The effect of age on baseline neurocognitive performance.

OBJECTIVE: Evaluate the independent effect of age on baseline neurocognitive performance. STUDY DESIGN: Baseline ImPACT scores from tests taken by 7454 athletes aged 12-22 from 2009 to 2019 were split into three age cohorts: 12-14 years (3244), 15-17 years (3732), and 18-22 years (477). Linear regression analyses were used to evaluate the effect of age on ImPACT composite scores while controlling for demographic differences, medication-use, and symptom burden. Significance values have been set at p < 0.05. RESULTS: Linear regression analyses demonstrated that increased age does not significantly affect symptom score (ß = 0.06, p = 0.54) but does improve impulse control (ß = -0.45, p < 0.0001), verbal memory (ß = 0.23, p = 0.03), visualmotor (ß = 0.77, p < 0.0001), and reaction time (ß = -0.008, p < 0.0001) scores.  However, age did not have an effect on visual memory scores (ß = -0.25, p = 0.07). CONCLUSIONS: Age was shown to be an independent modifier of impulse control, verbal memory, visual motor, and reaction time scores but not visual memory or symptom scores.  This underscores the previous literature showing developmental differences as age increases among the adolescent athlete population.  This data also indicates the need for repeat neurocognitive baseline testing every other year as baseline scoring is likely to change as athletes become older.

High altitude modulates concussion incidence, severity, and recovery in young athletes.

BACKGROUND: High altitude may affect concussion, but prior studies are limited . We tested whether high altitude affects sport-related concussion (SRC) incidence, severity, and recovery. METHODS: Twenty-five thousand eight hundred fifteen baseline and post-injury Immediate Post-Concussion Assessment and Cognitive Testing results were compiled from Florida and Colorado, low (27 m or 62 m) and high (1,640 m or 1,991 m) altitude locations, respectively. Incidence, severity, and recovery of injury were compared between altitudes. RESULTS: High altitude was associated with increased suspected concussion incidence (adjusted OR, 2.04 [95% CI, 1.86 to 2.24];P < .0001). However, high altitude was associated with lower concussion severity measured by Severity Index (SI) (adjusted OR, 0.42 [95% CI, 0.37 to 0.49];P < .0001). High altitude was associated with decreased recovery from post-concussive symptoms in the migraine (ß, -2.72 [95% CI, -3.31 to -2.13]; P < .0001), cognitive (ß, -1.88 [95% CI, -2.40 to -1.36]; P < .0001), and sleep symptom clusters (ß, -0.30 [95% CI, -0.52 to -0.08]; P = .007). Athletes with initial SI≥8 showed prolonged neurocognitive dysfunction at high altitude (HR, 1.38 [95% CI, 1.06 to 1.81]; P = .02). CONCLUSIONS: High altitude was associated with increased suspected concussions and prolonged recovery but less severe initial injury.

Effects of a history of headache and migraine treatment on baseline neurocognitive function in young athletes.

OBJECTIVE/BACKGROUND: Despite the prevalence of concussions in young athletes, the impact of headaches on neurocognitive function at baseline is poorly understood. We analyze the effects of a history of headache treatment on baseline ImPACT composite scores in young athletes. METHODS: A total of 11,563 baseline ImPACT tests taken by 7,453 student-athletes ages 12-22 between 2009 and 2019 were reviewed. The first baseline test was included. There were 960 subjects who reported a history of treatment for headache and/or migraine (HA) and 5,715 controls (CT). The HA cohort included all subjects who self-reported a history of treatment for migraine or other type of headache on the standardized questionnaire. Chi-squared tests were used to compare demographic differences. Univariate and multivariate regression analyses were used to assess differences in baseline composite scores between cohorts while controlling for demographic differences and symptom burden. RESULTS: Unadjusted analyses demonstrated that HA was associated with increased symptoms (ß=2.30, 95% CI: 2.18-2.41, p<.0001), decreased visual memory (ß=-1.35, 95% CI: -2.62 to -0.43, p=.004), and increased visual motor speed (ß=0.71, 95% CI: 0.23-1.19, p=.004) composite scores. Baseline scores for verbal memory, reaction time, and impulse control were not significantly different between cohorts. Adjusted analyses demonstrated similar results with HA patients having greater symptom burden (ß=1.40, 95% CI: 1.10-1.70, p<.0001), lower visual memory (ß=-1.25, 95% CI: -2.22 to -0.27, p=.01), and enhanced visual motor speed (ß=0.60, 95% CI: 0.11-1.10, p=.02) scores. CONCLUSION: HA affected symptom, visual motor speed, and visual memory ImPACT composite scores. Visual memory scores and symptom burden were significantly worse in the HA group while visual motor speed scores were better, which may have been due to higher stimulant use in the HA group. The effects of HA on visual motor speed and visual memory scores were independent of the effects of the increased symptom burden.

Neurocognitive test performance and symptom reporting in cheerleaders with concussions.

OBJECTIVE: To evaluate neurocognitive test results and symptom reporting after sports-related concussion in a group of female cheerleaders. STUDY DESIGN: Junior and senior high school female cheerleaders (n = 138) underwent preparticipation baseline testing and repeated the ImPACT (Immediate Postconcussion Assessment and Cognitive Testing) evaluation within 7 days of concussive injury (range, 0-7 days; mean, 3.9 days). Postinjury neurocognitive and symptom scores were compared with preinjury (baseline) scores. "Abnormal" test performance was determined statistically using Reliable Change Index scores and self-reported symptoms. Main outcome variables included the composite scores indices from the ImPACT test, as well as symptoms reported by participants. Preinjury baseline and postinjury test results were compared using MANOVA. RESULTS: As a group, cheerleaders with concussion evaluated within 7 days of injury performed poorly on the ImPACT test battery relative to their own baseline (F = 6.5; P = .00). In addition, 61% of the cheerleaders with concussions reported an increase in symptoms compared with baseline. The groups did not differ significantly by position on the squad (F = 0.37; P = .96). Of the group of cheerleaders who did not report increased symptoms at the time of postinjury evaluation, 37% had at least 1 abnormal ImPACT composite score result, suggesting some residual cognitive decline compared with baseline. CONCLUSION: The diagnosis and management of concussion in cheerleaders should not consist solely of self-reported symptoms. Neurocognitive test results represent an important component of the evaluation process and may identify athletes with residual neurocognitive deficits who report being clinically asymptomatic.

Post-exertion neurocognitive test failure among student-athletes following concussion.

OBJECTIVE: The purpose of the present study was to examine post-exertion (PE) neurocognitive performance among student-athletes following concussion who were asymptomatic and returned to baseline normal neurocognitive test levels at rest. This study examined the neurocognitive performance of a sub-set of student-athletes who 'failed' to perform at baseline levels of neurocognitive function, i.e. exhibited downward reliable change index (RCI) alterations following a moderate exertional protocol during recovery from concussion. METHOD: A retrospective records review was carried out of Immediate Post-concussion Assessment and Cognitive Testing (ImPACT) and neuropsychological consultation data among athletes with sports-related concussion from a network of 22 schools and one junior hockey programme. RESULTS: Fifty-four student-athletes met inclusion criteria and participated in the study. A total of 27.7% of concussed student-athletes who were symptom-free and returned to baseline on ImPACT at rest (i.e. no longer demonstrated performance deficits on neurocognitive tests) exhibited cognitive decline following moderate physical exertion. The PE cognitive changes were not simply general performance effects, but significant changes in memory ability in the presence of intact processing speed functions. The PE-Pass and PE-Fail groups did not, however, differ on post-concussive symptoms or concussion history. CONCLUSIONS: Clinicians' return-to-play evaluation protocols should include post-exertional computerized neurocognitive testing.

Impact of Psychiatric Illnesses and Selective Serotonin Reuptake Inhibitor Medications on Baseline Neurocognitive Testing.

INTRODUCTION: Neurocognitive tests are an integral component of sport-related concussion (SRC) workup. A history of psychiatric illness (HPI) is common among young athletes. Investigations of factors that influence athletes' baseline neurocognitive function are crucial for an accurate assessment of SRC. OBJECTIVE: In this study, we aim to elucidate the effect of HPI and selective-serotonin reuptake inhibitor (SSRI) medication use on baseline neurocognitive performance in young athletes. METHODS: We conducted a retrospective cross-sectional study of Immediate Post-Concussion Assessment and Cognitive Testing assessments. A total of 268 athletes with HPI and a control group of 6,364 athletes were included. The outcomes were total symptom score based on post-concussion symptom scale, verbal memory, visual memory, visual motor, reaction time, and impulse control scores with self-reported HPI status and SSRI use. RESULTS: Athletes with HPI had an elevated symptom score in both univariate analysis (p < .0001) and multivariate analysis (p < .0001). HPI influence on visual memory score was not robust to multivariate analysis (p = .24). Athletes with HPI who reported SSRI medication use had the same baseline neurocognitive performance as other athletes with HPI. HPI influences athletes' baseline neurocognitive performance by elevating symptom scores. HPI does not alter any of the objective neurocognitive composite scores in contrast to previous work. CONCLUSIONS: Clinicians should consider the impact of HPI on baseline neurocognitive performance during the assessment of a suspected SRC. Additional research is required to bolster our findings on SSRI use and ascertain the effects of other drug classes on baseline neurocognitive performance.

Sport Contact Level Affects Post-Concussion Neurocognitive Performance in Young Athletes.

OBJECTIVE: Contact level affects the incidence of sports-related concussion. However, the effects of contact level on injury severity and recovery are less clear and are the focus of this study. METHOD: Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT) for athletes aged 12-22 was performed at baseline (n = 10,907 for 7,058 athletes), after suspected concussion determined by physicians or athletic trainers (n = 5,062 for 4,419 athletes), and during follow-up visits (n = 3,264 for 2,098 athletes). Athletes played contact/collision (CC), limited contact (LC), and noncontact (NC) sports. Injury incidence, severity, and recovery were measured using raw and change from baseline neurocognitive test scores. Comparisons between groups used univariate analysis and multivariable regression controlling for demographic variables. RESULTS: Compared to CC athletes, LC and NC athletes showed decreased suspected concussion incidence. At initial post-injury testing, all neurocognitive test scores were similar between groups except changes from baseline for processing speed were improved for LC compared to CC athletes. Upon follow-up testing, raw neurocognitive scores were better for NC compared to the contact collision athletes in verbal memory, processing speed, total symptom score, migraine cluster, cognitive cluster, and neuropsychiatric cluster scores. For change from baseline scores, LC athletes exhibited better performance on verbal memory, processing speed, and reaction time but also showed higher neuropsychiatric scores than CC athletes. CONCLUSION: Neurocognitive scores between contact levels were similar at the first post-injury test. However, follow up showed many improved scores and symptoms for limited and NC sports compared to CC sports, which may indicate faster recovery.

Incidence and Severity of Concussions Among Young Soccer Players Based on Age, Sex, and Player Position.

BACKGROUND: Previously studied risk factors for sports-related concussion in soccer players include sex, age, and player position. However, prior studies were limited in number, they reported conflicting results, and most did not assess initial concussion severity. PURPOSE/HYPOTHESIS: The purpose of this study was to conduct an in-depth analysis of soccer players across key demographic groups (sex, age, position) for both concussion incidence and severity. It was hypothesized that concussion incidence and severity would be higher among male players, players aged ≥17 years, and goalkeepers. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: The authors analyzed baseline and postinjury ImPACT (Immediate Post-Concussion Assessment and Cognitive Testing) scores for athletes aged 12 to 22 years between July 2009 and June 2019. Players were assigned to an age group based on when they had their most recent baseline test. Concussion incidence and concussion severity index were compared using t tests and multivariate logistic regression. RESULTS: For 1189 individuals who reported soccer as their primary sport, 1032 contributed 1754 baseline ImPACT tests (some individuals had multiple baseline tests), whereas 445 individuals were suspected of sustaining a concussion and then referred for a postinjury 1 test. Of these players, 254 (24.6%) had both a baseline and a postinjury test and were analyzed for concussion severity. Linear regression showed that forwards had a lower incidence of ImPACT-proxied concussions than goalkeepers had (P = .008). Female players had a significantly higher incidence of ImPACT concussions compared with male players (mean, 0.07 [female] vs 0.04 [male] concussions per person-year; P = .05). Players in the ≥17-year age group had a higher incidence of ImPACT concussions than players in the 15- to 16-year age group (P = .04), although the 15- to 16-year age group had more severe concussions than the ≥17-year age group (mean severity index, 2.91 [age 15-16 years] vs 1.73 [age ≥17 years]; P = .001). CONCLUSION: Female soccer players experienced a higher incidence of concussion than did male players, and goalkeepers experienced a greater incidence of ImPACT concussions than did forwards. Players of both sexes and all positions in the 15- to 16-year age group showed increased initial concussion severity compared with the ≥17-year age group, despite a lower comparative incidence of ImPACT concussions. Further study is needed to understand whether sex and player position affect concussion severity.

Psychometric data for the NFL neuropsychological test battery.

As part of a comprehensive league-wide study of concussion, the National Football League's Committee on Mild Traumatic Brain Injury sponsored a neuropsychological testing program from 1996 through 2001. Nearly 1,000 athletes participated voluntarily in the study. Traditional paper-and-pencil neuropsychological tests were used for baseline assessment. Neuropsychological tests used in the study included the Hopkins Verbal Learning Test-Revised, the Brief Visuospatial Memory Test-Revised, Trail-Making Tests (Parts A and B), and the Controlled Oral Word Association Test. We present a factor analysis of these baseline data on 513 athletes who completed all of the neuropsychological tests and present normative psychometric data on the multiple baseline tests employed.

Vestibular rehabilitation for dizziness and balance disorders after concussion.

BACKGROUND AND PURPOSE: Management of dizziness and balance dysfunction is a major challenge after concussion. The purpose of this study was to examine the effect of vestibular rehabilitation in reducing dizziness and to improve gait and balance function in people after concussion. METHODS: A retrospective chart review of 114 patients (67 children aged 18 years and younger [mean, 16 years; range, 8-18 years]; 47 adults older than 18 years [mean, 41 years; range, 19-73 years]) referred for vestibular rehabilitation after concussion was performed. At the time of initial evaluation and discharge, recordings were made of outcome measures of self-report (eg, dizziness severity, Activities-specific Balance Confidence Scale, and Dizziness Handicap Inventory) and gait and balance performance (eg, Dynamic Gait Index, gait speed, and the Sensory Organization Test). A mixed-factor repeated-measures analysis of variance was used to test whether there was an effect of vestibular rehabilitation therapy and age on the outcome measures. RESULTS: The median length of time between concussion and initial evaluation was 61 days. Of the 114 patients who were referred, 84 returned for at least 1 visit. In these patients, improvements were observed in all self-report, gait, and balance performance measures at the time of discharge (P < .05). Children improved by a greater amount in dizziness severity (P = .005) and conditions 1 (eyes open, fixed support) and 2 (eyes closed, fixed support) of the Sensory Organization Test (P < .025). DISCUSSION: Vestibular rehabilitation may reduce dizziness and improve gait and balance function after concussion. For most measures, the improvement did not depend on age, indicating that vestibular rehabilitation may equally benefit both children and adults. CONCLUSIONS: Vestibular rehabilitation should be considered in the management of individuals post concussion who have dizziness and gait and balance dysfunction that do not resolve with rest.

Assessing the predictive value of primary evaluation with the Immediate Post-Concussion Assessment and Cognitive Test following head injury.

OBJECTIVE: Concussions are a major public health concern, especially for high school and college student athletes. However, there are few prognostic metrics that can accurately quantify concussion severity in order to anticipate recovery time and symptom regression. The Immediate Post-Concussion Assessment and Cognitive Test (ImPACT) is a widely used neurocognitive assessment that can diagnose and track recovery from concussions. This study assesses whether initial ImPACT scores, collected within 48 hours of the injury, can predict persistence of concussion at follow-up. METHODS: Results from 6912 ImPACT tests were compiled in 2161 unique student athletes, ages 12-22 years. The authors defined a novel metric, the Severity Index (SI), which is a summation of the number of standard deviations from baseline at the 80% CI for each of the 5 composite scores reported by ImPACT. Patients were binned into groups based on SI (0-3.99, 4-7.99, 8-11.99, 12+) and the relationships between SI groups, composite scores, symptom profiles, and recovery time were characterized using 1-way and 2-way ANOVAs and Kaplan-Meier plots. A logistic regression assessed the value of SI for predicting concussion at follow-up. RESULTS: Patients with a higher SI at diagnosis were more likely to still be concussed at their first follow-up (F3,2300 = 93.06; p < 0.0001). Groups with a higher SI also displayed consistently slower recovery over a 42-day period and were more likely to report symptoms in all 4 symptom clusters (Migraine, Cognition, Sleep, and Neuropsychiatric). When controlling for sex, age, number of previous concussions, days between assessments, and location, SI significantly increased the odds of being concussed at follow-up (OR 1.122, 95% CI 1.088-1.142; p < 0.001). This model showed good discrimination with an area under the curve of 0.74. CONCLUSIONS: SI is a useful prognostic tool for assessing head injury severity. Concussions with higher initial SI tend to last longer and have broader symptomatic profiles. These findings can help patients and providers estimate recovery based on similar ImPACT score profiles.

Neurocognitive and symptom predictors of recovery in high school athletes.

OBJECTIVES: The purpose of this study was to identify specific symptom and neuropsychological test patterns that might serve as prognostic indicators of recovery in concussed high school football players. The recently proposed simple versus complex concussion classification was examined and specific symptom clusters were identified. DESIGN: Case-control study. SETTING: High school football. PARTICIPANTS: Subjects were 108 recently concussed male high school football athletes between the ages of 13 and 19 (mean, 16.01) years. ASSESSMENT OF RISK FACTORS: Participants were evaluated by utilizing the Immediate Postconcussion Assessment and Cognitive Testing computer-based neurocognitive test battery at before injury and within an average of 2.23 days of injury. All athletes were followed until they met criteria for clinical recovery. MAIN OUTCOME MEASURES: Symptom ratings and neurocognitive test performance. RESULTS: Both neurocognitive test results and self-reported symptom data had prognostic value in determining time to clinical recovery. Self-reported cognitive decline, Immediate Postconcussion Assessment and Cognitive Testing reaction time, and migraine headache symptoms were associated with longer time to clinical recovery. Overall, these difficulties were predictive of concussions that were retrospectively classified as complex. CONCLUSIONS: Specific symptom clusters and neurocognitive test results may have predictive value to classifying and managing concussions.

Computerized neuropsychological profiles of South African versus US athletes: a basis for commentary on cross-cultural norming issues in the sports concussion arena.

Computerized programs are widely used as part of the overall medical management of concussion in order to monitor recovery and facilitate safe return-to-play decisions. Typically, neurocognitive profiles of concussed athletes are compared with baseline and/or normative data in the absence of baseline scores. However, the cultural equivalence of performance on neuropsychological tests cannot be assumed and has not been sufficiently researched. The purpose of this study was to investigate the neuropsychological test profiles of the ImPACT (Immediate Postconcussion Assessment and Cognitive Testing) on age-matched South African (SA) rugby and US football players. Participants included 11 257 English-speaking, predominantly white male athletes from multiple SA and US schools and sports organizations in 3 age groups: 11 to 13 years (SA, n = 301; US, n = 775); 14 to 16 years (SA, n = 997; US, n = 4081); and 17 to 21 years (SA, n = 319; US, n = 4784). ImPACT neurocognitive composite scores (verbal and visual memory, visual motor speed, reaction time, impulse control) and the ImPACT total symptom score, derived from the initial baseline testing, were used for comparison purposes between the targeted groups. Independent t-test comparisons revealed overall equivalence between the SA and US athletes on the neurocognitive measures, but they also revealed consistently higher symptom scores for SA athletes in association with clinically relevant effect sizes. It was concluded that US neurocognitive normative data on the ImPACT test are appropriate for use on South African athletes whose first language is English, whereas culture-specific sensitivity for symptom reporting on this same population should be taken into consideration for management purposes. It is argued that neurocognitive equivalence is less likely to apply in educationally disadvantaged populations. The use of registered psychologists is deemed necessary to provide contextualized interpretations of computerized test scores, thereby protecting against misdiagnosis that may occur within the concussion management arena via actuarial approaches that fail to take sociocultural complexities into account.

The Effect of Game Importance on Concussion Incidence in the National Football League: An Observational Study.

Introduction Concussion incidence in the National Football League (NFL) has been shown to generally increase as the season progresses. Yet, there is evidence that suggests that the incidence stagnates or decreases in the final quarter of the season in comparison to the third quarter. This anomaly cannot be explained by any of the known modulators of concussion incidence. However, the fact that the teams start getting eliminated from playoff contention in the fourth quarter of the season may explain this pattern in concussion incidence. This study tests whether there is a difference in concussion incidence in games between teams who are still in the playoff hunt [in the hunt (IH) games] versus games where both teams have had their playoff fate already determined (non-IH games). Methods We obtained details of 166 documented concussions from weeks 13-16 of each of the four NFL seasons from 2012 to 2015 from Public Broadcasting Service's (PBS) Frontline Concussion Watch and matched them to the games in which they occurred. Each game was categorized based on the playoff status [clinched (CL), eliminated (EL), or IH] of the teams playing in the game. Concussion incidence of the game types was compared to each other using a one-way analysis of variance (ANOVA) test and student t-tests. Additionally, concussion incidences at six different player positions in important games were compared to the corresponding incidences in unimportant games. An ordinary least squares regression was used to examine the effects of game importance and plays per game on concussion incidence. Results Concussion incidence in important games (mean = 0.651 ±0.055) did not differ significantly (p: 0.890) from the incidence in unimportant games (mean = 0.623 ±0.143). Instead, plays per game was found to be the primary driver of concussion in the regression analysis (ß = 0.01605; p: 0.025). At the position-specific level, running backs (RB) were the only position to demonstrate a significant increase in concussion incidence (p: 0.004) in important games (mean = 0.049 ±0.017) compared to unimportant games (mean = 0.00 ±0.00). Conclusions The results suggest that, in general, players are not more likely to suffer concussions in IH games than in non-IH games. However, RBs may have an increased risk of concussion in games with playoff implications than in games without.

Concussion management in the child and adolescent athlete.

This article reviews the status of concussion management in child and adolescent athletes. Children and adolescent athletes represent a distinct group from adult athletes, although past concussion guidelines have not specifically addressed these differences. It is the position of this article that younger athletes need to be considered as a separate group and that conservative management of concussion is often called for. Neurodevelopmental differences between adult and child athletes are highlighted and new developments in the management of concussion in youth sports are discussed.

Does the Environment Influence the Frequency of Concussion Incidence in Professional Football?

Background Sports-related concussion is a major cause of mild traumatic brain injury (mTBI). It is possible that environmental factors, such as temperature, humidity, and stadium's altitude, may influence the overall incidence of concussions during a game. Purpose To examine the impact of environmental factors, such as temperature, humidity, barometric pressure, and dew point, on concussion incidence. Methods Public Broadcasting Service (PBS) FRONTLINE Concussion Watch was used to collect injury data on 32 NFL teams during regular season games from 2012 to 2015. Weather data points were collected from Weather Underground. Concussion incidence per game, the probability of a concussion during a game, and a difference in mean game-day temperature, humidity, dew point, and barometric pressure between concussion and concussion-free games were calculated. Our analysis included t-tests, analysis of variance (ANOVA), multivariate correlation tests, and logistic and Poisson regression.  Results Overall, 564 concussions were reported. There were 411 games with concussions and 549 games without concussions. We observed a significant decrease in concussion incidence with increasing temperature, both when the temperature was divided into 20oF increments or into quartiles (p = 0.005 and p = 0.002, respectively). We identified a statistically significant lower mean-game day temperature in concussion games compared to concussion-free games (p < 0.0006). We also observed a significant decrease in the incidence of concussion per game with increasing dew point. There was no significant difference in concussion incidence in barometric pressure and humidity. The logistic regression model predicted a decrease in the probability of a concussion in games with higher temperatures and dew points. Conclusions National Football League (NFL) players experienced an increased risk of concussion during football games played in colder temperatures and at lower dew points. Further research on environmental effects on concussions may aid in improving player safety in football leagues.

ETHOS - an effective theory of structure formation: predictions for the high-redshift Universe - abundance of galaxies and reionization.

We contrast predictions for the high-redshift galaxy population and reionization history between cold dark matter (CDM) and an alternative self-interacting dark matter model based on the recently developed ETHOS framework that alleviates the small-scale CDM challenges within the Local Group. We perform the highest resolution hydrodynamical cosmological simulations (a 36 Mpc3 volume with gas cell mass of ∼ 105 M⊙ and minimum gas softening of ∼ 180 pc) within ETHOS to date - plus a CDM counterpart - to quantify the abundance of galaxies at high redshift and their impact on reionization. We find that ETHOS predicts galaxies with higher ultraviolet (UV) luminosities than their CDM counterparts and a faster build-up of the faint end of the UV luminosity function. These effects, however, make the optical depth to reionization less sensitive to the power spectrum cut-off: the ETHOS model differs from the CDM τ value by only 10 per cent and is consistent with Planck limits if the effective escape fraction of UV photons is 0.1-0.5. We conclude that current observations of high-redshift luminosity functions cannot differentiate between ETHOS and CDM models, but deep James Webb Space Telescope surveys of strongly lensed, inherently faint galaxies have the potential to test non-CDM models that offer attractive solutions to CDM's Local Group problems.

Effects of Game Characteristics and Player Positions on Concussion Incidence and Severity in Professional Football.

BACKGROUND: Increasing efforts have been made to reduce the incidence and severity of concussion in high-contact sports. Despite these efforts, a relative lack of knowledge is available regarding modulating factors affecting concussion injury. PURPOSE: To analyze the potential influence of game characteristics and outcomes on concussion incidence and severity in professional football. STUDY DESIGN: Descriptive epidemiology study. METHODS: PBS Frontline Concussion Watch was used to collect concussion injury data from regular-season games of 32 National Football League (NFL) teams from 2012 to 2015. Game characteristic variables such as rushing and passing attempts, turnovers, and margin of victory were collected from ESPN. Analysis included descriptive statistics, analysis of variance, t tests, and correlation tests. RESULTS: Away teams demonstrated a significantly greater concussion incidence per game than home teams. Losing teams had a significantly greater concussion incidence per game than winning teams. Being both the away team and the losing team appeared to have an additive effect. The home-versus-away and win-versus-loss effects were significant for offensive but not defensive positions. Within individual positions, significantly greater concussion incidence was associated with tight ends, running backs, wide receivers, and cornerbacks. When running versus passing positions were compared, passing positions (wide receiver, tight end, cornerback, safety) had significantly greater concussion incidence. A total of 626 games were missed as a result of reported concussions. Away teams had significantly more games missed due to concussion when they lost. Play time did not significantly differ before or after concussion injury. Other game characteristic variables did not significantly affect concussion frequency or intensity. CONCLUSION: Position, game location, and game outcome affect concussion incidence for professional football players. In a subset of analyses, the number of games missed aligned with concussion incidence, but this appeared to be an imperfect measure. These findings highlight new factors that may modulate concussion incidence and merit further study on how they may influence concussion evaluation.

Neuropsychological evaluation in the diagnosis and management of sports-related concussion.

A mild traumatic brain injury in sports is typically referred to as a concussion. This is a common injury in amateur and professional athletics, particularly in contact sports. This injury can be very distressing for the athlete, his or her family, coaches, and school personnel. Fortunately, most athletes recover quickly and fully from this injury. However, some athletes have a slow recovery, and there are reasons to be particularly concerned about re-injury during the acute recovery period. Moreover, some athletes who have experienced multiple concussions are at risk for long-term adverse effects. Neuropsychologists are uniquely qualified to assess the neurocognitive and psychological effects of concussion. The National Academy of Neuropsychology recommends neuropsychological evaluation for the diagnosis, treatment, and management of sports-related concussion at all levels of play.

The relation between post concussion symptoms and neurocognitive performance in concussed athletes.

The objective of this study was to examine differences in neurocognitive performance between symptomatic concussed athletes, a group of concussed athletes with no subjective symptoms, and a non-concussed control group of athletes. All concussed athletes were evaluated within one week of injury using the ImPACT computerized test battery. Results indicate that concussed athletes who denied subjective symptoms demonstrated poorer performance than control subjects on all four composite scores of the ImPACT test batters (Verbal Memory, Visual Memory, Reaction Time and Processing Speed However, the concussed but asymptomatic group demonstrated significantly better performance than did the concussed and symptomatic group. Thus, concussed athletes who did not report subjective symptoms were not fully recovered based on neurocognitive testing. This study underscores the importance of neurocognitive testing in the assessment of concussion sequelae and recovery.