Concussion in the National Hockey League: a systematic review of the literature

Analysis of Player Performance and Financial Costs Associated With Implementation of an Updated National Hockey League Concussion Protocol: A Retrospective Comparative Study

Background

An updated National Hockey League (NHL) concussion protocol (NHLCP) was established in the 2016-2017 season to mitigate the negative outcomes of sport-related concussions. However, few studies on the effects of implementing the NHLCP have been performed.

Purpose

To define concussion incidence and investigate differences in NHL player performance after a concussion during periods before and after NHLCP implementation and assess the financial impact on NHL teams associated with NHLCP implementation.

Study Design

Cohort study; Level of evidence, 3.

Methods

This was a retrospective review of NHL players who sustained a concussion before (2000-2001 to 2015-2016 seasons) and after (2016-2017 to 2020-2021 seasons) implementing the NHLCP (pre-NHLCP and post-NHLCP groups). For each group, multiple performance metrics-including 30 days, 1 season, and 3 seasons before and after concussion-were compared for both groups. Return to play, total concussion cost, and association of return to play with cost were investigated using regression analysis.

Results

A total of 452 players (423 skaters, 29 goalies) sustained concussions during the study period, including 331 players (315 skaters, 16 goalies) in the pre-NHLCP group and 121 players (108 skaters, 13 goalies) in the post-NHLCP group. For both groups, no significant differences in standard performance were observed during the 30-day and 1-season periods before and after concussion. The mean return to play was significantly higher in the pre-NHLCP group than in the post-NHLCP group (20.1 vs 15.7 days; P = .022). The mean adjusted player salary was not different between groups; nonetheless, the mean adjusted replacement player salary was significantly higher in the post-NHLCP group ($744,505 vs $896,942; P = .032). The mean cost of time missed did not differ between groups. The mean return to play time significantly decreased over the entire study period (R2 = 0.33; P = .005), and the mean return to play time was positively associated with cost R2 = 0.215; P = .030).

Conclusion

Concussion incidence did not change after implementation of the updated NHLCP; nonetheless, players had significantly less missed time from injury after protocol implementation. Changes in player performance 30 days and 1 year before and after concussion injury were not different before and after NHLCP implementation. No differences were found in the financial cost of concussions between the pre- and post-NHLCP groups, and missed time was significantly correlated with mean cost from missed time.

It's in the game: A review of neurological lesions associated with sports

INTRODUCTION

The practice of sports may lead to neurological injuries. While relatively uncommon (overall incidence of approximately 2.5%), and mostly benign and transient, some conditions may be life-threatening and permanent. Thus, both clinical neurologists and sports physicians should be aware of their existence and relevance. We aimed to review all sports-related neurological injuries and illnesses reported in the literature.

METHODS

Following SANRA guidelines, we performed a narrative review and searched PubMed and Scopus databases. Relevant sports were selected based on their recognition as an Olympic sport by the International Olympic Committee. Chronic traumatic encephalopathy (CTE) and other neurodegenerative disorders were not included.

RESULTS

A total of 292 studies were included concerning 33 different sports. The most reported neurological injury was damage to the peripheral nervous system. Traumatic injuries have also been extensively reported, including cerebral haemorrhage and arterial dissections. Non-traumatic life-threatening events are infrequent but may also occur, e.g. posterior reversible encephalopathy syndrome, cerebral venous thrombosis, and arterial dissections. Some conditions were predominantly reported in specific sports, e.g. yips in baseball and golf, raising the possibility of a common pathophysiology. Spinal cord infarction due to fibrocartilaginous embolism was reported in several sports associated with minor trauma.

CONCLUSION

Sports-related neurological injuries are increasingly receiving more social and medical attention and are an important cause of morbidity and mortality. This review may serve as a guide to physicians managing these challenging situations.

Fighting in professional ice hockey: it's time for a change

Ice hockey has long been defined by a level of violence not seen in other sports. The rough-and-tough vigilante nature of the game was often employed as a method of enticing fans. Play in the National Hockey League (NHL) evolved throughout the 20th century as the rules governing it did. The nuances of what was allowed on the ice was slowly defined, but the league always fell short of an outright ban on fighting. Notably, the NHL allows fighting while international and Olympic leagues do not. Proponents of fighting's continued presence in the NHL argue that it can attract fans, facilitate momentum changes, help win games, and allows for social regulation on the ice. However, analyses of these theories have found little definitive evidence, calling the utility of fighting into question. The economics of fighting in hockey reveal high salary payouts, increased cost of injury, and a lack of correlation with ticket sales. Additionally, there is a concern for concussions sustained during fighting which has the potential for long term, detrimental mental health effects for athletes. In this analysis, we explore the history and evolution of fighting in the NHL, as well as the reasons behind its continued presence in the game, the risks associated with fighting, and the economics behind it all. Based upon these bodies of evidence, we make a proposal regarding the future of fighting in the NHL.

The Effects of Modified Game Schedules on Injury Rates in the National Hockey League (NHL)

Background Due to the COVID-19 pandemic, many professional sports leagues such as the National Hockey League (NHL) made significant changes to their schedules and operating procedures. Changes included a modified 2019-2020 playoff format, the removal of the 2020-2021 preseason, and condensed game schedules. Though these modifications were made in an effort to protect players from COVID-19, they resulted in decreased training time and preparation. The purpose of this study was to assess the impact of these changes on the rate of player injuries in the NHL both after the resumption of the midseason stoppage and during the subsequent seasons. Hypothesis/purpose Changes to the NHL schedule amid the COVID-19 pandemic resulted in a significant increase in player injury rates. Methods NHL injuries were obtained from an NHL injury database for the 2018-2019 through the 2021-2022 seasons. The date of injury, date of return, injury description, player age, and player position were recorded. Injury rates were calculated as the number of total athlete injuries per 1000 game exposures (GEs). The primary outcome was the injury proportion ratio (IPR) when comparing the injury rates of the post-COVID-19 season with baseline seasons. Secondary measures analyzed injuries based on age, anatomic location, month in the season, position, length of injury, season-ending injuries, and recurring injuries. Results A total of 4604 injuries were recorded between 2018 and 2022. The modified 2019-2020 playoffs had significantly higher rates of injury (IPR = 1.84, 95% confidence interval {CI} = 1.36-2.49) with more game exposures per week. The 2020-2021 season had significantly higher rates of overall player injury compared to baseline seasons (IPR = 1.19, 95% CI = 1.09-1.30) and also had a higher rate of season-ending injuries (IPR = 1.71, 95% CI = 1.38-2.11). Most injuries occurred in the first few months of the 2020-2021 season. There was no significant difference in injury rate based on age group and no significant difference in the average length of injury between seasons. Conclusion Increases in injury rates could be due to decreased offseason training between seasons, the elimination of preseason games, and increased game density. Decreasing typical training timelines and eliminating the preseason to rapidly return to normal competition after unexpected events (pandemics, lockdowns, etc.) may pose a risk to player safety in the NHL. These findings should be considered before future schedule changes in professional hockey.

Fighting to the death: Does hockey fighting in the NHL affect players' longevity?

Hockey is a sport known for its violent nature. Specifically, hockey fights have consistently been an integral part of the National Hockey League. Past research has demonstrated that players are likely to be involved in fighting as a mechanism to gain fan support, generate game momentum or enhance team camaraderie. However, fighting naturally has negative health ramifications. In the current study, we sought to investigate if players' involvement in hockey fights throughout their career was associated with shorter life spans. Previous mortality studies have not distinguished hockey fighting from other aggressive aspects of this sport (e.g., in game physical contact with other players). We conducted an archival study examining the frequency of hockey fighting during the 1957-1971 NHL seasons and player longevity. A Kaplan-Meier survival analysis log-rank method and a subsequent Cox regression accounting for correlates showed no relationship between an elevated number of fights and a reduced lifespan. The lack of effect may indeed demonstrate a negligible influence on long-term health consequences in the context of a generally very physical game. However, with the relatively moderate levels of fighting in the period studied we recommend that the association be explored also in a subsequent era when NHL fighting peaked.

Concussions in the Women's National Basketball Association: Analysis of Incidence, Return-to-Play Timing, and Player Performance From 1997 to 2020

Background:

The extent to which concussions affect Women’s National Basketball Association (WNBA) athletes has not been thoroughly examined.

Purpose:

To evaluate the incidence and impact of concussion injuries occurring in the WNBA.

Study Design:

Descriptive epidemiology study.

Methods:

Publicly available records were searched to identify all documented basketball-related concussions from WNBA seasons 1997 to 2020. Player demographics, injury details, and basketball career information were collected. Concussion incidence and return-to-play (RTP) timing were evaluated before and after the institution of the WNBA concussion protocol in 2012. Minutes per game and game score per minute were compared 5 games before and 5 games after the concussion was sustained. Player game availability and RTP performance were also compared with an age-, body mass index–, position-, and experience-matched control group of players who did not sustain any injuries during the index season.

Results:

A total of 70 concussions among 55 players were reported in the WNBA from 1997 to 2020, with a mean incidence of 2.9 ± 2.3 concussions per season. After the implementation of the WNBA concussion protocol, the incidence significantly increased from 1.7 to 5.0 concussions per season (P < .001). All players returned after a first-time concussion, missing a mean of 3.8 ± 4.7 games and 17.9 ± 20.7 days. After the adoption of the concussion protocol, the time to RTP significantly increased with games missed (P = .006) and days missed (P = .006). Minutes per game and game score per minute were not significantly affected by sustaining a concussion (P = .451 and P = .826, respectively).

Conclusion:

Since the adoption of the WNBA concussion protocol in the 2012 season, the incidence of concussions increased significantly. Athletes retained a high rate of RTP after missing a median of 4 games, and the time to RTP increased after the institution of the concussion protocol. Player game availability and performance within the same season were not significantly affected by concussion injuries after a successful RTP.

Concussions in the National Hockey League: Analysis of Incidence, Return to Play, and Performance

Background:

Concussion injuries are common in professional hockey; however, their effect on player performance remains unclear.

Purpose:

To quantify the effect of concussions on the performance of position players in the National Hockey League (NHL).

Study Design:

Cohort study; Level of evidence, 3.

Methods:

Concussion data from the NHL were collected using publicly available databases for the seasons between 2009-2010 and 2015-2016, coinciding with new NHL concussion rules. Age, body mass index, position, number of concussions during a player’s NHL career, games played, and time on ice were recorded. Basic and advanced performance metrics were collected for 1 season pre- and postconcussion (short-term period) and 3 seasons before and after concussion (long-term period) to assess short- and long-term changes in performance. A control group of players without an identified concussion who competed during the study period was assembled for comparison. Wilcoxon signed rank tests were used to evaluate pre- to postconcussion data in the short- and long-term settings as well as to compare the cohorts at each time point.

Results:

Overall, 48 players were identified as having a concussion during the study period. Players missed 17.2 ± 15.1 days (mean ± standard deviation) and 7.5 ± 6.9 games postconcussion. There were no significant differences in any metric when pre- and postconcussion intraseason performance was assessed. Athletes who were concussed demonstrated significantly deceased performance metrics (assists per 60 minutes, points per 60 minutes, Corsi percentage, and Fenwick percentage) in the 3 years after the concussion as compared with the year before injury ( P < .05). However, no difference was found between the concussed group and matched control group in the short- or long-term period. Players with concussion played fewer career games (856.4 ± 287.4 vs 725.7 ± 215.0; P < .05) than did controls.

Conclusion:

A high rate of NHL players were able to return to play after a concussion injury. Players with concussion did not experience a reduction in performance metrics in the short- or long-term setting when compared with matched controls. The concussed cohort maintained a similar workload up to 3 seasons postconcussion but played in fewer career games when compared with matched controls.

Incidence of Head Contacts, Penalties, and Player Contact Behaviors in Youth Ice Hockey: Evaluating the “Zero Tolerance for Head Contact” Policy Change

Background:

To reduce the risk of concussion in youth ice hockey, Hockey Canada implemented a national “zero tolerance for head contact” (HC) policy in 2011. A previous cohort study revealed higher concussion rates after this implementation in players aged 11 to 14 years. However, it is unknown whether the elevated risk was due to higher HC rates or factors such as increased concussion awareness and reporting.

Purpose:

To compare the rates of primary and secondary HCs and HC policy enforcement in elite U15 ice hockey leagues (players <15 years) before (2008-2009) and after (2013-2014) the zero-tolerance policy change.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

A total of 32 elite U15 games before (n_2008-2009 = 16; 510 players) and after (n_2013-2014 = 16; 486 players) HC policy implementation were video recorded. Videos were analyzed with validated criteria for identifying HC types (primary/direct contact by players [HC1], secondary/indirect contact via boards, glass, or ice surface [HC2]) and other player-to-player contact behavior. Referee-assessed penalties were cross-referenced with the official Hockey Canada casebook, and penalty types were displayed using proportions. Univariate Poisson regression (adjusted for cluster by team game, offset by game length [minutes]) was used to estimate HC incidence rates (IRs) and incidence rate ratios (IRRs) between cohorts.

Results:

A total of 506 HCs were analyzed, 261 before HC policy implementation (IR, 16.6/100 team minutes) and 245 after implementation (IR, 15.5/100 team minutes). The HC1 rate (IRR, 1.05; 95% CI, 0.86-1.28) and HC2 rate (IRR, 0.74; 95% CI, 0.50-1.11) did not significantly differ before versus after implementation. Only 12.0% and 13.6% of HC1s were penalized pre- and postimplementation, respectively. Before implementation, HC1s were commonly penalized as roughing or elbowing penalties (59%), while after implementation, HC1s were penalized with the HC penalty (76%), and only 8% as roughing or elbowing.

Conclusion:

Despite implementation of the “zero tolerance for HC” policy, there was no difference in the rate of HC1s and HC2s or the proportion of HC1 penalized from before to after implementation. This research is instrumental in informing Hockey Canada’s future referee training and rule enforcement modifications.

The Epidemiology of Sport-Related Concussion: What the Rehabilitation Clinician Needs to Know

Sport-related concussion is common in full-contact and collision sports. Epidemiology studies use different types of surveillance systems and concussion definitions. Concussion incidence rates vary across age, sex, sport, and level of competition. Incidence rates are increasing, likely due to higher rates of reporting following improved knowledge and increased regulations. In this review, we summarize 7 key concepts related to concussion epidemiology: concussion definition, changes in concussion knowledge, reliability and accuracy of injury surveillance systems, conservative management and return to play, reliability of self-report, incidence of concussion across levels of play, and understanding the behaviors of players, coaches, and medical personnel from a multidisciplinary management perspective. J Orthop Sports Phys Ther 2019;49(11):768-778. doi:10.2519/jospt.2019.9105.

Concussions in the National Basketball Association: Analysis of Incidence, Return to Play, and Performance From 1999 to 2018

BACKGROUND

The effect of concussions on professional athletes has been investigated in many sports. However, few studies have evaluated concussions in National Basketball Association (NBA) players.

HYPOTHESIS

We hypothesized that concussion incidence has increased, yet the return-to-play (RTP) rate will remain high following the institution of the NBA concussion policy (NBACP). We also hypothesized that the incidence of repeat concussions will be similar to first occurrences and that player performance and game availability will not be significantly affected by sustaining a concussion.

STUDY DESIGN

Descriptive epidemiology study.

METHODS

Publicly available records were searched to identify all concussions from NBA seasons 1999-2000 to 2017-2018. Player demographics and information regarding career history were tabulated. Incidence of concussion and RTP timing were evaluated before and after institution of the NBACP (2011). Minutes per game and game score per minute were evaluated pre- versus postconcussion. Player availability and performance were also compared with an age-, body mass index-, position-, and experience-matched control group of players who did not sustain a concussion.

RESULTS

A total of 189 concussions were reported in the NBA from 1999 to 2018, with a mean ± SD incidence of 9.7 ± 7.3 concussions per season. Following implementation of the NBACP, incidence significantly increased from 5.7 ± 2.8 to 16.7 ± 7.5 concussions per season (P = .007). All players returned to play following first-time concussion after missing 7.7 ± 8.6 days and 3.5 ± 4.1 games. RTP time was not significantly different after implementation of the NBACP (games missed, P = .24; days missed, P = .27), and there was no difference in concussion-free time interval (P = .29). Game score per minute and minutes per game were not significantly affected by sustaining a concussion (both P > .05).

CONCLUSION

Concussion incidence in NBA players is approximately 17 instances per season since the 2011 institution of a league-wide concussion policy. The number of reported concussions significantly increased following the policy, in line with trends seen in other professional sports leagues. Players have retained a high rate of RTP after 3 to 4 missed games. Player performance and availability are not affected by sustaining a concussion following successful RTP.

Concussion and National Hockey League Player Performance: An Advanced Hockey Metrics Analysis

CONTEXT

Postconcussion deficits in neurocognitive performance and postural control may persist at the time of return to sport participation. How these deficits, if present, affect athletic performance is largely unknown, with prior studies showing mixed results.

OBJECTIVE

To evaluate postconcussion National Hockey League player performance using advanced hockey metrics over short- (5 games), medium- (10 games), and long-term (remainder of the season) seasonal performance.

DESIGN

Retrospective cohort study.

PATIENTS OR OTHER PARTICIPANTS

National Hockey League players who sustained a sport-related concussion (SRC; n = 93) and returned during the same season and players (n = 51) who missed time for non-injury-related reasons.

MAIN OUTCOME MEASURE(S)

Six performance metrics were used: (1) points per 60 minutes, (2) Corsi percentage, (3) personal Fenwick shooting percentage, (4) scoring chances per 60 minutes, (5) penalty difference, and (6) PDO (not an acronym but sometimes referred to as SVSP% [save percentage shooting percentage]). Performance was compared using 2 (group) × 2 (time) repeated-measures analyses of variance for 3 time windows: (1) ±5 games, (2) ±10 games, and (3) the remainder of the season postconcussion. Alpha values were set at a conservative .01 to account for the lack of independence among dependent variables.

RESULTS

No significant interactions were present for any of the 6 dependent variables at any of the 3 time windows. Overall, none of the secondary variables differed.

CONCLUSIONS

Using advanced, sport-specific metrics, we found that National Hockey League players did not display worse seasonal performance during 3 postinjury time frames after they sustained an SRC. Whereas laboratory studies have identified lingering neurologic deficits after concussion, our results suggest that these deficits, if present, either do not translate to worse athletic performance or were not captured by these 44 metrics. Further, prospective efforts are needed to accurately quantify performance after SRC among professional hockey players.