https://orcid.org/0000-0001-5800-7000
ABSTRACT
Aim
To describe trends in the incidence of match concussions and time to return-to-play in professional rugby union.
Methods
Match concussion incidence (injuries per 1000 player-match-hours) and time to return-to-play (mean and median days absence) were recorded in 3006 male professional rugby union players over 16 seasons (2002/03 – 2018/19).
Results
From 2002/03 to 2009/10, incidence of concussions was stable at 4.3/1000 player-match-hours. From 2009/10 to 2018/19, there was an increase in concussion incidence, with the highest incidence in 2016/17 at 20.9/1000 player-match-hours (95% CI: 17.9–24.3). Annual prevalence of concussion also increased, suggesting more players were concussed rather than the same players sustaining more concussions. Before the introduction of standardized graduated return-to-play (GRTP) guidelines in 2011, 27% of players returned to play in <6 days. After the introduction of the GRTP, this decreased to 7%, with no players returning in <6 days after 2014/15. Between 2002/03 and 2018/19, incidence of all other injuries remained stable.
Conclusions
From 2009/10 onwards, the incidence of diagnosed concussions increased. Since the introduction of the GRTP, there has been a dramatic reduction in the number of players returning in <6 days.
INTRODUCTION
Rugby union is a full-contact sport, with around 450 contact events per professional match (Citation1). Many of these events can involve head contact and, as a consequence, there is a high incidence of concussion in professional rugby union. Kemp et al. (Citation2), reported that 8% of professional players sustained at least one concussion per season (2002/03, 2003/04 and 2005/06), with an incidence of match concussions of 4.1/1000 player hours. Between 2007/08-2010/11, the incidence of match concussions in the same professional league was similar [4.6/1000 player hours (Citation3)]. However, in this and other professional leagues an increase in concussion incidence has been reported since this time (Citation4,Citation5).
In recent years, there has been an evolution in the management of concussion in rugby. In 2011, professional rugby in England, following a change in World Rugby regulation and concussion guidelines, introduced the standardized six-stage graduated return-to-play (GRTP) guidelines, with each stage lasting a minimum of 24 hours and the final stage being a return to game play, meaning that the minimum return-to-play time is 6 days. Prior to the introduction of this guideline, World Rugby Regulation 10 stipulated a 3-week stand-down from training and playing unless cleared by neurological specialist (in this event there was effectively no defined lower time limit to return). The introduction of the GRTP was aligned with the recommendations from the 4th International Consensus Statement on Concussion in Sport in 2011 (Citation6). In 2012, a standardized off-field multimodal assessment protocol with a temporary substitution was introduced in professional rugby globally (now named the Head Injury Assessment (HIA) (Citation7)). This significantly reduced the number of players that continued to play but were subsequently diagnosed to have sustained a concussion (Citation7). In the 2014/15 season, mandatory annual concussion education was introduced for all players, coaches, medical staff and game officials engaged in professional rugby in England (Citation8). In 2016, real-time video monitoring and review of head impacts with the potential to result in concussion was introduced to aid the recognition and diagnosis during match play (Citation9). In addition to these initiatives, there has been a substantial increase in media attention during this period, particularly around the potential long-term effects of concussion on neurological function (Citation10).
The aim of this study was to explore how the incidence, annual prevalence and return-to-play from match concussions changed in professional rugby union in England over the period 2002 to 2019 with a particular focus on the impact of evolving concussion identification, management and education strategies in relation to this complex brain injury in the sport.
MATERIAL AND METHODS
Participants
This prospective cohort study included data collected from a total of 3006 unique male professional rugby union players (9213 player-seasons) over a 16 season period of the English Premiership between 2002 and 2019 (no data were collected in the 2004/05 season). Data for the periods 2002 to 2006 (Citation2) and 2007 to 2011 (Citation3) and the full study period (Citation5) have been published previously (the latter with a focus on all match injuries). This study focuses exclusively on injuries diagnosed as concussions and elaborates on some of the key changes over the period which may have contributed to the changes seen in the rates and severity of this injury type. In 2002/03 and 2003/04, one club did not take part in data collection, but from 2005/06 onwards, all 12 clubs participating in the Premiership each season (16 unique clubs over the period) were required to participate in the study as part of the competition agreement. Staff at clubs recorded injury data in alignment with competition requirements and medical standards, informed by the 2007 rugby consensus statement for data collection procedures for studies of injuries in rugby union (Citation11). Players were included if they were a member of the first team squad and had provided written informed consent. The study was approved by the research ethics committee of the academic host institution where the project was based for each season (the Universities of Leicester, Nottingham and Bath) and player consent was obtained every season regardless of whether the player had consented to the project previously.
Procedures
A 24-hour time-loss definition of injury was used throughout the study as per the 2007 consensus statement (Citation11). Club medical personnel reported all match and training injuries on a weekly basis, with all included concussions diagnosed on clinical grounds by team physicians with specific regular training in this area. Staff completed a standard injury report form on paper (2002/03-2012/13) or electronically (2013/14-2018/19) that detailed the injury diagnosis using the Orchard Sports Injury Classification System [OSICS (Citation12)], using a 3-digit code prior to 2012, and a 4-digit code thereafter. To calculate match exposure per team, the number of matches was multiplied by the number of players exposed (fifteen) by the time exposed in hours [1.33 (Citation11)]). Throughout this study, Rugby Football Union guidance was given to club medical staff that match-related concussion should be suspected on the basis of the on-field presentation of one or more of the typical symptoms, physical signs, or cognitive features described in the 2001 concussion in sport summary and agreement statement (Citation13), and the subsequent 2004 (Citation14), 2008 (Citation15), 2012 (Citation6) and 2016 (Citation16) concussion consensus statements, after a blow to the head or body during a match. All concussions (including for players who were immediately removed from play following on-pitch assessment) were the result of post-match diagnosis and clinical confirmation by a team physician. The on-pitch recognition of concussion evolved with the Concussion in Sport consensus statements over the period of the study. For the 2002/03-2010/11 seasons, World Rugby Regulation 10 stipulated a 3-week minimum stand down period from playing and training following a concussion (unless cleared by a neurological specialist) for all players. In the event of clearance by a neurological specialist there was no minimum stand-down. From 2011/12 onwards, clubs were advised to manage players according to the graduated return-to-play (GRTP) protocol set out by World Rugby (Citation17). This step-wise return-to-play protocol should result in a minimum return-to-play time of 6 days from the day of concussion.
Injury severity was defined as the number of days absent from full training or match play (Citation11). Injury burden was calculated as the mean incidence multiplied by the mean severity and reported as the mean number of days lost per 1000 hours (Citation18). All match and training concussions were recorded prospectively, but as 95% of reported concussions during the study period occurred during match play, this study focuses on match concussions only. Match concussions were included in the study if they occurred in 1st team Premiership or National and European Cup competitions. Match concussions that occurred in pre-season, non-league matches, and those matches classified by club staff as 2nd team were not included as player exposure for these matches was not captured over the period 2002–2012.
Data Analysis
Match injury incidence (for concussion and all injuries) is reported as the number of injuries per 1000 player-match-hours, with 95% confidence intervals (95% CI). Injury severity is reported as both mean and median days absence from training and/or match play. Season prevalence is reported as the percentage of players in any given season who reported at least one concussion. Data were aggregated for the period before and after the introduction of the HIA (2002–2011 and 2012–2019) as well as before and after the introduction of the GRTP (2002–2012 and 2013–2019). Linear regression was used to identify trends over time, with significance set at p ≤ 0.05. Beta coefficients for each regression model were reported as the yearly change in each respective outcome variable (e.g. incidence, severity). To account for the multiple tests being undertaken, p-values were adjusted using the false discovery method (Citation19). All analysis was undertaken using IBM SPSS Statistics for Apple (Version 24.0.0).
RESULTS
Between 2002 and 2019, 124952 player-match-hours were recorded. There were 10851 time-loss match injuries of any type, of which 1145 were medically diagnosed match concussions (10.6% of all injuries). Of the 3006 players included in this study (a total of 9213 player-seasons), 76% did not report a concussion at any time, making the overall 16-season period prevalence of concussion 24% (734 players). Fifteen percent of all players had one concussion, 5% had two concussions, 2% had three concussions and 2% had four or more concussions. The highest number of concussions diagnosed for any player was eight over five seasons. The season prevalence of concussion ranged from 4% to 20% and increased from 5.6% per season prior to the introduction of the HIA to 14.4% after its introduction (). The proportion of all injuries which were concussion changed over the study period, with concussion accounting for a low of 3.7% of all injuries in the 2003/04 season and a high of 25.3 during the 2015/16 season (). The proportion of concussions did not change substantially from month-to-month within seasons ().
Table 1. Incidence, prevalence, severity and burden of concussions from 2002/03 to 2018/19
The Incidence of Concussion (and other injuries)
The incidence of concussion demonstrated considerable yearly variation between 2002 and 2019. Annual values ranged from the lowest incidence in 2005/06 [3.1/1000 hours (95% CI: 2.0–4.8)] to 20.9/1000 hours (95% CI: 17.9–24.3) in 2016/17. Descriptively, the data can be divided into three phases: the 2002/03 season to the 2009/10 season had a stable concussion incidence, between 2009/10 and the 2016/17 season the incidence increased every year and from the 2016/17 season onwards, concussion incidence stabilized again, albeit at a much higher level than previously ( and ). Over the whole study period, there was a significant rise in the incidence of concussion (B = 1.2, p < .01, 95% CIs: 0.8–1.6) indicating a yearly rise in the incidence of 1/1000 hours; however, the increase was principally driven by the increase from 2009 to 2016/17 (B = 2.4, p < .01, 95% CIs: 1.8–3.1) indicating a yearly rise of 2/1000 hours over this period. Prior to the introduction of the HIA protocol in the 2012/13 season, mean incidence was 4.4/1000 hours (95%CIs: 3.7–5.0), while after its introduction, the mean rate was 15.1/1000 hours (95%CIs: 10.2–19.9: ). For the period 2002–2011, concussion was the 4th most commonly diagnosed match injury. However, in each season from 2011/12 to 2018/19, concussion was the most commonly diagnosed match injury.
Figure 1. The incidence (per 1000 player-match-hours) of a: all time-loss match injuries (dashed line), b: contact match event injuries excluding concussion (dotted line) and c: match concussion incidence (solid line) in the period 2002 to 2019. Error bars show 95% CI for each season
Figure 2. Concussion incidence on a month by month basis for all years from 2002/03 to 2018/19. Box and whisker plot demonstrates maximum, minimum, interquartile range and median. Only 1 concussion was recorded in August and was therefore not included
The mean incidence of all match injuries of any type across the study period was 87/1000 hours (95% CI: 82–92), ranging between 62/1000 hours (95% CI: 57–69) and 103/1000 hours (95% CI: 94–108). The incidence of all injuries and of contact injuries (excluding concussion) did not change significantly over the study period (all injuries: B = −0.1, p = .93, contact injuries: B = −0.4, p = .31; ).
Time to Return-to-Play
Mean annual severity of diagnosed concussion over the whole study period was 13.0 days (95% CI: 10.6–15.4) and the median was 7.8 days (95% CI: 7.2–8.3). Both the mean (B = 0.5, p = .03, 95% CIs: 0.1–1.0) and median (B = 0.1, p = .01, 95% CIs: 0.03–0.2) severity of concussion rose significantly. Prior to the introduction of the GRTP, the average severity of concussion was 11 days (95%CIs: 8–14 days). After its introduction, the average severity was 15 days (95%CIs: 12–18 days: ). This change in the average severity is likely due to the decrease in the number of players returning in <6 days (the earliest return permitted under the GRTP guidelines) and the subsequent increase in the proportion of players returning during the 6–14 day period (). In the period after the introduction of the GRTP, 77% of players returned within two weeks, 86% within three weeks and 90% within four weeks. After its introduction, the proportion of players returning to play in <6 days decreased from 27% to 7%. Importantly, no players returned in <6 days from the 2014/15 season onwards (). Furthermore, since the introduction of the GRTP, the number of players that returned to full participation within a period allowing them to play in the next game (6 days) was 33%.
Table 2. Proportion of players returned to play in < 6 days, 6–14 days, 15–21 days, 22–28 days and >28 days for the period 2002/03 to 2018/19
DISCUSSION
The aim was to describe the trends in the incidence of match concussion and the time to return-to-play following concussion in professional rugby union. The highest incidence in 2016/17 is almost five times the incidence reported in previous seasons for this cohort (Citation2,Citation3). The incidence of concussion prior to the introduction of the HIA was 4.4/1000 hours, compared with the period after which was substantially higher at 15.1/1000 hours. The introduction of the GRTP substantially reduced the proportion of players returning in less than 6 days, with no players returning in less than 6 days after 2014/15.
Concussion Incidence
The incidence of concussion rose dramatically over the study period. On average, the rate rose 1/1000 hours (1 extra concussion every 25 matches) per year. However, this was driven by the substantial rise from 2009 to 2016/17 (2 extra concussions per 25 matches each year). To assist in the recognition of these injuries, a pitch side assessment tool (later called the HIA) was introduced in the 2012/13 season. It is clear that this tool significantly increased the reported incidence of concussion with the rate of concussion almost 3.5 times higher after the introduction of this assessment. Between the 2009/10 and 2016/17 seasons, the rate of concussion rose and peaked for the study period at 20.9/1000 hours, after which it appeared to stabilize. Between the 2016/17 and 2018/19 seasons, where a plateau appears to have occurred, the mean rate was 19.7/1000 hours, which is higher than the 13.8/1000 hours recently reported in one international team (Citation20), and similar to the 18.4/1000 hours reported in a professional Irish cohort (Citation4).
Does increased incidence truly reflect increased risk?
It is challenging to establish whether this change over time is a consequence of increased diagnosis and reporting of the injury or a genuine increase in risk of the injury occurring. It has been postulated that the risk of concussion has increased in professional rugby union as a result of the magnitude of the forces produced by heavier, faster, more powerful players (Citation21). However, changes in the anthropometric data in this cohort from 2002 to 2011 showed a small, gradual change over a 10-year period (Citation22) and more recently it has been reported that a plateau in body mass has occurred since 2011 in elite rugby union players (Citation23). Furthermore, a recent study of professional rugby union players in Ireland demonstrated only a small increase in total mass over a 7-year period which was attributed to an increase in lean mass and reduced body fat mass (Citation24). However, despite no significant change in player mass in recent seasons, it is not clear how other physical attributes such as speed, strength and power have changed over time.
A more notable change to the game is the increase in the number of tackles made per game. This is important given that tackles have been shown to be responsible for 43% of injuries within this cohort (Citation5). Between the 2013/14 and 2017/18 seasons there was an increase in the number of tackles per game in this league such that each team made an average of 102 tackles per match in 2013/14 compared with 139 tackles per match in the 2017/18 season (Citation25). This represents a 36% increase in the number of tackles, while the incidence of concussion increased by 70% over the same period and therefore cannot be accounted for by the increase in number of tackles alone. To further investigate this in the future, longitudinal reporting of the propensity of concussion per 1000 tackles events, in addition to per 1000 hours of match play, would add further valuable context.
Despite the increase in concussion incidence, the rate of overall injury has remained stable () and the proportion of all injuries which are concussions has increased (). In fact, non-concussion injuries have declined in a non-significant but meaningful manner (reduction of 1.25/1000 hours per year (Citation5)) which suggests a small decrease in overall injury rates (excluding concussions). Furthermore, the rate of non-concussion injuries caused by contact mechanisms () has not changed over time. Therefore, the specific increase in concussion incidence when the incidence of other injuries (including injuries in contact) is stable suggests a major contribution of increased reporting.
Another potential explanation for the increased incidence of concussion is that, as suggested in previous studies considering other sports (Citation26), it reflects increased awareness, understanding and improvements in reporting behavior amongst players, medical staff, coaches and referees who are now required to participate in mandatory education each season. Over the study period, changes to the recognition and diagnosis of concussion aligned with the introduction of an off pitch screen (later named the HIA) which includes a temporary concussion substitute as well as further standardized assessment after a match (HIA2) and 36–48 hours later (HIA3). Furthermore, the diagnostic criteria for reporting concussion have changed in this setting, with a lowering of the threshold used by clinicians to diagnose concussion (Citation27), leading to more cases being diagnosed over time. In 2012/13, the threshold for immediate removal from play, and by definition a diagnosis of concussion, comprised only 3 observable signs/criteria; confirmed loss of consciousness, tonic posturing; or concussive convulsions. In 2013/14 these signs/criteria were expanded to include suspected loss of consciousness, ataxia, and observable disorientation. In 2014/15, being clearly ‘dazed’ or ‘dinged,’ definite confusion and definite behavioral change were added to the list of criteria. Hence, the significant increase in the incidence of concussion during seasons 2013/14 and 2014/15 coincided with an expansion of the criteria for immediate removal (Citation28). It is therefore likely that a change in the diagnostic criteria for concussion over time has influenced what is actually being counted as a concussion in recent surveillance studies (Citation27).
Return-to-play
Players who return-to-play prematurely following concussion may further exacerbate symptoms and may have an increased risk of subsequent concussion (Citation29). Premature return-to-play may also be associated with catastrophic diffuse cerebral swelling following further impact (Citation30) and adverse long-term neurological outcomes (Citation31). In addition, recent studies in a range of sports have highlighted a 50–65% increase in the risk of further injury following return-to-play from concussion when compared with non-concussed, but injured, players (Citation32–34). The present study demonstrated a significant increase in mean and median time to return-to-play following concussion over the period 2002 to 2019. In addition, the number of players returning to play within 6 days decreased (7% compared with 27%) after the introduction of GRTP guidelines, highlighting the impact of changes in policy.
The significant change in the mean and median time to return can best be explained by examining the proportion of players returning within different severity groupings (<6 days, 6–14 days, 15–21 days, 22–28 days, >28 days) over the study period (). Comparing the periods after and before the introduction of the GRTP in 2011, the number of players returning in <6 days dropped significantly. Players who would previously have returned within <6 days, now returned within the 6–14 day period, indicated by the 77% of players returning within 14 days both pre- and post- the introduction of the GRTP. This suggests that the introduction of the GRTP in 2011 lengthened the time to return of those players whose clinical recovery was the swiftest. Further to this, the decrease in the number of players returning within <6 days following concussion (with none after the 2014/15 season) demonstrates the positive impact of the GRTP in preventing players from returning prior to what is currently recommended to be the shortest time for clinical recovery.
In the later seasons of the study period, there was an increase in the proportion of players who returned between 22–28 days as well as the proportion of people whose concussion led to a more than 4-week recovery. It is difficult to tell whether these changes are the result of a genuine increase in concussion severity or a more conservative approach to management of recovery by team doctors (and possible neurological specialist intervention). During the period 2002/03-2010/11, 89% of players returned within 3 weeks. The study methodology does not enable us to comment on the extent of the involvement of neurological specialists in determining the return to play.
The mean number of players returning earlier than the 6 days allowed by the GRTP protocol between 2012 and 2019 decreased to 7%, with no players returning in <6 days after 2015/16. These findings highlight the success of on-going player safety and stakeholder education initiatives in reducing the number of players returning to play in fewer days than the minimum stand down. It is recommended that these initiatives continue in order to sustain this improvement.
Future Directions
Regardless of the reasons for the substantial increase in diagnosed match concussion between 2009/10 and 2016/17, reducing the incidence of concussion in rugby union through effective injury prevention strategies is a clear priority. The majority of concussions in rugby occur in the tackle (Citation2,Citation3,Citation35,Citation36), making it a focus for primary prevention.
Further research is needed exploring the biomechanics during the concussion-collision mechanism to inform mitigation strategies such as law changes and coaching initiatives (Citation3). There are several video-based studies that have analyzed the tackle in rugby union (Citation35–40). The most recent of these studies demonstrates that a tackler at high speed and/or accelerating, a tackle involving head-to-head contact, and high tackles all lead to a higher risk of concussion in rugby union (Citation38,Citation39). A law variation that lowered the height of the legal tackle was evaluated in elite players, although the outcome was a non-significant increase in the incidence of concussion, with a significant increase in concussion incidence and propensity when tackling (Citation41). Other areas requiring further investigation to mitigate the risk of concussion include tackle technique training (Citation42), assessment of the effectiveness of the high tackle sanctions introduced by World Rugby, as well as exploration into the reduction of head impacts which do not lead to concussion. There have been recent advances in the validation of novel objective measures for concussion recognition, such as miRNA salivary tests (Citation43), however the lack of validated objective measures of recovery has to date limited the further refinement of the GRTP process on an individual level. While these are opportunities to target the reduction of concussion, it is clear that the dynamic and unpredictable nature of in-game tackle situations and subsequent head impacts makes reducing the risk of concussion a significant but critical challenge for the game.
Conclusion
Concussion is the most common injury in professional rugby union. Since the introduction of the HIA (to aid recognition and diagnosis) and GRTP protocol (to aid management and return-to-play), there have been significant increases in both the incidence and severity of concussion. It is not possible to separate improvement in reporting practice from the possibility of an inherent increase in the risk of concussion, but changes in the operational definition and reporting behavior and increased awareness of concussion are likely to have made a major contribution. The number of players returning to play before the recommended minimum time has improved significantly over time. Given the high incidence of concussion, it is essential to focus on strategies for primary prevention as well as evidence-based management of these complex brain injuries.
Declarations of Interest
This project was funded by the Rugby Football Union and Premier Rugby Ltd. SPTK, DL and KAS are employed by the Rugby Football Union. MJC is employed by Premier Rugby Ltd. GT has previously received grants from the Rugby Football Union and Premiership Rugby over the period 2011-16. The remaining authors have no competing interests to declare.
Acknowledgments
Funding for this study was provided by the Rugby Football Union, Premiership Rugby and University of Bath. The authors would like to thank the staff of the rugby clubs involved in this study for the ongoing collection of data which has helped to guide policy and improve player welfare across the game
Additional information
Funding
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