concussion

OBJECTIVE

To evaluate temporal differences in concussion symptoms up to 30 days following a sports-related concussion.

STUDY DESIGN

Adolescent and young adult athletes (n = 782) were separated based on time since injury at presentation as Early (0-7 days; n = 321, age: 15.4 ± 1.9 years, 51.7% female), Middle (8-14 days; n = 281, age: 15.8 ± 2.2 years, 54.8% female), and Late (15-30 days; n = 180, age: 15.6 ± 1.8 years, 52.8% female). All participants completed the 22-item Post-Concussion Symptom Scale at first visit. A confirmatory factor analysis was completed separately for each time since injury cohort using a 4-component model reported previously.

RESULTS

The confirmatory factor analysis model fit was acceptable for Early, Middle, and Late (using cognitive-migraine-fatigue, affective, sleep, and somatic factors). Both affective (change = 0.30; P = .01; Cohen d = 0.30) and sleep (change = 0.51; P ≤ .001; Cohen d = 0.47) factors were significantly greater in the Late group compared with the Early, but not Middle, groups. The previously reported 4-factor symptom model, including cognitive-migraine-fatigue, affective, somatic, and sleep factors, was appropriate for adolescents up to 30 days' postinjury. However, adolescents who presented between 15 and 30 days' postinjury reported greater affective and sleep symptoms than those who presented within 1 week.

CONCLUSIONS

Clinicians should consider these temporal differences when evaluating concussion symptoms in adolescents, as greater affective and sleep symptoms can be predictive of prolonged recovery/persistent complications.

Utility of VOMS, SCAT3, and ImPACT Baseline Evaluations for Acute Concussion Identification in Collegiate Athletes: Findings From the NCAA-DoD Concussion Assessment, Research and Education (CARE) Consortium

BACKGROUND

The Vestibular/Ocular-Motor Screening (VOMS) is a valuable component of acute (<72 hours) sports-related concussion (SRC) assessments and is increasingly used with the Immediate Post-concussion Assessment and Cognitive Testing (ImPACT) instrument and the third edition of the Sport Concussion Assessment Tool (SCAT3). Research has suggested that VOMS acute postinjury scores are useful in identifying acute concussion. However, the utility of preseason baseline measurements to improve diagnostic accuracy remains ambiguous. To this end, there is a need to determine how reliable VOMS baseline assessments are across years and whether incorporating individuals' baseline performance improves diagnostic yield for acute concussions.

PURPOSE

To analyze VOMS, SCAT3, and ImPACT to evaluate the test-retest reliability of consecutive-year preseason baseline assessments to directly compare the diagnostic utility of these tools when incorporating baseline assessments versus using postinjury data alone to identify acute SRC.

STUDY DESIGN

Cohort study (diagnosis); Level of evidence, 2.

METHODS

Preseason and postinjury VOMS, SCAT3, ImPACT Post-Concussion Symptom Scale (PCSS), and ImPACT composite scores were analyzed for 3958 preseason (47.7% female) and 496 acute (≤48 hours) SRC (37.5% female) collegiate athlete evaluations in the National Collegiate Athletic Association-Department of Defense Concussion Assessment Research and Education Consortium. Descriptive statistics, Kolmogorov-Smirnov significance, and Cohen d effect size were calculated. Consecutive-year baseline reliability was evaluated for a subset of 447 athlete encounters using Pearson r, Cohen κ, Cohen d, and 2-way mixed intraclass correlation coefficients (ICCs). Wilcoxon signed rank tests were used to determine the statistical significance between population performances, and the 90% reliable change index (RCI) was calculated from the test-retest results. Preseason to postinjury change scores were then calculated from each tool's RCI. Finally, receiver operating characteristic (ROC) curve analyses were conducted, and DeLong method was used to compare the area under the curve (AUC) of raw postinjury scores versus change scores from preseason baseline assessments. Potential effects of sex, medical history (learning disorders or attention-deficit/hyperactivity disorder), and outlier data were also explored.

RESULTS

Effect sizes were large, and overall predictive utilities were clinically useful for postinjury VOMS Total (d = 2.44; AUC = 0.85), the SCAT3 Symptom Evaluation total severity score (d = 1.74; AUC = 0.82), and the ImPACT PCSS total severity score (d = 1.67; AUC = 0.80). Comparatively, effect sizes were small and predictive utilities were poor for Standardized Assessment of Concussion (SAC), modified Balance Error Scoring System (mBESS), and all ImPACT composites (d = 0.11-0.46; AUC = 0.48-0.59). Preseason baseline test-retest reliability was poor to moderate (r = 0.23-0.52; κ = 0.32-0.36; ICC = 0.36-0.68) for all assessments except ImPACT Visual Motion Sensitivity (r = 0.73; ICC = 0.85). Incorporating baseline scores for VOMS Total, SCAT3 (Symptom Evaluation, SAC, mBESS), ImPACT PCSS, or ImPACT composites did not significantly improve AUCs.

CONCLUSION

VOMS Total and symptom severity (SCAT3, PCSS) total scores had large effect sizes and clinically useful AUCs for identifying acute concussion. However, all tools demonstrated high within-patient test-retest variability, resulting in poor reliability. The findings in this sample of collegiate athletes suggest that incorporating baseline assessments does not significantly increase diagnostic yield for acute concussion.

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.

Fixational eye movements following concussion

The purpose of this study was to evaluate fixational eye movements (FEMs) with high spatial and temporal resolution following concussion, where oculomotor symptoms and impairments are common. Concussion diagnosis was determined using current consensus guidelines. A retinal eye-tracking device, the tracking scanning laser ophthalmoscope (TSLO), was used to measure FEMs in adolescents and young adults following a concussion and in an unaffected control population. FEMs were quantified in two fixational paradigms: (1) when fixating on the center, or (2) when fixating on the corner of the TSLO imaging raster. Fixational saccade amplitude in recent concussion patients (≤ 21 days) was significantly greater, on average, in the concussion group (mean = 1.03°; SD = 0.36°) compared with the controls (mean = 0.82°; SD = 0.31°), when fixating on the center of the imaging raster (t = 2.87, df = 82, p = 0.005). These fixational saccades followed the main sequence and therefore also had greater peak velocity (t = 2.86, df = 82, p = 0.006) and peak acceleration (t = 2.80, df = 82, p = 0.006). These metrics significantly differentiated concussed from controls (AUC = 0.67-0.68, minimum p = 0.005). No group differences were seen for the drift metrics in either task or for any of the FEMs metrics in the corner-of-raster fixation task. Fixational saccade amplitudes were significantly different in the concussion group, but only when fixating on the center of the raster. This task specificity suggests that task optimization may improve differentiation and warrants further study. FEMs measured in the acute-to-subacute period of concussion recovery may provide a quick (<3 minutes), objective, sensitive, and accurate ocular dysfunction assessment. Future work should assess the impact of age, mechanism of injury, and post-concussion recovery on FEM alterations following concussion.

Association of impulsivity, physical development, and mental health to perceptual-motor control after concussion in adolescents

HIGHLIGHTS

After SRC, adolescents had deficits in action boundary perception accuracy, while reporting higher depression symptoms and impulsivity, including attention and cognitive instability components.Certain domains of impulsivity were predictive of action boundary perception accuracy and each perception actualization measure in the concussed group.ADD/ADHD history, anxiety scores, and physical development ratings were also significant predictors of perceptual-motor accuracy and actualization time.

Effects of the COVID-19 Pandemic on Patients with Concussion Presenting to a Specialty Clinic

The purpose of this study is to examine the effects of the COVID-19 pandemic on patients presenting with concussion at a specialty clinic. This study used a retrospective cohort design to compare participants (n = 3021) with a suspected concussion, including a Pandemic cohort (n = 1139; March 2020-February 2021) and a Pre-Pandemic cohort (n = 1882; March 2019-February 2020). Concussions and patient characteristics including age, sex, days since injury, and injury mechanism were extracted from an electronic health record. There were 39.5% (n = 743) fewer concussions in Pandemic. Pandemic presented to the clinic 25.8 days later (p < 0.001) and were 1.9 years older (p < 0.001) than Pre-Pandemic. Sport-related concussions decreased 59.6% overall for Pandemic. Pandemic was associated with proportional increases of concussions involving recreational activities (odds ratio [OR] = 6.11; p < 0.001), motor vehicle collisions (OR = 1.39; p < 0.001), and falls/assaults (OR = 1.33; p < 0.001). A total of 9.4% (107/1139) of all Pandemic concussion initial clinical visits were performed using telehealth (0% in Pre-Pandemic). Concussion visit volume to a sub-specialty clinic decreased by approximately 40% during the COVID-19 pandemic and patients presented to the clinic nearly 1 month later. The increase in telehealth highlights the potential to expand clinical care outreach during the current and future pandemics or similar restrictive time periods.

Minimum detectable change and false positive rates of the vestibular/ocular motor screening (VOMS) tool: an NCAA-DoD care consortium analysis

OBJECTIVE

To derive minimum detectable change (MDC) across individual Vestibular-Ocular Motor Screening (VOMS) items and VOMS overall score in 17-25 years old collegiate athletes and to examine false positive rates.

METHOD

Participants (n = 378) completed VOMS pre-season for two consecutive years. MDC was identified for individual VOMS symptom items and NPC distance (cm). Both total and change methods of VOMS scoring were included in analysis.

RESULTS

Regarding total scoring, MDC for ocular VOMS symptom items was 1 and MDC for vestibular VOMS symptoms items was 2. MDC for NPC was 4 cm and for VOMS overall score was 10. Regarding change scoring, MDC for each VOMS symptom item was 1, and for VOMS overall score was 8. False positives ranged from 5.3% to 15.9%.

CONCLUSIONS

This study presents MDCs for each VOMS item and overall VOMS score, using total and change scoring. These values can be considered true change outside measurement error with 95% confidence in a 17-25 year old collegiate athlete population.

False Positive Rates and Associated Risk Factors on the VOMS and mBESS in U.S. Military Personnel

CONTEXT

In 2018, the U.S. military developed the Military Acute Concussion Evaluation-2 (MACE-2) to inform acute evaluation of mTBI. However, researchers have yet to investigate false positive rates for components of the MACE-2 including the Vestibular-Ocular Motor Screen (VOMS) and modified Balance Error Scoring System (mBESS) in military personnel.

OBJECTIVE

To examine factors associated with false positives in VOMS and mBESS in U.S. Army Special Operations Command (USASOC) personnel.

DESIGN

Cross-sectional study.

SETTING

Military medical clinic.

PARTICIPANTS

416 healthy USASOC personnel completed medical history, VOMS, and mBESS evaluations.

MAIN OUTCOME MEASURES

False positive rates for the VOMS (2+ on VOMS symptom item, ≥ 5 cm for near point of convergence [NPC] distance) and mBESS (total score >4) were determined using chi-square analyses and independent samples t-tests. Multivariable logistic regressions (LR) with adjusted odds ratios (aOR) were performed to identify risk factors for false positives on VOMS and mBESS. VOMS items false positive rates ranged from 10.6% (smooth pursuits) to 17.5% (NPC). mBESS total score false positive rate was 36.5%.

RESULTS

The multivariable LR model supported three significant predictors of VOMS false positives including age (OR= 1.07, 95% CI= 1.02-1.12, p=0.007), migraine (OR=2.49, 95% CI= 1.29-4.81, p=0.007), and motion sickness history (OR=2.46, 95% CI= 1.34-4.50, p=0.004). Results of the multivariable LR model supported only motion sickness history as a significant predictor (OR=2.34, 95% CI= 1.34-4.05, p=0.002) of mBESS false positives.

CONCLUSIONS

There were low false positive rates across VOMS items, which were associated with age, history of mTBI, migraine, and motion sickness. False positives for the mBESS total score were higher (36.5%) and were only associated with a history of motion sickness. These risk factors for false positives should be considered when administering and interpreting VOMS and mBESS components of the MACE-2 in this population.

Network Analysis of Research on Mild Traumatic Brain Injury in US Military Service Members and Veterans During the Past Decade (2010-2019)

OBJECTIVE

To evaluate trends in the extant literature on mild traumatic brain injury (mTBI) in military service members and veterans using network analysis based on a comprehensive search of original, peer-reviewed research articles involving human participants published between January 1, 2010, and December 31, 2019. Specifically, we employed network analysis to evaluate associations in the following areas: (1) peer-reviewed journals, (2) authors, (3) organizations/institutions, and (4) relevant key words.

PARTICIPANTS

Included studies were published in peer-reviewed journals available on Web of Science database, using US military service members or veterans.

DESIGN

Bibliometric network analytical review.

MAIN MEASURES

Outcomes for each analysis included number of articles, citations, total link strength, and clusters.

RESULTS

The top publishing journals were (1) Journal of Head Trauma and Rehabilitation, (2) Military Medicine, (3) Brain Injury, (4) Journal of Neurotrauma, and (5) Journal of Rehabilitation Research and Development. The top publishing authors were (1) French, (2) Lange, (3) Cooper, (4) Vanderploeg, and (5) Brickell. The top research institutions were (1) Defense and Veterans Brain Injury Center, (2) Uniformed Services University of the Health Sciences, (3) University of California San Diego, (4) Walter Reed National Military Medical Center, and (5) Boston University. The top co-occurring key words in this analysis were (1) posttraumatic stress disorder (PTSD), (2) persistent postconcussion symptoms (PPCS), (3) blast injury, (4) postconcussion syndrome (PCS), and (5) Alzheimer's disease.

CONCLUSIONS

The results of this network analysis indicate a clear focus on veteran health, as well as investigations on chronic effects of mTBI. Research in civilian mTBI indicates that delaying treatment for symptoms and impairments related to mTBI may not be the most precise treatment strategy. Increasing the number of early, active, and targeted treatment trials in military personnel could translate to meaningful improvements in clinical practices for managing mTBI in this population.

A trait of mind: stability and robustness of sleep across sleep opportunity manipulations during simulated military operational stress

STUDY OBJECTIVES

Within-subject stability of certain sleep features across multiple nights is thought to reflect the trait-like behavior of sleep. However, to be considered a trait, a parameter must be both stable and robust. Here, we examined the stability (i.e., across the same sleep opportunity periods) and robustness (i.e., across sleep opportunity periods that varied in duration and timing) of different sleep parameters.

METHODS

Sixty-eight military personnel (14 W) spent 5 nights in the sleep laboratory during a simulated military operational stress protocol. After an adaptation night, participants had an 8-hour sleep opportunity (23:00-07:00) followed by 2 consecutive nights of sleep restriction and disruption which included two 2-hour sleep opportunities (01:00-03:00; 05:00-07:00) and, lastly, another 8-hour sleep opportunity (23:00-07:00). Intra-class correlation coefficients were calculated to examine differences in stability and robustness across different sleep parameters.

RESULTS

Sleep architecture parameters were less stable and robust than absolute and relative spectral activity parameters. Further, relative spectral activity parameters were less robust than absolute spectral activity. Absolute alpha and sigma activity demonstrated the highest levels of stability that were also robust across sleep opportunities of varying duration and timing.

CONCLUSIONS

Stability and robustness varied across different sleep parameters, but absolute NREM alpha and sigma activity demonstrated robust trait-like behavior across variable sleep opportunities. Reduced stability of other sleep architecture and spectral parameters during shorter sleep episodes as well as across different sleep opportunities has important implications for study design and interpretation.