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Abstract
Objective We sought to determine whether male collision sport athletes perform worse on computerised neurocognitive assessments and report higher symptom burdens than athletes in contact (but not collision) sports and athletes in non-contact sports.
Methods This cross-sectional study used data collected by the Massachusetts Concussion Management Coalition on high school boys who underwent computerised neurocognitive testing between 2009 and 2018. We divided sports participation in three different sport types: (1) collision, (2) contact, non-collision and (3) non-contact. Our outcomes included the four computerised neurocognitive composite scores (verbal memory, visual memory, visual motor speed and reaction time) and the total symptom score. The independent variable was sport type (collision, contact, non-contact), adjusted for age, concussion history and comorbidities.
Results Of the 92 979 athletes (age: 15.59±2.08 years) included in our study, collision sport athletes performed minimally but significantly worse than other athletes on neurocognitive composite scores (verbal memory: β=−1.64, 95% CI −1.85 to –1.44; visual memory: β=−1.87, 95% CI −2.14 to –1.60; visual motor speed: β=−2.12, 95% CI −2.26 to –1.97; reaction time: β=0.02, 95% CI 0.02 to 0.02). Collision and contact sport athletes also had slightly but significantly lower total symptom scores (collision: 3.99±7.17; contact: 3.78±6.81; non-contact: 4.32±7.51, p<0.001, η2=0.001) than non-contact sport athletes.
Conclusion There are minimal observed differences in performance on neurocognitive assessments between collision sport, contact sport and non-contact sport athletes. The repetitive subconcussive head impacts associated with collision sport participation do not appear to negatively affect self-reported symptoms or neurocognitive functioning in current youth athletes.
- CONCUSSION
- COGNITION
Data availability statement
All data relevant to the study are included in the article or uploaded as online supplemental information.
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Key messages
What is already known on this topic
Youth athletes participating in collision and contact sports may experience more repetitive head impacts, which have been theorised as a potential catalyst for later life cognitive problems. However, the relationship between these repetitive impacts, symptoms and cognitive functioning remains unknown at the high school level.
What this study adds
Negative consequences associated with boys playing collison sports were not detectable on cognitive testing or in self-reported symptoms.
How this study might affect research, practice and/or policy
These findings may potentially influence the recommendations surrounding adolescent participation in collision or contact sports.
Introduction
Nearly 8 million individuals in the USA participate in high school sports annually, with the number of participants rising each year. Collision and contact sports remain popular among high school boys.1 2 Adolescence is a critical period for brain development, particularly for executive functioning,3 and there is growing concern surrounding repetitive head impacts in youth sports and the resulting effects on brain health. The acute effects of concussion are reasonably understood, but the potential long-term repercussions remain debated.4
Beyond diagnosed concussions, some have suggested an association between repetitive subconcussive head impacts, those blows to the head that are not associated with the clinical signs or symptoms required for diagnosing a concussion, and both short-term and long-term neurological impairments. Some studies have reported cognitive decline and brain alterations, both functional and microstructural, across a single high school athletic season.5–7 Moreover, high school football players may potentially sustain upwards of 1800 collisions over the course of a single season, while some studies suggest that fewer than 3000 repetitive head impacts may be associated with an elevated risk of later life impairments in executive functioning.5 8 Other studies, however, suggest that collision and contact sport participation does not necessarily result in worse neurocognitive outcomes.9–13 Furthermore, recent studies suggest that collision and contact sport athletes have fewer anxiety and depression symptoms compared with non-contact sport athletes,10 14 and they are not more likely to have depression or cognitive deficits long term.15 16 Given the lack of clarity, additional comparisons of health outcomes across the different sport types is warranted.
Investigations into the age at which an individual is first exposed to repetitive head impacts from collision/contact sport participation have yielded no significant associations with cognitive function at the collegiate level,9–11 17 18 but the influence of current sport type participation on neurocognitive performance in younger athletes warrants further study. Compared with other sport types, males make up the majority of collision sport athletes, and these athletes are likely to experience more repetitive head impacts,19 20 but the relationship between repetitive subconcussive head impacts, symptoms and cognitive functioning remains uncertain.21 22 Therefore, we investigated the association between sport type (collision, contact, non-contact), symptoms, and baseline neurocognitive test scores in a population of male high school athletes. Specifically, we sought to determine whether or not male collision sport athletes perform worse on computerised neurocognitive assessments and report greater baseline preseason symptoms than male counterparts in contact (but not collision) sports or non-contact sports. We hypothesised that there would be no meaningful differences in symptom reporting or cognitive functioning after controlling for other factors, such as attention-deficit hyperactivity disorder (ADHD) and learning problems.
Methods
Participants
We conducted a cross-sectional study of data from the Massachusetts Concussion Management Coalition. We focused on male high school student-athletes who underwent computerised neurocognitive testing using the Immediate Post-concussion Assessment and Cognitive Testing (ImPACT). Athletes in this database usually are baseline tested prior to participating in their first sport of the athletic year. If they play more than one sport they are tested prior to the first sport. For the purpose of this study, we only included each athlete’s very first baseline neurocognitive test in the database. This is a study of adolescent boys only because our intention is to complete a separate study with adolescent girls. High school boys and girls play different collision and contact sports and perform differently on the outcomes of interest, and it is important both conceptually and clinically to study them separately. All athletes completed baseline testing prior to the start of their athletic seasons between 2009 and 2018. We excluded any tests considered ‘invalid’ according to the established criteria.23 In addition, we excluded (1) those who did not take the test in English, (2) those who did not report their current sport, (3) those who participated in a sport that had fewer than 1000 participants in the dataset, (4) those who did not report their concussion history and (5) those with a self-reported history of brain surgery, treatment for epilepsy, treatment for meningitis, treatment for substance abuse or an autism diagnosis. We excluded sports with fewer than 1000 participants as those sports were less common (ie, archery, badminton, bass fishing, fencing); the 12 sports we included provide a more accurate representation of the male high school athletic population.
Participants were grouped into three categories, collision sports, contact sports and non-contact sports, based on their self-reported sport. Consistent with prior work specific to collision sports,24 we defined collision sports as those in which purposeful, body-to-body collisions occur as a legal and expected part of the game; these included football, ice hockey and lacrosse. Contact sports were defined as those during which body-to-body contact occurs as a recognised part of the sport, but purposeful body-to-body collisions are not allowed, these included baseball, basketball, soccer, and wrestling. Non-contact sports were defined as those during which body-to-body contact is a rare, unexpected occurrence; these included cross country, golf, swimming, tennis, and track and field (table 1). Our data were limited to the current sport being played because our database did not have a lifetime history of sports participation for each participant. This study was a retrospective review of deidentified data; thus, participant informed consent was not applicable. There has been no patient and public involvement in this study, as it was not appropriate for the study design.
Participant exclusion criteria
Materials
Computerised neurocognitive assessments were conducted using ImPACT, which is composed of eight specific testing modules (immediate and delayed word memory, immediate and delayed design memory, x’s and o’s, symbol match, colour match, three letters) that are used to derive composite scores (verbal memory, visual memory, visual motor speed, reaction time).25
All demographic information and comorbidities were self-reported and included a personal history of treatment for a psychiatric condition (defined as anxiety/depression), treatment for headaches, treatment for migraines, diagnosed with a learning disability (including dyslexia), diagnosed ADHD, special education, repeating one or more years of school and speech therapy (table 1).
In order to obtain this information, the participants were asked to indicate whether or not they (1) were treated for anxiety or depression; (2) were treated for headaches or migraines by a physician; (3) had ever been diagnosed with ADHD or a learning disability (including dyslexia); or (4) ever repeated one or more years of school, took special education classes or had speech therapy, all as yes/no responses. Additionally, participants were asked to report the number of times they had previously been diagnosed with a concussion. Symptoms were measured with the Post-Concussion Symptom Scale,26 a standardised questionnaire embedded in ImPACT that requires individuals to rate 22 symptoms from 0 to 6 with 0 meaning that the athlete is not experiencing the symptom, 1–2 meaning that the symptom is mild, 3–4 meaning that the symptom is moderate and 5–6 meaning the symptom is severe.27
Statistical analysis
The dependent variables were the composite scores (verbal memory, visual memory, visual motor speed, reaction time) and the total symptom score from each athlete’s first recorded baseline test. The main independent variable was sport type (collision, contact, non-contact), adjusted for age, concussion history, psychiatric diagnoses, headache, migraines, learning disability, ADHD, special education, repeating one or more years of school and speech therapy.
We used univariable one-way analyses of variance (ANOVAs) to compare demographic characteristics and composite scores between sport types. Significant ANOVAs (p<0.05) were followed up with Tukey pairwise comparisons to examine specific differences between the three sport types. We examined the proportional differences of individuals with comorbidities across each sport type using χ2 analyses. To examine the independent association between sport type and neurocognitive composite scores and total symptom scores, we conducted a series of multivariable regression models, adjusting for the potential effect of age, prior concussions,28 29 and comorbidities that previous research suggests are associated with baseline preseason symptoms and/or neurocognitive test scores, such as prior treatment for a psychiatric condition,27 ADHD,27 30 31 learning disability27 30 31 and migraines.27
Due to our large sample size and high statistical power we used effect sizes (eta-squared and partial eta-squared) to interpret clinically meaningful results with 0.01, 0.06 and 0.14 corresponding to small, medium, and large effects, respectively, for the ANOVA, and 0.02, 0.13 and 0.26 corresponding to small, medium and large effects, respectively, for the regressions.32 The p value alone informs the existence of an effect but does not reveal the size of the effect.33 Large samples, such as ours, will frequently demonstrate statistical significance with no context of the meaningfulness of the findings; thus, we felt it was necessary to include effect sizes to avoid any misinterpretation of our findings. All analyses were completing using Stata/IC V.15.1 (StataCorp).
Results
A total of 106 239 high school boys had valid baseline neurocognitive tests. We excluded 13 260 individuals based on the above exclusion criteria (table 1), leaving 92 979 male athletes included in the final analysis. Athletes were similar in age across sport type (table 2). Collision sport athletes were more likely to report prior concussions and ADHD (table 2). On univariable comparisons, collision sport athletes performed slightly but significantly worse on the neurocognitive composite scores, and collision and contact sport athletes both reported slightly but significantly lower baseline symptom scores compared with the contact and non-contact sport athletes (table 3). After adjusting for the effects of age, concussion history and comorbidities, collision and contact sport athletes still performed slightly but significantly worse on composite scores and had slightly but significantly lower symptom scores than non-contact sport athletes (table 4).
Self-reported demographics from the impact test for each sport category
Impact composite scores across the three sport types
The association between collision sports, contact sports, and shown variables using non-contact sports as a reference
Discussion
High school boys competing in collision and contact sports performed slightly worse on baseline preseason neurocognitive testing compared with boys participating in non-contact sports. Collision and contact athletes also reported slightly fewer symptoms than non-contact sport athletes. Neither of these findings is of likely clinical significance.
Previous studies of adolescent12 and collegiate10 11 athletes found no association between sport and neurocognitive test performance and no significant differences for sport type on composite scores during baseline preseason evaluations. A similar large scale investigation of male NCAA athletes undergoing preseason testing found that football players had lower (worse) visual motor processing speed and slower (worse) reaction time compared with non-contact sport athletes, however, the authors reported small effect sizes and minimal clinical relevance, similar to our study.9 Others have examined the influence of sport on cognition across an athletic season and found small but measurable short-term differences in neurocognitive outcomes between collision, contact and non-contact high school and collegiate athletes,13 although the magnitude of the differences between sport type did not reach the thresholds deemed to be clinically significant and did not persist across subsequent athletic seasons.13 Similarly, previous studies have found lower symptom scores in adolescent12 and collegiate athletes10 associated with collision sport participation. It is not known as to why collision sport athletes report fewer symptoms, but it is possibly due, at least in part, to collision sports being predominantly male, as sex has been associated with baseline symptom reporting in a number of studies.26 27 34 This would not have been a factor in our study, however, because all included athletes were boys.
Adolescent student-athletes with ADHD have a greater lifetime history of concussions35 and perform somewhat worse on computerised neurocognitive testing than those without ADHD.36 A modestly higher percentage of collision sport athletes (13%) reported ADHD compared with contact (9%) and non-contact (10%) sport athletes. This did not influence our findings, however, because we controlled for this variable in our analyses. The percentages of collision and contact sport athletes (4%) reporting a psychiatric condition (anxiety and/or depression) was similar to non-contact (5%) athletes, although previous investigations have found better quality of life outcomes in high school collision and contact sport athletes,14 and lower depression levels in collegiate football players.10
The observed differences in neurocognitive test performance and total symptom scores in our study are of questionable clinical relevance. Each of the differences in composite and symptom scores had small or very small effect sizes. Given the large number of athletes involved, even very small effects are likely to be statistically significant. The distributions of neurocognitive test scores and total symptom scores across the three groups are mostly overlapping. Moreover, the magnitudes of the differences between the groups in this study are much smaller than those observed when an uninjured athletes takes ImPACT twice.37
This study has several limitations. By design, we included only male high school athletes. We are currently performing similar analyses for female athletes. A computerised neurocognitive screening battery was used, so it is possible that a more comprehensive neuropsychological assessment may have detected stronger associations with sport type. Additionally, there were a number of individuals who had multiple baseline neurocognitive scores in the dataset, and while our analysis only included composite scores from the first assessment, we had no way of knowing how many times the participants had taken the test prior to reaching high school. It is possible that collision and contact sport athletes have a greater history of computerised neurocognitive testing due to the higher risk of concussion in their sports compared with non-contact sport athletes. Therefore, we cannot rule out the possible influence of a learning effect for some individuals. Most importantly, our athletes were grouped based on the sport type that they reported currently playing, but the scope of our database made us unable to account for prior, simultaneous or future sports participation. Thus, it is possible that (1) some individuals participated in more than one sport during the school year and (2) non-contact sport participants had a history of collision or contact sports participation. We classified soccer as a contact sport, based on prior literature,24 but the classification may warrant reconsideration in future studies, as repeated head trauma, particularly subconcussive impacts, routinely occur. We cannot speculate, based on the results of this study, on possible later in life brain health for these student athletes. There are ongoing research efforts to examine long-term brain health in former elite or professional soccer players in Europe,38 39 for example, and more research is needed regarding the later in life brain health of those who played high school sports.
High school boys playing collision and contact sports perform slightly worse and have slightly lower symptom scores on neurocognitive baseline testing than non-contact sport participants, but the differences are of unlikely clinical significance. Our findings suggest that sports type and the associated risk of subconcussive impacts do not result in clinically relevant differences in self-reported symptoms or neurocognitive functioning in current youth athletes.
Data availability statement
All data relevant to the study are included in the article or uploaded as online supplemental information.
Ethics statements
Patient consent for publication
Ethics approval
The Boston Children’s Hospital Institutional Review Board (IRB-P00030699) approved this study prior to any data analysis.
References
Footnotes
Twitter @jroldham
Contributors JRO conceptualised and designed the study, carried out the analyses, drafted the original manuscript, revised and reviewed the final manuscript, and served as the guarantor. WM and GLI assisted with study conceptualisation and design, revised and reviewed the final manuscript, and critically reviewed the manuscript for intellectual content. DH, PB and RM all contributed to the revision and review of the final manuscript and critically reviewed the manuscript for intellectual content. CL contributed to the structure and organisation of the collected data, and revised and reviewed the final manuscript. All authors approved the final manuscript as submitted and agree to be accountable for all aspects of the work.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests WM receives royalties from (1) ABC-Clio publishing for the sale of his books, Kids, Sports and Concussion: A guide for coaches and parents, and Concussions; (2) Springer International for the book Head and Neck Injuries in Young Athlete and (3) Wolters Kluwer for working as an author for UpToDate. His research is funded, in part, by philanthropic support from the National Hockey League Alumni Association through the Corey C. Griffin Pro-Am Tournament and the National Football League. DH receives research support from the Eunice Kennedy Shriver National Institute of Child Health and Human Development (R03HD094560) and the National Institute of Neurological Disorders And Stroke (R01NS100952 and R41NS103698) of the National Institutes of Health. He has previously received research support from a research contract between Boston Children’s Hospital, Cincinnati Children’s Hospital Medical Center and ElMindA, and the Eastern Athletic Trainers Association. GLI serves as a scientific advisor for NanoDx(formerly BioDirection), Sway Operations, and Highmark. He has a clinical and consulting practice in forensic neuropsychology, including expert testimony, involving individuals who have sustained mild TBIs (including athletes). He has received research funding from several test publishing companies, including ImPACT Applications, CNS Vital Signs and Psychological Assessment Resources (PAR). He has received research funding as a principal investigator from the National Football League, and salary support as a collaborator from the Harvard Integrated Program to Protect and Improve the Health of National Football League Players Association Members. GLI acknowledges unrestricted philanthropic support was provided by the National Rugby League, ImPACT Applications, the Mooney-Reed Charitable Foundation, the Boston Bolts, and the Spaulding Research Institute. Those entities were not involved in the study design, collection, analysis, interpretation of data, the writing of this article or the decision to submit it for publication.
Provenance and peer review Not commissioned; externally peer reviewed.