https://orcid.org/0000-0001-5294-3332
ABSTRACT
Objective: To assess the 52-week incidence proportion and incidence rate of sports-related concussion (SRC) among elite Para athletes, and to analyze the injury mechanisms.
Method: In total, 70 male and 37 female Swedish elite Para athletes (median age 29 years) with vision, physical and intellectual impairment, weekly self-reported sports-related injuries including concussion in an eHealth application adapted to Para athletes. Descriptive statistics were used to assess the incidence rate and incidence proportion. Chi-square statistics were used to analyze differences in the proportion of SRC.
Results: A total of 13 SRC were reported: three athletes each sustained two SRC. The incidence proportion was 9.3% (95% CI 4.8–16.7), and the incidence rate 0.5 SRC/1000 hours (95% CI 0.3–0.9) of sports exposure. Athletes with vision impairment and female athletes reported a significantly higher proportion of SRC. A majority of the injuries (n = 9; 69%) occurred during sport-specific training. The injury mechanisms were collision with object (n = 7; 54%), collision with person (n = 4; 31%), and poor playing field conditions (n = 2; 16%).
Conclusion: The incidence of concussion among elite Paralympic athletes is comparable to sports for able-bodied athletes. Athletes with vision impairment and female athletes reported a significantly higher incidence of SRC, and collisions were the most common injury mechanism. These results can form the basis for future preventive research studies.
Introduction
Sports-related concussion (SRC) is receiving increased recognition world-wide. Over the past decade, several research studies, reviews and consensus statements have been published focusing on concussion recognition, injury mechanisms, assessment, acute and long-term management, and prevention (Citation1–5).
Concussion among Para athletes – the International Paralympic Committee’s (IPC) term for a sportsperson with a physical, vision, or intellectual impairment – has not until recently received similar attention. Para athletes’ performances are steadily improving, and their skills, speed, and impact have increased (Citation6). This has led to an increased awareness of sports injuries and illnesses in Para sport, and in particular concussions (Citation7,Citation8). Several Para sports, such as alpine skiing, para ice hockey, para equestrian, judo, wheelchair rugby, wheelchair basketball, athletics, football-5-a-side and 7-a-side, expose the athlete to the risk of sustaining a SRC (Citation9). In addition to the well-known sport-specific risk factors (high speeds, falls and collisions), Para athletes have intrinsic risk factors related to their impairment, such as impaired vision, paralysis, poor balance and impaired executive function, that make them more susceptible to SRC (Citation9). Extrinsic risk factors, such as the use of assistive devices, wheelchair strapping and dependency on a guide, could also make them sustain a SRC more easily.
Taken together, Para athletes may be more likely to sustain an SRC compared to able-bodied athletes (Citation10). Yet, our knowledge of the epidemiology of concussion in Para sport is almost non-existing. To move toward a better understanding of the extent, mechanisms, risk factors and preventive measures, there is a need for epidemiological studies assessing the burden and risk factors of SRC among Para athletes. Moreover, such studies should cover both training and competition.
The aims of this study were to prospectively assess the 1-year incidence proportion and incidence rate of SRC among elite Para athletes, and to analyze the injury mechanisms of their SRC.
Material and methods
Study design
This study is part of the “Sports-Related Injuries and Illness in Paralympic Sport Study” (SRIIPSS) (Citation11), a prospective longitudinal cohort study that weekly collected data from January to December 2017 (i.e., 52 weeks) on self-reported sports-related injuries and illnesses among Swedish elite Para athletes. SRIIPSS followed the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines and was registered at ClinicalTrials.gov [NCT02788500].
In SRIIPSS, an eHealth application, specifically developed for Para athletes with various impairments, was used for the data collection (Citation12). Subsequently, data from 107 Swedish elite Para athletes were weekly collected during 52 weeks. The overall prevalence (Citation13) and incidence (Citation14) of injuries and illness have previously been described and further details can be found therein.
In the present study, data specifically on SRC, collected as part of SRIIPSS, were used and analyzed.
Ethical considerations
The study followed the WMA Declaration of Helsinki Ethical Principles for Medical Research Involving Human Subjects and was approved by the Regional Ethical Review Board in Lund, Sweden (Dnr 169/2016). Participation was voluntary and informed consent was obtained from all participants.
Study population
Participants were recruited through the Swedish Paralympic Program, which at the time of the study (year 2017) included all candidates (N = 150) for the Summer and Winter Paralympic Games. The following inclusion criteria were used: i) age 18–65 years; ii) being able to communicate in Swedish; and iii) having the ability to respond electronically to the eHealth application.
Before the start of SRIIPSS, the following data were collected from the participants: (i) athlete demographics (sex, age); and (ii) impairment characteristics (type of impairment, sports classification, use of assistive device). The athletes were firstly categorized according to their overall impairment: physical, vision, or intellectual. Thereafter, the athletes were categorized into subgroups in agreement with epidemiological research conducted within the International Paralympic Committee: vision impairment, intellectual impairment, limb deficiency, spinal cord injury, central neurological impairment and les autres (e.g., muscular dystrophy, multiple sclerosis, post-polio syndrome). We also categorized the athletes based on their main mode of transportation in daily activities (using a wheelchair or being ambulatory).
Data collection
In SRIIPSS, the athletes received every week during 52 weeks a web survey through e-mail and/or text message with questions regarding their previous training week (Citation12). Athletes that reported a new injury were asked about body location, injury type and mechanism, involvement of their impairment and diagnosis. Exposure was reported as the number of training minutes. Data were followed-up every week and when the athlete reported being back in normal training and/or sports participation, a closure form was sent with additional open-ended questions regarding type of injury, contact with medical personnel, time loss from sport, if the impairment was involved in the injury mechanism and preventive possibilities (Citation14).
In the present study, an SRC was recorded: (i) if the athlete had a blow to or jolting of the head that had caused an acute disruption of brain function with concomittant symptoms; (ii) if it had caused changes in normal training or competition regarding the mode, duration, intensity, or frequency; and (iii) if it was confirmed by medical personnel. The SRC was further categorized by the number of days until the athlete returned to normal training and sport participation: 1–3 days, 4–7 days, 8–20 days, ≥21 days, and ≥3 months.
For each athlete, their sport characteristics (i.e., type of sport, hours per week engaged in training and competition and training load) were also recorded. A total training load rank index (TLRI) was calculated by multiplying the weekly rate of perceived exertion (RPE) with minutes of sports participation; the TLRI was then categorized into low, middle, or high, based on the 33rd and 67th percentiles. The use of TLRI for Para athletes has been described in our previous study protocol (Citation11) and validated in our pilot feasibility study (Citation12).
Data analysis
To determine the proportion of athletes that sustained an SRC, the incidence proportion was calculated by dividing the number of athletes with an SRC by the total number of athletes. To assess the total burden of SRC, the incidence rate of SRC was calculated based on 1000 hours of sports exposure (Citation15); this is the established method when reporting injury incidence and thereby enabled us to compare with previous studies. To compare any differences between the athlete categories for the proportion of SRC, pair-wise comparisons were conducted using Pearson chi-square statistics for homogeneity. In cases where more than 20% of expected frequencies were less than five, Fisher’s exact test was used. Calculation of Cramer’s Phi was used to measure the effect size. A 95% confidence intervall (CI) and a p-value of <0.05 were used to assess the data. All calculations were made with IBM SPSS Version 25.
Results
Athlete demographics
A total of 107 athletes were enrolled in SRIIPSS () and provided weekly data about any sports-related injuries, illnesses, and other health variables for 52 weeks. The weekly response rate was 72%, and the median number of completed weekly reports per athlete throughout the 52 weeks was 45 (IQR 25–52, min-max 1–52). The mean time of weekly sports exposure was 6.8 ± 4.8 hours. The median age of the athletes was 29 (IQR 23–36).
Figure 1. Flowchart describing the Swedish elite Para athletes (n = 107) included in The Sports-related Injury and Illness in Paralympic Sport Study (SRIIPSS)
Incidence proportion and incidence rate of SRC
A total of 13 SRC were reported during the 52 weeks; all were confirmed by a physician or sports physiotherapist. The 13 SRCs were reported by 10 different athletes; three athletes reported that they each had sustained two SRCs. This yielded an incidence proportion of 9.3% (95% CI 4.8–16.7). The total burden of SRC, i.e. incidence rate, was 0.5 SRC/1000 hours (95% CI 0.3–0.9) of sports exposure.
Female athletes reported a significantly higher incidence rate of SRC (0.80; 95% CI 0.5–1.4) (p = .04) compared to male athletes (). Athletes with a vision impairment reported a significantly higher incidence proportion of SRC (27.3% (95% CI; 12.6–48.7) (p = .01) and a significantly higher incidence rate of SRC (1.24; 95% CI 0.5–2.99) (p = .01) than athletes in the other impairment groups (). There were no significant relations regarding sport (summer vs winter and team vs individual), training load (low, middle, high) or between athletes using a wheelchair or being ambulatory.
Table 1. Incidence proportion and incidence rate of sports-related concussion (SRC) during 52 weeks among Swedish Para athletes (n = 107)
Injury mechanisms of SRC
Almost two-thirds (62%) of the SRC occurred among athletes participating in a blind sport (i.e., sport for people with a vision impairment who are blind or partially sighted). Four (31%) of the SRC occurred in goalball (participants compete in teams of three and try to throw a ball with bells inside into the goal of the other team), two (15%) in para swimming and two (15%) in judo. The remaining SRC were reported in the following sports: para equestrian (n = 2; 15%), para ice hockey (n = 2; 15%) and wheelchair basketball (n = 1; 8%). A majority (n = 9; 69%) of the SRC occurred during sport-specific training and the remaining (n = 4; 31%) during competition.
The injury mechanism was related to a collision in eleven (85%) of the SRC; seven of the injuries were a collision with an object and four with another person. All of the SRC among athletes with vision impairment were related to a collision. The two remaining injuries were related to surface/weather or not following the rules.
The athletes reported that their impairment influenced the injury mechanism in five (38%) of the SRC. Injury mechanisms influenced by the impairment were reported to be related to poor balance in para equestrian (due to a neurological disease), and by athletes with a vision impairment and use of blindfolds in goalball, swimming into the wall in para swimming and being thrown in an unexpected direction in judo.
Five of the SRC (38%) lead to a time loss from participation in normal training and sport for more than 21 days. Four (31%) lead to a time loss for 8–20 days, and the remaining four SRC (n = 4; 31%) lead to a time loss for 4–7 days.
The athletes reported that six (46%) of the SRC could have been prevented. Athletes with vision impairment reported that more guides, tappers (in swimming) and better knowledge and awareness among coaches could possibly have prevented their SRC.
Discussion
The results from this 52-week prospective study revealed that 9.3% of the elite Para athletes reported at least one SRC during 1 year. The incidence rate was 0.5 SRC per 1000 hours of sports exposure. Athletes with a vision impairment and female athletes reported significantly more SRC compared to other athlete categories.
The burden of SRC in para sport
To the best of our knowledge, this is the first study that has prospectively reported the burden of SRC in Para sport over a longer period of time, and during both training and competition.
When comparing the results to the few other prospective studies within the field of elite Para sport, a relatively lower burden has been reported. In a study from the pre-competition and competition periods of the 2012 summer Paralympic Games in London, UK, a total of 12 head injuries were reported among 3565 athletes (Citation16). During the 2016 summer Paralympic Games in Rio de Janeiro, Brazil, a total of seven head injuries were reported among 3657 athletes, resulting in an incidence proportion of 0.2% (Citation17). During the winter Paralympic Games, a higher burden of head injuries was reported. A total of 31 injuries were recorded among 26 athletes in the anatomical areas of the head, face and neck during the 2014 winter Paralympic Games 2014 in Sochi, Russia; with 547 athletes participating in this winter Paralympic Games this resulted in an incidence proportion of 4.8% (Citation18). In the 2018 winter Paralympic games in PyeongChang, South Korea, a total of 29 injuries were reported in the head, face and neck among 27 athletes, with an incidence proportion of head and neck injuries of 4.8% (Citation19). A majority of these injuries (78.9%) did not lead to any time loss from sport, whereas six of the injuries (20.7%) were classified as moderately serious to serious (Citation19). It should be noted that during the Paralympic Games, athletes could actually be training and competing less than during a normal season. Therefore, these values may not be fully comparable to our data, which covers a whole year and both training and competition.
Furthermore, the authors of the studies from the Paralympic Games concluded that several incidents with athletes who suffered a blow to the head followed by unsteady gait were noticed but not recorded. It was therefore suggested that SRC may be under-reported in this athlete population. One study surveyed athletes that participated in wheelchair basketball (Citation20). In their sample of 263 players, 6.1% reported a concussion within the current season, and as many as 44% who experienced a concussion did not report it. Reasons were that they did not think the injury was serious enough and that they did not know if it was a concussion (Citation20). Therefore, it has been suggested that there is a need to engage clinicians and coaches in education regarding SRC recognition, assessment and management in Para sport (Citation9).
When comparing the results from the present study with similar studies among able-bodied athletes, comparable number of SRC have been reported. In a systematic review of SRC in sports over an entire season, the incidence rates were 0.1–1.12/1000 hours of exposure in football, 0.52–1.60/1000 hours of exposure in rugby and 3.07/1000 hours of exposure in ice hockey (Citation5). A similar study of elite collegiate players have reported an incidence proportion of 7% in elite basketball and 7–11% in football (Citation21). Among able-bodied athletes it has been reported that the rate of SRC is higher during competition compared to training (Citation22). In the present study the majority of the SRC occurred during training and it is recommended to further evaluate whether Paralympic athletes have a higher risk of SRC during training compared to able-bodied athletes. Data on unreported concussion among able-bodied athletes are scarce, and similar to Para sport there is a need to develop reliable means by which an SRC can adequately reported.
Associations and injury mechanisms
In the present study, Para athletes with a vision impairment reported a significantly higher incidence proportion and incidence rate of SRC compared to athletes with other impairments. This is the first study that specifically has evaluated the incidence of SRC among Para athletes with different impairments, and there are therefore no comparable data.
Noteworthy is that all SRC among athletes with a vision impairment in the present study were related to a collision. Collisions in blind sports have been described to be a problem (Citation16). SRC among athletes with a vision impairment should therefore be considered a special concern, as many of them have reported to have symptoms, such as headache, concentration deficits, depressive disorders and chronic fatigue syndrome, because of their vision impairment (Citation23). Many of these symptoms may also arise after an SRC, which possibly may increase and worsen the situation for athletes with a vision impairment. To reduce the burden of SRC among athletes with a vision impairment, it can be recommended to further evaluate the injury mechanism, to assure appropriate guidance and to inform athletes, coaches, and referees about the increased risk of SRC. This further emphasizes the need to continue the development of preventive measures in order to reduce the impact of SRC in Para sport.
Also, female athletes had a significantly higher incidence rate of SRC compared to male athletes. This was observed in the study of wheelchair basketball players (Citation20) and has been reported among able-bodied athletes (Citation1,Citation24). In a meta-analysis (Citation5), it was shown that female athletes in football and ice hockey had a higher incidence density of SRC compared to male athletes. It has been discussed that factors such as differences in neck strength, different playing styles and willingness to report injuries may contribute to the higher incidence rates (Citation1). There is, however, still a paucity in the sports medicine literature concerning SRC among both female able-bodied athletes and female Paralympic athletes, and it is recommended to further evaluate the epidemiology of SRC among female athletes.
In the present study, three athletes reported two SRC each during the 52-week data collection period. Among able-bodied athletes, a previous SRC is a major risk factor for a subsequent concussion (Citation1,Citation25). This is of special concern, as a subsequent SRC may exacerbate the symptoms and lead to very long-term consequences, such as chronic traumatic encephalopathy (Citation26). It is therefore recommended to focus future research on preventing the primary SRC, but also to target Para athletes that already have sustained an SRC in order to minimize the risk for a subsequent injury and the possibility of second impact syndrome.
Strengths, limitations, and future research
A strength of the present study is that SRC were recorded prospectively based on sports exposure and both during training and competition periods, and that elite Para athletes with various impairments (physical, vision, and intellectual) participated. A limitation is that the SRC were self-reported and data from, for example, the Sport Concussion Assessment Tool (SCAT5) (Citation27) were not included. However, all SRC were confirmed by medical personnel, which was important for the validation. As Para athletes is a heterogeneous and understudied population with limited resources related to medical support, we believe that self-reports are feasible (Citation14). Self-reports of symptoms are also used in the current clinical guidelines concerning return to play following an SRC in able-bodied athletes (Citation3). Future studies should, however, consider alternative data collection methods to broaden our knowledge in this area.
Another limitation of the present study is that few athletes from the high-risk winter sports and none from football-5-side were included. Thus, the burden of SRC may be even greater when these sports are included. Furthermore, SRC are commonly underreported due to lack of knowledge concerning symptoms and consequences, and athletes’ tendency to avoid reporting symptoms following a SRC (Citation1,Citation9,Citation20). It has therefore been suggested that education of athletes, coaches, and sports organizations should play a major role in the assessment and prevention of SRC in Para sport (Citation28,Citation29). Even though we included over 100 Para athletes, a larger sample size would have enabled us to make more detailed inferences. As athletes from only one country participated, further studies across nations are needed to corroborate these results. Given the limited knowledge in this field, larger prospective studies over time are therefore warranted.
To increase knowledge, awareness, and research on SRC among Para athletes, the Concussion in Para Sport (CIPS) Group was formed 2020. The group has produced the First Position Statement (Citation30), which emphasizes that clinicians working with Para athletes must fully understand and appreciate the limitations when applying existing concussion consensus guidance. Furthermore, it is emphasized that research relating to all aspects of concussion in Para athletes is needed together with concussion education and awareness for clinicians, coaches, and athletes. This will eventually improve the safety and welfare of all athletes and staff.
Conclusion
This is the first study that prospectively has reported the incidence of SRC among elite Para athletes over time, and both during training and competition periods. The incidence rate is comparable to able-bodied athletes, indicating that SRC is a concern also in Para sport. A higher injury burden was reported compared to the Paralympic Games, indicating that elite Para athletes are exposed to a noticeable risk of SRC during their training time. Athletes with vision impairment reported a significantly higher incidence rate, and collisions were the most common injury mechanism among this athlete population. Also, female Para athletes reported a significantly higher incidence compared to male Para athletes. Future research should explore if preventive measures, targeted toward Para athletes, coaches, and officials will lead to a reduction in SRC.
Trial registration
The study is registered at ClinicalTrials.gov (Identifier: NCT02788500, registration date: 22 May 2016).
Disclosure Statement
The authors report no conflict of interest.
Data availability statement:
All data are archived according to the Swedish Act concerning Ethical Review of Research Involving Humans to attain confidentiality. Data are available from the corresponding author upon reasonable request.
Additional information
Funding
References
- Abrahams S, Fie SM, Patricios J, Posthumus M, September AV.Risk factors for sports concussion: an evidence-based systematic review. Br J Sports Med. 2014;48(2):91–97.doi:10.1136/bjsports-2013-092734.
- Barth JT, Broshek DK.Brain injury special edition on sports concussion. Brain Inj. 2015;29(2):127–28.doi:10.3109/02699052.2014.977350.
- McCrory P, Meeuwisse W, Dvorak J, Aubry M, Bailes J, Broglio S, Cantu RC, Cassidy D, Echemendia RJ, Castellani RJ, et al. Consensus statement on concussion in sport-the 5th international conference on concussion in sport held in Berlin, October 2016. Br J Sports Med. 2017;51(11):838–47.doi:10.1136/bjsports-2017-097699.
- Sports concussions. A complete guide to recovery and management. Gagnon I, Ptito A, Eds.. Boca Raton: CRC Press; 2017.
- Prien A, Grafe A, Rossler R, Junge A, Verhagen E.Epidemiology of head injuries focusing on concussions in team contact sports: a systematic review. Sports Med. 2018;48(4):953–69.doi:10.1007/s40279-017-0854-4.
- Vanlandewijck YC, Thompson WR. Training and coaching the Paralympic Athlete. Chichester, West Sussex, UK: John Wiley & Sons, Ltd; 2016.
- West LR, Griffin S, Weiler R, Ahmed OH.Management of concussion in disability sport: a different ball game. Br J Sports Med. 2017;51(14):1050–51.doi:10.1136/bjsports-2016-096767.
- Webborn N, Blauwet CA, Derman W, Idrisova G, Lexell J, Stomphorst J, Tuakli-Wosornu YA, Kissick J.Heads up on concussion in para sport. Br J Sports Med. 2018;52(18):1157–58.doi:10.1136/bjsports-2016-097236.
- Kissick J, Webborn N.Concussion in para sport. Phys Med Rehabil Clin N Am. 2018;29(2):299–311.doi:10.1016/j.pmr.2018.01.002.
- Fagher K, Lexell J.Sports-related injuries in athletes with disabilities. Scand J Med Sci Sports. 2014;24(5):E320–E331.doi:10.1111/sms.12175.
- Fagher K, Jacobsson J, Timpka T, Ö D, Lexell J.The Sports-Related Injuries and Illnesses in Paralympic Sport Study (SRIIPSS): a study protocol for a prospective longitudinal study. BMC Sports Sci Med Rehabil. 2016;8(1):28.doi:10.1186/s13102-016-0053-x.
- Fagher K, Jacobsson J, Ö D, Timpka T, Lexell J.An eHealth application of self-reported sports-related injuries and illnesses in paralympic sport: pilot feasibility and usability study. JMIR Hum Factors. 2017;4(4):e30.doi:10.2196/humanfactors.8117.
- Fagher K, Ö D, Jacobsson J, Timpka T, Lexell J.Prevalence of sports-related injuries and illnesses in paralympic Athletes. PM&R. 2020;12(3):271–80.doi:10.1002/pmrj.12211.
- Fagher K, Ö D, Jacobsson J, Timpka T, Lexell J.Injuries and illnesses in Swedish Paralympic atheletes – a 52-week prospective study of incidence and risk factors. Scand J Med Sci Sports. 2020;30(8):1457–70.doi:10.1111/sms.13687.
- Rothman K. Epidemiology: an Introduction. 2nd ed. New York: Oxford University Press; 2012.
- Willick SE, Webborn N, Emery C, Blauwet CA, Pit-Grosheide P, Stomphorst J, Van de Vliet P, Patino Marques NA, Martinez-Ferrer JO, Jordaan E, et al. The epidemiology of injuries at the London 2012 Paralympic Games. Br J Sports Med. 2013;47(7):426–32.doi:10.1136/bjsports-2013-092374.
- Derman W, Runciman P, Schwellnus M, Jordaan E, Blauwet C, Webborn N, Lexell J, van de Vliet P, Tuakli-Wosornu Y, Kissick J, et al. High precompetition injury rate dominates the injury profile at the rio 2016 summer Paralympic Games: a prospective cohort study of 51 198 athlete days. Br J Sports Med. 2018;52(1):24–31.doi:10.1136/bjsports-2017-098039.
- Derman W, Schwellnus MP, Jordaan E, Runciman P, Van de Vliet P, Blauwet C, Webborn N, Willick S, Stomphorst J.High incidence of injury at the sochi 2014 winter Paralympic Games: a prospective cohort study of 6564 athlete days. Br J Sports Med. 2016;50(17):1069–74.doi:10.1136/bjsports-2016-096214.
- Derman W, Runciman P, Jordaan E, Schwellnus M, Blauwet C, Webborn N, Lexell J, van de Vliet P, Kissick J, Stomphorst J, et al. High incidence of injuries at the Pyeongchang 2018 Paralympic Winter Games: a prospective cohort study of 6804 athlete days. Br J Sports Med. 2019;53(17):1099–104.doi:10.1136/bjsports-2018-100096.
- Wessels KK, Broglio SP, Sosnoff JJ.Concussions in wheelchair basketball. Arch Phys Med Rehabil. 2012;93(2):275–78.doi:10.1016/j.apmr.2011.09.009.
- Noble JM, Hesdorffer DC.Sport-related concussions: a review of epidemiology, challenges in diagnosis, and potential risk factors. Neuropsychol Review. 2013;23(4):273–84.doi:10.1007/s11065-013-9239-0.
- Zuckerman SL, Kerr ZY, Yengo-Kahn A, Wasserman E, Covassin T, Solomon GS.Epidemiology of Sports-Related Concussion in NCAA Athletes From 2009-2010 to 2013-2014: incidence, Recurrence, and Mechanisms. Am J Sports Med. 2015;43(11):2654–62.doi:10.1177/0363546515599634.
- Langelaan M, De Boer MR, van Nispen RM, Wouters B, Moll AC, van Rens GH.Impact of visual impairment on quality of life: a comparison with quality of life in the general population and with other chronic conditions. Ophthalmic Epidemiol. 2007;14(3):119–26.doi:10.1080/09286580601139212.
- Cheng J, Ammerman B, Santiago K, Jivanelli B, Lin E, Casey E, Ling D.Sex-Based Differences in the Incidence of Sports-Related Concussion: systematic Review and Meta-analysis. Sports Health. 2019;11(6):486–91.doi:10.1177/1941738119877186.
- Nordström A, Nordström P, Ekstrand J.Sports-related concussion increases the risk of subsequent injury by about 50% in elite male football players. Br J Sports Med. 2014;48(19):1447–50.doi:10.1136/bjsports-2013-093406.
- Stern RA, Riley DO, Daneshvar DH, Nowinski CJ, Cantu RC, McKee AC.Long-term consequences of repetitive brain trauma: chronic traumatic encephalopathy. PM&R. 2011;3(10 Suppl 2):S460–7.doi:10.1016/j.pmrj.2011.08.008.
- Echemendia RJ, Meeuwisse W, McCrory P, Davis GA, Putukian M, Leddy J, Makdissi M, Sullivan SJ, Broglio SP, Raftery M.The Concussion Recognition Tool 5th Edition (CRT5): background and rationale. Br J Sports Med. 2017;51(11):870–71.doi:10.1136/bjsports-2017-097508.
- Register-Mihalik J, Baugh C, Kroshus E, Y Kerr Z, Tc VM.A multifactorial approach to sport-related concussion prevention and education: application of the socioecological framework. J Athl Train. 2017;52(3):195–205.doi:10.4085/1062-6050-51.12.02.
- Griffin S, West LR, Ahmed OH, Weiler R.Concussion knowledge, attitudes and beliefs amongst sports medicine personnel at the 2015 Cerebral Palsy Football World Championships. Br J Sports Med. 2017;51(4):325–325.doi:10.1136/bjsports-2016-097372.106.
- Weiler R, Blauwet C, Clarke D, Dalton K, Derman W, Fagher K, Gouttebarge V, Kissick J, Lee K, Lexell J, et al. Concussion in para sport: the first position statement of the Concussion in Para Sport CIPS) group. Br J Sports Med. 2021;1–9.