Sports-Related Concussion Affects Cognitive Function in Adolescents: A Systematic Review and Meta-analysis.

BACKGROUND: Rates of sports-related concussion (SRC) are high in adolescents. Ambiguity exists regarding the effect of SRC on cognitive function in adolescents. PURPOSE: To rigorously examine adolescents' cognitive function after SRC. STUDY DESIGN: Systematic review and meta-analysis; Level of evidence, 4. METHODS: Web of Science, Scopus, and PubMed were searched from database inception until September 2021. Studies were included if participants were adolescents aged 13 to 18 years, if the definition of SRC was fully consistent with the Berlin Consensus Statement on Concussion in Sport, if the study included a control group or in-group baseline test, and if the study reported cognitive outcomes (eg, visual memory, processing speed) that could be separately extracted. RESULTS: A total of 47 studies were included in the systematic review, of which 31 were included in the meta-analysis, representing 8877 adolescents with SRC. Compared with individuals in the non-SRC group, individuals with SRC had worse performance in cognitive function and reported more symptoms not only in the acute phase but also in the prolonged phase (1-6 months after injury) (visual memory: d = -0.21, 95% CI, -0.37 to -0.05, P = .012; executive function: d = -0.56, 95% CI, -1.07 to -0.06, P = .028; and symptoms: d = 1.17, 95% CI, 0.13 to 2.22, P = .028). Lower scores in most of the outcomes of cognitive function were observed at <3 days and at 3 to 7 days, but higher scores for verbal memory (d = 0.10; 95% CI, 0.03 to 0.17; P = .008) and processing speed (d = 0.17; 95% CI, 0.10 to 0.24; P < .001) were observed at 7 to 14 days after SRC relative to baseline. The effects of SRC on cognitive function decreased over time (100% of the variance in reaction time, P < .001; 99.94% of the variance in verbal memory, P < .001; 99.88% of the variance in visual memory, P < .001; 39.84% of the variance in symptoms, P = .042) in control group studies. Study design, participant sex, measurement tools, and concussion history were found to be modulators of the relationship between cognitive function and SRC. CONCLUSION: This study revealed that adolescent cognitive function is impaired by SRC even 1 to 6 months after injury. Results of this study point to the need for tools to measure cognitive function with multiple parallel versions that have demographically diversiform norms in adolescents. Effective prevention of SRC, appropriate treatment, and adequate evaluation of cognitive function before return to play are needed in adolescent SRC management. Moreover, caution is warranted when using the baseline-to-postconcussion paradigm in return-to-play decisions.

Factors Associated With Energy Expenditure and Energy Balance in Acute Sport-Related Concussion.

CONTEXT: Sport-related concussion (SRC) is characterized by a pathologic neurometabolic cascade that results in an increased intracranial energy demand and a decreased energy supply. Little is known about the whole-body energy-related effects of SRC. OBJECTIVE: To examine factors associated with whole-body resting metabolic rate (RMR), total energy expenditure (TEE), energy consumption (EC), and energy balance (EBal) in student-athletes acutely after SRC and healthy matched control individuals. DESIGN: Case-control study. SETTING: University research laboratory. PATIENTS OR OTHER PARTICIPANTS: Student-athletes diagnosed with SRC (n = 28, 50% female, age = 18.4 ± 1.8 years, body mass index [BMI] = 24.1 ± 4.1 kg/m2) assessed ≤72 hours postinjury and a matched control group (n = 28, 50% female, age = 19.4 ± 2.9 years, BMI = 24.7 ± 4.78 kg/m2). MAIN OUTCOME MEASURE(S): Resting metabolic rate was measured via indirect calorimetry. Participants reported their physical activity and dietary intake for 3 days, which we used to estimate TEE and EC, respectively, and to calculate EBal (EC:TEE ratio). Resting metabolic rate, TEE, and EC were normalized to body mass. Group and group-by-sex comparisons were conducted for RMR·kg-1, TEE·kg-1, EC·kg-1, and EBal using independent t tests with the a priori α = .05. Associations of age, sex, concussion history, BMI, and symptom burden with RMR·kg-1 and EBal were explored with linear regression models. RESULTS: Total energy expenditure·kg-1 was lower (P < .01; mean difference ± SD = -5.31 ± 1.41 kcal·kg-1) and EBal was higher (P < .01; 0.28 ± 0.10) in SRC participants than in control participants. Both sexes with SRC had lower TEE·kg-1 than did the control participants (P values ≤ .04); females with SRC had higher EBal than controls (P = .01), but male groups did not differ. Higher RMR·kg-1 was associated with history of concussion (adjusted R2 = .10, ß = 0.65). Younger age (ß = -0.35), fewer concussions (ß = -0.35), lower BMI (ß = -0.32), greater symptom duration (ß = 1.50), and lower symptom severity (ß = -1.59) were associated with higher EBal (adjusted R2 = .54). CONCLUSIONS: Total energy expenditure·kg-1 and EBal appeared to be affected by acute SRC, despite no differences in RMR·kg-1. Sex, concussion history, BMI, and symptom burden were associated with acute energy-related outcomes.

Chronic impairments of static postural stability associated with history of concussion.

Postural stability deficits are commonly observed in cases of concussion. However, the objective duration in which impairments of standing postural stability remain following a concussion is often inconclusive. The present study was conducted to determine if prior history of concussion is associated with deficits in postural stability beyond the clinical determination of recovery. It was hypothesized that concussion history would be associated with decreases in static stability compared to individuals that have never sustained a concussion. Fifty-four healthy adults were recruited based on whether they reported sustaining one or more prior concussions (n = 27) or no history of concussion (n = 27). Participants were instructed to stand on a force platform to track center-of-pressure (CoP) during standing for thirty seconds under four conditions based on stance and number of tasks: (1) bipedal, single-task, (2) bipedal, dual-task, (3) unipedal, single-task, and (4) unipedal, dual-task. Results revealed that individuals with a history of concussion demonstrate significantly reduced postural stability under dual-task conditions as evidenced by increases in average displacements and elliptical area of postural sway as well as reductions in CoP sample entropy. However, there were no significant differences in CoP displacement or elliptical area between groups under single task conditions. Overall, these findings indicate that concussion is associated with impairments of maintaining standing postural stability that remain evident approximately 7 years following clinical resolution of the initial injury. The exacerbation of these impairments under dual-task conditions indicate that concussion can result in a reduced capacity to allocate proper attention resources to multiple concurrent objectives.

Lifetime prevalence of concussion among Canadian ice hockey players aged 10 to 25 years old, 2014 to 2017.

BACKGROUND: The primary objective of this study was to identify the self-reported lifetime prevalence of diagnosed concussions among Canadian ice hockey players aged 10 to 25 years old. METHOD: Medical records were identified for n=5223 athletes whom completed comprehensive baseline assessments with a Canada-wide network of private concussion management clinics. Variables extracted included: sex, age, diagnosed history of and number of prior concussions, diagnosed health condition(s), and Post-Concussion Symptom Scale scores. RESULTS: Approximately 22% of all athletes, 21.7% of females and 21.8% of males reported that they had sustained at least one diagnosed concussion. Age was significantly associated with history of concussion as was having an additional health condition. Sex was not significantly associated with a history of concussion. CONCLUSION: Lifetime history of concussion prevalence estimates aligned closely with estimates previously published. Future investigations should seek to establish the prevalence of concussions that occur during ice hockey games and practices alone.

CONTEXTE: L'objectif principal de cette étude était de déterminer la prévalence autodéclarée au cours de la vie des commotions cérébrales diagnostiquées chez les joueurs canadiens de hockey sur glace âgés de 10 à 25 ans. MÉTHODE: Des dossiers médicaux ont été identifiés pour 5223 athlètes qui ont effectué des évaluations de base complètes avec un réseau pancanadien de cliniques privées de gestion des commotions cérébrales. Les variables extraites comprenaient : le sexe, l'âge, les antécédents diagnostiqués et le nombre de commotions cérébrales antérieures, le ou les problèmes de santé diagnostiqués et les scores de l'échelle des symptômes après la commotion cérébrale. RÉSULTATS: Environ 22 % de tous les athlètes, 21,7 % des femmes et 21,8 % des hommes ont déclaré avoir reçu au moins un diagnostic de commotion cérébrale. L'âge était associé de façon significative aux antécédents de commotion cérébrale tout comme le fait d'avoir un autre problème de santé. Le sexe n'était pas associé de façon significative à des antécédents de commotion cérébrale. CONCLUSION: Les estimations de la prévalence des antécédents de commotion cérébrale au cours de la vie concordent étroitement avec les estimations publiées antérieurement. Les enquêtes futures devraient chercher à établir la prévalence des commotions cérébrales qui surviennent uniquement pendant les parties et les pratiques de hockey sur glace.

Unravelling the interaction between the DRD2 and DRD4 genes, personality traits and concussion risk.

BACKGROUND: Concussion occurs when biomechanical forces transmitted to the head result in neurological deficits. Personality may affect the balance between safe and dangerous play potentially influencing concussion risk. Dopamine receptor D2 (DRD2) and dopamine receptor D4 (DRD4) genetic polymorphisms were previously associated with personality traits. OBJECTIVES: This case-control genetic association study investigated the associations of (1) DRD2 and DRD4 genotypes with concussion susceptibility and personality, (2) personality with concussion susceptibility and (3) the statistical model of genotype, personality and concussion susceptibility. METHODS: In total, 138 non-concussed controls and 163 previously concussed cases were recruited from high school (n=135, junior), club and professional rugby teams (n=166, senior). Participants were genotyped for DRD2 rs12364283 (A>G), DRD2 rs1076560 (C>A) and DRD4 rs1800955 (T>C) genetic variants. Statistical analyses including structural equation modelling were performed using the R environment and STATA. RESULTS: The rs1800955 CC genotype (p=0.014) and inferred DRD2 (rs12364283-rs1076560)-DRD4 (rs1800955) A-C-C allele combination (p=0.019) were associated with decreased concussion susceptibility in juniors. The rs1800955 TT and CT genotypes were associated with low reward dependence in juniors (p<0.001) and seniors (p=0.010), respectively. High harm avoidance was associated with decreased concussion susceptibility in juniors (p=0.009) and increased susceptibility in seniors (p=0.001). The model showed that a genetic variant was associated with personality while personality was associated with concussion susceptibility. CONCLUSION: These findings highlight the linear relationship between genetics, personality and concussion susceptibility. Identifying a genetic profile of 'high risk' behaviour, together with the development of personalised behavioural training, can potentially reduce concussion risk.

Physiological underarousal as a mechanism of aggressive behavior in university athletes with a history of concussion.

INTRODUCTION: Research has indicated that athletes who engage in high-risk athletic activities, such as football and hockey, have riskier personalities than their low-risk and nonathlete counterparts (Ahmadi et al., 2011, Procedia Soc Behav Sci, 30 and 247-251; Zuckerman, 1983, Biological bases of sensation seeking, impulsivity, and anxiety, Lawrence Erlbaum Assoc Inc.). For instance, increased sensation-seeking and aggression are common in high-risk athletes, rendering these individuals more likely to sustain a subsequent injury, such as concussion. Elevated levels of certain personality traits, including impulsivity and aggression, have also been observed after concussion (Goswami et al., 2016, Brain Struct Funct, 221 and 1911-1925). The purpose of this study therefore was to determine whether aggressive behavior in university athletes may be accounted for, in part, by a history of concussion, rather than exclusively athletic status. METHODS: Using a quasi-experimental design, 66 university students (n = 18 nonathletes, n = 24 low-risk athletes, n = 24 high-risk athletes) with (n = 27) and without a history of concussion (n = 39) completed the Buss & Perry Aggression Questionnaire (BPAQ; Buss & Perry, , J Pers Soc Psychol, 63 and 452) and provided electrodermal activation (EDA) as an index of physiological arousal. RESULTS: It was found that decreased physiological arousal among students with a history of concussion was associated with greater endorsement of physical aggression. Moreover, athletic status did not account for this pattern of aggression, as athletes and nonathletes did not differ in terms of self-reported aggressive tendencies. CONCLUSIONS: Physiological compromise after concussive injury may act as an independent mechanism of aggressive behavior in athletes beyond factors, such as athletic status.

Influences of Mental Illness, Current Psychological State, and Concussion History on Baseline Concussion Assessment Performance.

BACKGROUND: A student-athlete's mental state, including history of trait anxiety and depression, or current psychological state may affect baseline concussion assessment performance. PURPOSE: (1) To determine if mental illness (anxiety, depression, anxiety with depression) influences baseline scores, (2) to determine if psychological state correlates with baseline performance, and (3) to determine if history of concussion affects Brief Symptom Inventory-18 (BSI-18) subscores of state anxiety, depression, and somatization. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: A sample of 8652 collegiate student-athletes (54.5% males, 45.5% females) participated in the Concussion Assessment, Research and Education (CARE) Consortium. Baseline assessments included a demographic form, a symptom evaluation, Standardized Assessment of Concussion, Balance Error Scoring System, a psychological state assessment (BSI-18), and Immediate Post-concussion Assessment and Cognitive Test. Baseline scores were compared between individuals with a history of anxiety (n = 59), depression (n = 283), and anxiety with depression (n = 68) and individuals without a history of those conditions (n = 8242). Spearman's rho correlations were conducted to assess the relationship between baseline and psychological state subscores (anxiety, depression, somatization) (α = .05). Psychological state subscores were compared between individuals with a self-reported history of concussions (0, 1, 2, 3, 4+) using Kruskal-Wallis tests (α = .05). RESULTS: Student-athletes with anxiety, depression, and anxiety with depression demonstrated higher scores in number of symptoms reported (anxiety, 4.3 ± 4.2; depression, 5.2 ± 4.8; anxiety with depression, 5.4 ± 3.9; no anxiety/depression, 2.5 ± 3.4), symptom severity (anxiety, 8.1 ± 9.8; depression, 10.4 ± 12.4; anxiety with depression, 12.4 ± 10.7; no anxiety/depression, 4.1 ± 6.9), and psychological distress in state anxiety (anxiety, 3.7 ± 4.7; depression, 2.5 ± 3.6; anxiety with depression, 3.8 ± 4.2; no anxiety/depression, 0.8 ± 1.8), depression (anxiety, 2.4 ± 4.0; depression, 3.2 ± 4.5; anxiety with depression, 3.8 ± 4.8; no anxiety/depression, 0.8 ± 1.8), and somatization (anxiety, 2.3 ± 2.9; depression, 1.8 ± 2.8; anxiety with depression, 2.2 ± 2.4; no anxiety/depression, 0.9 ± 1.7). A moderate positive relationship existed between all BSI-18 subscores and total symptom number (n = 8377; anxiety: rs = 0.43, P < .001; depression: rs = 0.42, P < .001; somatization: rs = 0.45, P < .001), as well as total symptom severity (anxiety: rs = 0.43, P < .001; depression: rs = 0.41, P < .001; somatization: rs = 0.45, P < .001). Anxiety, depression, and somatization subscores were greater among student-athletes that self-reported more concussions. CONCLUSION: Clinicians should be cognizant that student-athletes with a history of trait anxiety, depression, and anxiety with depression may report higher symptom score and severity at baseline. Individuals with extensive concussion history may experience greater state anxiety, depression, and somatization.

Concussion: A History of Science and Medicine, 1870-2005.

OBJECTIVE: To review the intellectual history of concussion from the mid-19th century to the opening decade of the 21st century. BACKGROUND: Head injuries (HI) and their acute and long-term effects have been investigated for centuries, with major reviews of the topic appearing by 1870. Thus, while it has long been acknowledged that chronic traumatic encephalopathy was first described by Harrison Martland in 1928, an examination of the history of concussion research up to Martland's seminal report places his studies in a deeper historical context. This history makes clear that Martland's findings were one among many such studies showcasing the lasting dangers of blows to the head. In the years after Martland published his study, his paper was frequently cited in other papers that made clear that blows to the head, of all ranges of severity, were dangerous injuries with potentially life-changing consequences. METHODS: The author has engaged in an historical analysis of the development and elaboration of concussion research in clinical medicine, neurology, neurosurgery, and those scientific disciplines related to clinical medicine. The author has found numerous primary sources from the history of medicine and science that describe the acute and chronic effects of single and repeated sub-concussive and concussive blows to the head. RESULTS: This study makes clear that evidence-based methodologies inevitably short-change the knowledge of past clinicians and scientists by holding these figures to normative standards of recent invention. What criticism of this kind fails to recognize is that past investigators, many of them pioneers in their fields, published their work in ways that matched the highest normative standards of their day for the presentation of evidence. CONCLUSIONS: It has been recognized for a long time that concussions are dangerous injuries with potentially life-changing consequences, ranging from permanent symptoms to degenerative neurological states. The intellectual history of medicine and science from 1870 to the recent past shows both a continuity of clinical observations about HI and a steady, incremental accumulation of knowledge refining our understanding of those observations from a remarkably wide sphere of scientific disciplines.

Sub-concussive trauma, acute concussion, and history of multiple concussions: Effects on quiet stance postural control stability.

Although balance control has been studied extensively following acute concussion, little is known regarding repetitive sub-concussive head impacts or chronic exposure to multiple concussive events. Quiet stance postural control was characterized in contact sport athletes at pre-season (n = 135) and post-season (n = 48) to evaluate the effects of subconcussive trauma to the head. To determine the impact of acute concussion on postural control, athletes diagnosed with a concussion during the season (n = 12) were tested at 72-h, 2-weeks, and 1-month post-injury. Because only 4 of the concussed athletes completed baseline testing, control athletes (n = 12) matched for sport, age, body mass index (BMI), and previous concussion history served as a comparison group. Finally, the effects of previous concussion history on quiet stance postural control were determined by comparing pre-season data in contact sport athletes with either zero (Hx0, n = 50) or three or more (Hx3+, n = 25) previous concussions. A force plate was used to compare changes in centre-of-pressure root-mean-square displacement (RMSdisp) and mean-velocity (COPvel) in the anterior/posterior (AP) and medial/lateral (ML) directions. One-minute trials were performed with feet hip-width apart, hands-on-hips, and A) eyes-open and B) eyes-closed. Biomechanical head-impact exposure (impacts over 10 g) was indexed over the season using mastoid-fixed impact sensors. In acutely injured athletes, repeated-measures ANOVA revealed a significant effect of time for RMSdisp AP with increased displacement at 2 weeks compared to 72 h (p = 0.008, 95% CI: -0.180, -0.310 cm). No other COP variables were affected by acute concussion. Moreover, there was no effect of concussion history or repeated sub-concussive impacts on any quiet stance metric. Additionally, head-impact exposure metrics were not correlated with COP metrics. Taken together, the data suggests alterations in COP sway during quiet stance persist in the acute 2-week period after injury. These findings were not present with either a history of multiple concussions or exposure to sub-concussive head impacts indicating acute concussion does not have appear to have long term effects for these measures.

Effect of concussion history on symptom burden and recovery following pediatric sports-related concussion.

OBJECTIVE The aim of this study was to examine differences in symptom burden and duration until physician-documented clinical recovery among pediatric patients with sports-related concussion (SRC) with and without a history of concussion. METHODS A retrospective chart review was performed for all pediatric patients (7-19 years old) referred to the Pan Am Concussion Program in Winnipeg, Canada, with an SRC and evaluated < 30 days postinjury between September 1, 2013, and August 1, 2015. RESULTS A total of 322 patients with SRC (64.91% male, mean age 13.96 years) who were evaluated a median of 7 days (interquartile range [IQR] 5-11 days) postinjury were included. Patients without a history of concussion endorsed significantly fewer concussion symptoms at initial assessment (median 5.5 symptoms, IQR 1-10 symptoms) than those with a previous concussion (median 7 symptoms, IQR 2-13.25 symptoms; p = 0.036). The median Post-Concussion Symptom Scale scores were 9 (IQR 1-23) for patients with no concussion history and 13 (IQR 3-33) for those with a history of concussion (p = 0.032). For patients with no previous concussion, the median number of days until physician-documented clinical recovery was 23 (IQR 15-44 days) compared with 25 days (IQR 18-43 days) for those with a history of concussion (p = 0.281). There was no significant difference in the proportion of patients who experienced delayed time until physician-documented clinical recovery (> 1 month postinjury) between the groups (p = 0.584). CONCLUSIONS Although a history of concussion may be associated with increased symptom burden following pediatric SRC, there was no difference in the time until physician-documented clinical recovery. Pediatric patients with SRC who have a history of concussion should be managed on an individualized basis. Future work is needed to examine the short- and long-term effects of multiple concussions in children and adolescents.

A case matched study examining the reliability of using ImPACT to assess effects of multiple concussions.

BACKGROUND: Approximately 3.8 million sport and recreational concussions occur per year, creating a need for accurate diagnosis and management of concussions. Researchers and clinicians are exploring the potential dose-response cumulative effects of concussive injuries using computerized neuropsychological exams, however, results have been mixed and/or contradictory. This study starts with a large adolescent population and applies strict inclusion criteria to examine how previous mild traumatic brain injuries affect symptom reports and neurocognitive performance on the Immediate Post-concussion Assessment and Cognitive Testing (ImPACT) computerized tool. METHODS: After applying exclusion criteria and case matching, 204 male and 99 female participants remained. These participants were grouped according to sex and the number of previous self-reported concussions and examined for overall differences on symptoms reported and scores obtained on the ImPACT neurocognitive battery composites. In an effort to further reduce confounding factors due to the varying group sizes, participants were then case matched on age, sex, and body mass index and analyzed for differences on symptoms reported and scores obtained on the ImPACT neurocognitive battery composites. RESULTS: Case matched analysis demonstrated males with concussions experience significantly higher rates of dizziness (p = .027, η2 = .035), fogginess (p = .038, η2 = .032), memory problems (p = .003, η2 = .055), and concentration problems (p = .009, η2 = .046) than males with no reported previous concussions. No significant effects were found for females, although females reporting two concussions demonstrated a slight trend for experiencing higher numbers of symptoms than females reporting no previous concussions. CONCLUSIONS: The results suggest that male adolescent athletes reporting multiple concussions have lingering concussive symptoms well after the last concussive event; however, these symptoms were found to be conflicting and better explained by complainer versus complacent attitudes in the population examined. Our results conflict with a significant portion of the current literature that uses relatively lenient inclusion and exclusion criteria, providing evidence of the importance of strict inclusion and exclusion criteria and examination of confounding factors when assessing the effects of concussions.