Precis:
Though boxing had a greater incidence of eye injuries than mixed martial arts (MMA), MMA injuries more frequently required physician evaluation with higher rates of orbital fractures and injury to the face or body.
Purpose:
To evaluate and compare eye and face trauma in mixed martial arts (MMA) and boxing.
Design:
Retrospective cohort study
Methods:
Data from boxing and MMA competitions were extracted from the Nevada Athletic Commission (NAC) between 2000–2020. Details of competitions, contestants, outcomes and injuries were extracted.
Results:
1539 boxing injuries (from 4313 contests) and 1442 MMA injuries (from 2704 contests) were identified. Boxing had higher eye injury rates compared to MMA (p<0.0001), with OR of 1.268 (95% CI 1.114–1.444). Eye trauma represented 47.63% of boxing and 25.59% of MMA injuries, with periocular lacerations being the most common eye injury in both. Orbital fracture represented 17.62% of eye injuries in MMA and 3.14% in boxing contests. 2–3% were retinal in both sports and 3.27% were glaucomatous in boxing. MMA contestants had an OR of 1.823 (95% CI 1.408–2.359) for requiring physician evaluation following eye injury compared to boxing. MMA contestants also had a higher rate of face (p<0.0001) and body (p<0.0001) injuries. For both sports, increased number of rounds and being the losing fighter were associated with increased odds of eye and face injury.
Conclusion:
Although boxing has a higher rate of eye injuries, MMA eye injuries are more likely to require physician evaluation. MMA contestants also have a higher rate of orbital fractures and face and body trauma. Detailed post-fight examination and long-term follow up of ocular injury in combat sports will be vital in proposing reforms to prevent eye trauma.
Keywords: eye trauma, combat sports, mixed martial arts, MMA, boxing, facial trauma, orbital trauma, orbital fracture
Introduction
Combat sports are competitive contact sports that usually involve one-on-one combat and include boxing, wrestling, judo, Tae Kwon Do, kickboxing, and many others. In 2008, over 200 Olympic medals were given to athletes in combat sports.1 Although the earliest evidence of boxing dates back to Egypt around 3000 BC, the sport known today as mixed martial arts (MMA), or ultimate fighting, did not start in the US until 1993. MMA has been called the world’s fastest-growing sport.2 A poll conducted by The Washington Post and UMass Lowell found that 28% of Americans count themselves as fans of professional boxing and 25%, or 1 in 4, are fans of MMA.3 Another indicator of its popularity came with ESPN signing a five-year $1.5 billion rights broadcasting deal for the Ultimate Fighting Championship (UFC) in 2018.4
The first MMA fights were fought with virtually no protective gear, weight classes, time limits, or other regulatory standards. This brought significant criticism5 by some parties over a perceived lack of care for the athletes’ safety. Since its inception, specific rules and regulations to promote combat fighter safety have been established. The framework of the Unified Rules of MMA was proposed and agreed upon by various athletic commissions in the early 2000s, but this was not unanimously adopted by the Association of Boxing Commissions (ABC) until 2009.6 For boxing which has been around longer, regulations and gear (gloves, mouth guards, etc) have been implemented and advanced over the years to protect athletes.
Severe eye injuries in combat sports have made national news. Both boxing and MMA are unique sports in that they both deliberately aim to produce head injuries – a knock out is a win. The concern with eye or periocular injuries is that with vision obscured, the contestant is at a severe disadvantage and therefore, is likely at increased risk for additional injuries. Eye injuries in combat sports are not necessarily a new phenomenon. Boshoff and Jokl presented several cases of ocular injury in boxing in 1948.7 Whereas there are several publications describing eye injuries in boxing,8–13 few authors have published on injuries in MMA. A recent publication by Fliotsos et al. characterizes the prevalence and types of eye injury in mixed martial arts.14 Our study adds to the current literature by comparing the incidence and types of eye, face, and body injuries between two combat sports and identifying the risk factors for these injuries.
Nevada has hosted the greatest number and most prominent professional MMA and boxing fights in the US.15 Based on data collected from matches in Nevada, the Nevada Athletic Commission has made formal recommendations to protect the health and safety of competitors. Herein, we use data from the Nevada Athletic Commission to evaluate and compare eye and face trauma in both boxing and MMA.
Methods
Study Design
A retrospective cohort study was conducted to examine eye, face, and body injuries in boxing and mixed martial arts competitions in the state of Nevada from January 14, 2000 to May 30, 2020. Results of the events were previously available on the Nevada State Athletic Commission (NSAC) website (boxing.nv.gov, last accessed September 2020).
The seven objectives of the research study were to determine: 1) the cumulative incidence of eye, face, and body injuries in MMA and boxing; 2) whether one type of combat sport had more eye and face trauma; 3) the types of eye and face trauma reported for MMA and boxing; 4) the number of fighters requiring physician evaluation or clearance; 5) the types of medical work-ups noted for fighters; 6) the risk factors for eye, face, and body trauma in MMA and boxing; and 7) whether gender or race affected risk for eye, face, or body trauma in MMA and boxing.
This study was approved by the University of California, San Francisco Institutional Review Board (IRB) and conducted in compliance with the rules and regulations of the Health Insurance Portability and Accountability Act and all applicable federal and state laws, and in adherence to the tenets of the Declaration of Helsinki.
Combat Sports Database
The study dataset contained the following information obtained from the Nevada Athletic Commission website: fight date, fight location, fight type (boxing vs. MMA), competitor names, competitors’ date of birth, competitors’ weight, original number of rounds, actual number of rounds fought, match outcome (win, loss, or draw), how the match ended (disqualification, draw, no contest, no decision, split decision, majority decision, tap-out, technical knockout (TKO), and knockout (KO)), name of referee, fight violations, presence of eye/face/body trauma, comments on eye/face/body trauma, and work-up for eye/face/body trauma. Location, type, work-up, and description for injuries were collected using keyword queries. Once the keywords were detected, the injury comment noted by the Athletic Commission would be moved into the spreadsheet. For eye injury, the query terms were “eye”, “eyelid”, “orbit”, “orbital”, “ophthalmology”, “plastic”. For facial injury, the query terms were “face”, “facial”, “cheek”, “head”, “forehead”, “scalp”, “nose”, “nasal”, “lip”, “jaw”, “tooth”, “ear”, “eardrum”. For body injury, the terms used were “ankle”, “back”, “bicep”, “bone”, “chest”, “digit”, “elbow”, “hand”, “wrist”, “knee”, “leg”, “pain”, “rib”, “shoulder”, “thumb”. The work-up for injuries included additional keywords related to specialty (“Ophthalmology”, “ENT”, “Neuro”, “Plastic”, “Doctor”, “Surgeon”) and evaluation (“Cleared”, “Clearance”, “Evaluation”, “Imaging”, “XR”, “MRI”, “CT”, “Follow-up”). To assign inferred race/ethnicity to each combatant for further analysis, the “wru” package16,17 was used in R18 to obtain Bayesian prediction probabilities of race/ethnicity category based upon surname and location. To assign inferred gender for analysis, the “gender” package19,20 was used in R to predict gender based upon first names and year of birth, and less certain probabilities were further enriched based upon combatant’s assigned gender probabilities. After assigning inferred race/ethnicity and gender, we conducted a validation study by selecting a random sample of 120 fighters and two authors independently annotated gender and ethnicity based on manual search engine results. We then validated the machine-encoded gender classification to human-assigned classifications, with 95–99% agreement for gender and 75–80% agreement for race/ethnicity. Of note, the machine-encoded method assigned probabilities for race/ethnicity and was analyzed as a continuous variable as a proxy for predicted race/ethnicity.
Terminology and Definitions
In our study, we used three categories for injury based on anatomy: eye, face, and body. Eye injuries were classified by the study team as trauma involving the eyeball, eyelid, eyebrow, or orbital wall. Face injuries were classified as trauma involving the scalp, forehead, nose, maxillary sinus, cheek, jaw, lips, tongue, and teeth. All other injuries outside of the head and neck, including upper and lower extremities, chest, back, and groin, were classified as body injuries. The classification of boxing and mixed martial arts weight classes and match results are outlined in Supplemental Table 1.
Statistical Analysis
Cumulative incidence was represented as injury rate, defined as the number of injuries divided by the number of fighters or rounds and multiplied by a constant (per 100 fighters or 100 contested rounds). The percentage of original rounds fought was defined as the number of contested rounds divided by the original number of rounds allocated for the fight. Continuous variables of age, weight, and number of rounds fought were compared using student’s t test and Mann-Whitney U Test. Comparisons of categorical variables including type of combat fight (boxing vs. MMA) were performed using the chi-square test and Fisher’s exact test, where appropriate. Risk factors of age, weight, weight class, round number, fight result (winning vs. losing), type of win, and referee were analyzed first, using univariate logistic regression, and then using multivariable logistic regression. For weight class, type of win, and referee, the reference category was selected based on the closest representation of the population control and with the largest sample size. For boxing and MMA contests, welterweight and bantamweight, were used as the reference category for weight class, respectively. Unanimous decision was used as the reference category for type of win. Regression models were fitted for eye injury, face injury, and body injury. To avoid overfitting in the multivariate model, we included six variables: age, gender, predicted race/ethnicity, weight, round number, and fight result. Statistical analyses were performed using IBM SPSS Statistics (Version 23.0).
Results
Demographics
During the study period from 2000–2020, there were a total of 4313 boxing contests and 2704 MMA contests. Boxing had a total of 8626 contestants of which 8.0% were female and 92.0% were male, while MMA had 5408 contestants, 8.3% female and 91.7% male. The average age of boxing contestants (26.8 years) was lower than MMA (28.2 years) (p<0.0001), and the average weight of boxing contestants (153.7 lbs) was less than MMA (170.74 lbs) (p<0.0001). There were no differences in the percentage of original rounds fought between boxing and MMA (71.43% vs. 71.14%, p=0.7). However, boxing contests were longer in duration than MMA fights, with a higher number of rounds for each fight (Table 1).
Table 1: Demographics and types of finishes for boxing and MMA matches.
| Boxing | MMA | p value | |
|---|---|---|---|
| Demographics | |||
| Total number of fights | 4313 | 2704 | .. |
| Total number of fighters | 8626 | 5408 | .. |
| Sex | |||
| Female | 692 (8.0%) | 456 (8.3%) | 0.40 |
| Male | 7934 (92.0%) | 4958 (91.7%) | 0.40 |
| Age, years | 26.8 (26.7–26.9) | 28.2 (28.1–28.3) | <0.0001 |
| Weight, pounds | 153.7 (152.9–154.5) | 170.7 (169.8–171.6) | <0.0001 |
| Total original number of rounds | 31357 | 8260 | .. |
| Average original number of rounds | 7.3 (7.2–7.4) | 3.0 (2.9–3.1) | <0.0001 |
| Total number of contested rounds | 21790 | 5790 | .. |
| Average number of contested rounds | 5.0 (4.9–5.1) | 2.1 (2.0–2.2) | <0.0001 |
| Percentage of original rounds fought | 71.4 (70.4–72.4) | 71.1 (70.0–72.3) | 0.71 |
| Types of Finishes | |||
| Knockout (KO) | 392 (9.1%) | 110 (4.1%) | .. |
| Technical knockout (TKO) | 1599 (37.1%) | 786 (29.1%) | .. |
| Tap out | .. | 724 (26.8%) | .. |
| Unanimous decision | 1618 (37.5%) | 800 (29.6%) | .. |
| Majority decision | 219 (5.1%) | 60 (2.2%) | .. |
| Split decision | 193 (4.5%) | 173 (6.4%) | .. |
| Draw | 198 (4.6%) | 20 (0.7%) | .. |
| No contest | 72 (1.7%) | 18 (0.7%) | .. |
| Disqualification | 22 (0.5%) | 13 (0.5%) | .. |
Data for age, weight, and round numbers are means (95% CI). p values were calculated by Mann-Whitney U test or Student’s t test, as appropriate.
In boxing contests, most fights resulted in unanimous decision (37.5%) or TKO (37.1%). The less-frequent results were fights ending in KO (9.1%), majority decision (5.1%), draw (4.6%), split decision (4.5%), no contest (1.7%), and disqualification (0.5%).
In MMA contests, most fights resulted in unanimous decision (29.6%), TKO (29.1%), or tap-out (26.8%). Less frequent fight results included split decisions (6.4%), KO (4.1%), majority decision (2.2%), tie (0.7%), no contest (0.7%), and disqualification (0.5%).
Injury Rates
A total of 1539 injuries were identified in boxing contests, representing 35.68 injuries per 100 boxing competitions. The all-cause injury rate for boxing contests was 17.84 injuries per 100 fighters or 7.06 injuries per 100 contested rounds. The rate of boxing eye injuries was 8.50 injuries per 100 fighters or 3.36 injuries per 100 contested rounds. There were 4.88 face injuries per 100 boxing contestants or 1.93 face injuries per 100 contested rounds and 4.46 body injuries per 100 boxing contestants or 1.77 body injuries per 100 contested rounds.
For MMA, 1442 total injuries were identified, representing 53.33 injuries per 100 MMA competitions. The all-cause injury rate was significantly higher for MMA fights compared to boxing (p<0.0001), with 26.66 injuries per 100 fighters or 24.91 injuries per 100 contested rounds. The rate of MMA eye injuries was 6.82 per 100 fighters or 6.37 per 100 contested rounds. There were 8.65 face injuries per 100 fighters or 8.08 per 100 contested rounds and 11.19 body injuries per 100 fighters or 10.45 per 100 contested rounds.
Eye Injury
There was a significant association between type of combat fight with eye injury. Boxing contestants had a higher eye injury rate compared to MMA (p<0.0001), with OR 1.268 (95% CI 1.114–1.444). Eye trauma represented 47.63% of injuries in boxing, while 25.59% in MMA (Figure 1). The types of eye injuries for boxing and MMA contestants are displayed in Figure 1. Other or unspecified injuries for boxing contestants include cataract (0.27%), traumatic mydriasis (0.14%), and double vision (0.14%). Other or unspecified injuries for MMA contestants include hematoma (0.54%), traumatic mydriasis (0.54%), conjunctival laceration (0.27%), ocular irritation (0.27%), and subconjunctival hemorrhage (0.27%). Boxing contestants experienced a higher proportion of eyelid lacerations (p<0.0001) and glaucoma evaluations (p=0.001) but no difference in eyebrow lacerations (p=0.87), while MMA contestants experienced a higher proportion of orbital wall fractures (p<0.0001).
Figure 1. Proportion of injury location and types of eye injuries for boxing and mixed martial arts.
Percentage values displayed represent number of eye/face/body injuries divided by the total number of injuries and the number of cases per eye injury type divided by total number of eye injuries.
For boxing contestants, 227 of 733 eye injuries (30.97%) required physician clearance before the next fight, while in MMA, 166 of 369 eye injuries (44.99%) warranted physician clearance (p<0.0001). MMA contestants had an OR 1.823 (95% CI 1.408–2.359) for requiring physician evaluation following an eye injury compared to boxing contestants. However, a greater number of ophthalmology specialty referrals were placed for boxing contestants compared to MMA (43 vs. 13), with 23 boxing referrals for a glaucoma specialist compared to 2 glaucoma referrals for MMA. A small number of imaging studies were suggested for fighters of both boxing and MMA, 16 and 17 respectively.
Face Injury
MMA contests had a higher rate of face injuries compared to boxing (p<0.0001), with MMA fighters having 1.846 (95% CI 1.611–2.116) times increased odds for face injury compared to boxing competitors. Face trauma consisted of 27.36% of boxing injuries and 32.45% of MMA injuries. The types of face injuries for boxing and MMA contestants are displayed in Figure 2. Other or unspecified face injuries for boxing include facial fracture (0.95%), facial hematoma (0.71%), and maxillary sinus fracture (0.24%). Other or unspecified face injuries for MMA include facial fracture (0.64%), cheek hematoma (0.21%), and tongue laceration (0.21%). Boxing contestants experienced a higher proportion of head blow injuries (p<0.0001), while MMA contestants had a higher proportion of nose fracture (p=0.002) and facial lacerations (p<0.0001).
Figure 2. Proportion of types of face injuries for boxing and mixed martial arts contestants.
Percentage values displayed separately for boxing and mixed martial arts contestants represent number of cases per type of face injury divided by the total of number of face injuries for the specific combat sport.
Boxing and MMA had similar rates of physician clearance for face injury before the next fight. For boxing contestants, 135 of 421 face injuries (32.07%) required physician clearance, while in MMA, 177 of 468 (37.82%) needed clearance (p=0.07). Specific referrals to ENT physicians were placed for 85 of 135 (62.96%) boxing face injuries and 112 of 177 (63.28%) MMA face injuries, while 74 and 47 imaging studies were requested for boxing and MMA respectively.
Body Injury
MMA contests also had a higher rate of body injuries compared to boxing (p<0.0001), with MMA fighters having 2.696 (95% CI 2.361–3.079) increased odds for body injury compared to boxing competitors. Body injuries were noted in 25.01% of boxing and 41.96% of MMA contests. The types of body injuries for boxing and MMA contestants are displayed in Figure 3. Of note, there were no deaths for fighters in our database. Boxing contestants experienced a higher proportion of hand injuries (p<0.0001) compared to MMA but without any significant difference in wrist injuries (p=0.50). MMA contestants experienced a higher proportion of elbow (p=0.001), knee (p<0.0001), foot (p<0.0001), and ankle injuries (p=0.01) compared to boxing contestants.
Figure 3. Proportion of types of body injuries for boxing and mixed martial arts contestants.
Percentage values displayed separately for boxing and mixed martial arts contestants represent number of cases per type of body injury divided by the total number of body injuries for the specific combat sport.
Risk Factors
In separate univariate regression models for boxing and MMA contests, older age, male gender, increased number of rounds, and being the losing fighter were associated with increased odds of eye and face injury. Female contestants were found to have significantly lower odds of eye, face, and body injuries in MMA and decreased odds for eye injury in boxing. Fights that ended with knock-out, technical knock-out, or tap out lowered the odds of eye and body injury, but not for face injury. Race or ethnicity, weight in pounds, weight class, referee, and individual fighter were not significantly associated with eye, face, or body injuries (Table 2, Table 3).
Table 2. Odds of eye injury associated with risk factors in boxing and mixed martial arts competitors.*.
| Univariate OR (95% CI) | p value | Multivariate OR (95% CI) | p value | |
|---|---|---|---|---|
| Boxing competitor characteristics (Eye Trauma Model) | ||||
| Age, years | 1.04 (1.02–1.06) | <0.0001 | 1.03 (1.01–1.05) | 0.004 |
| Sex | ||||
| Female | 0.49 (0.34–0.71) | <0.0001 | 0.46 (0.32–0.68) | <0.0001 |
| Male | 2.05 (1.41–2.99) | <0.0001 | 2.17 (1.47–3.13) | <0.0001 |
| Predicted race or ethnic group | ||||
| Asian | 0.58 (0.25–1.36) | 0.21 | 0.59 (0.25–1.37) | 0.22 |
| Black | 0.81 (0.52–1.28) | 0.37 | 0.75 (0.47–1.19) | 0.22 |
| Hispanic or Latino | 0.98 (0.82–1.17) | 0.81 | 1.03 (0.86–1.23) | 0.77 |
| White | 1.14 (0.91–1.43) | 0.27 | 1.08 (0.86–1.36) | 0.52 |
| Weight, pounds | 0.996 (0.994–0.999) | 0.002 | 0.996 (0.993–0.998) | 0.001 |
| Weight class a | ||||
| Strawweight | 0.51 (0.19–1.41) | 0.19 | .. | .. |
| Flyweight | 1.51 (0.86–2.65) | 0.15 | .. | .. |
| Bantamweight | 0.92 (0.66–1.29) | 0.63 | .. | .. |
| Featherweight | 1.08 (0.84–1.39) | 0.56 | .. | .. |
| Lightweight | 1.08 (0.81–1.44) | 0.60 | .. | .. |
| Middleweight | 1.15 (0.90–1.46) | 0.26 | .. | .. |
| Cruiserweight | 0.85 (0.57–1.27) | 0.42 | .. | .. |
| Light heavyweight | 1.023 (0.67–1.57) | 0.92 | .. | .. |
| Heavyweight | 0.65 (0.48–0.89) | 0.007 | .. | .. |
| Number of Rounds | 1.13 (1.10–1.15) | <0.0001 | 1.12 (1.09–1.14) | <0.0001 |
| Winning | 0.48 (0.41–0.56) | <0.0001 | 0.49 (0.42–0.59) | <0.0001 |
| Losing | 2.09 (1.79–2.44) | <0.0001 | 2.03 (1.69–2.40) | <0.0001 |
| Type of Win b | ||||
| KO | 0.37 (0.25–0.54) | <0.0001 | .. | .. |
| TKO | 0.72 (0.60–0.86) | <0.0001 | .. | .. |
| Majority decision | 1.19 (0.86–1.64) | 0.31 | .. | .. |
| Split decision | 1.33 (0.96–1.86) | .. | .. | |
| Draw | 0.81 (0.55–1.20) | 0.29 | .. | .. |
| No decision | 1.63 (0.96–2.76) | 0.07 | .. | .. |
| No contest | 1.79 (0.61–5.24) | 0.29 | .. | .. |
| Disqualified | 1.56 (0.65–3.71) | 0.32 | .. | .. |
| Referee (avg.) | 1.09 (0.51–3.45) | 0.59 | .. | .. |
| MMA Competitor characteristics (Eye Trauma Model) | ||||
| Age, years | 1.033 (1.007–1.060) | 0.01 | 1.023 (0.996–1.050) | 0.09 |
| Sex | ||||
| Female | 0.46 (0.27–0.78) | 0.004 | 0.47 (0.27–0.80) | 0.005 |
| Male | 2.18 (1.29–3.70) | 0.004 | 2.13 (1.25–3.70) | 0.005 |
| Predicted race or ethnic group | ||||
| Asian | 0.91 (0.41–2.05) | 0.83 | 0.96 (0.43–2.16) | 0.92 |
| Black | 1.55 (0.79–3.07) | 0.21 | 1.62 (0.80–3.26) | 0.18 |
| Hispanic or Latino | 1.02 (0.71–1.46) | 0.91 | 1.06 (0.74–1.52) | 0.75 |
| White | 0.89 (0.63–1.27) | 0.53 | 0.85 (0.60–1.21) | 0.36 |
| Weight, pounds | 1.003 (1.001–1.005) | 0.02 | 1.002 (1.000–1.005) | 0.09 |
| Weight class a | ||||
| Strawweight | 0.84 (0.61–1.19) | 0.33 | .. | .. |
| Flyweight | 0.91 (0.32–0.99) | 0.05 | .. | .. |
| Featherweight | .. | .. | .. | .. |
| Lightweight | 1.07 (0.50–1.20) | 0.71 | .. | .. |
| Welterweight | 0.53 (0.58–1.20) | 0.15 | .. | .. |
| Middleweight | 0.85 (0.75–1.54) | 0.85 | .. | .. |
| Light heavyweight | 0.77 (0.21–1.02) | 0.25 | .. | .. |
| Heavyweight | 0.46 (0.60–1.38) | 0.06 | .. | .. |
| Number of Rounds | 1.36 (1.24–1.48) | <0.0001 | 1.37 (1.25–1.50) | <0.0001 |
| Winning | 0.56 (0.45–0.69) | <0.0001 | 0.56 (0.45–0.70) | <0.0001 |
| Losing | 1.80 (1.44–2.25) | <0.0001 | 1.79 (1.43–2.23) | <0.0001 |
| Type of Win b | ||||
| KO | 0.45 (0.23–0.89) | 0.02 | .. | .. |
| TKO | 0.80 (0.62–1.04) | 0.09 | .. | .. |
| Tap out | 0.41 (0.29–0.56) | <0.0001 | .. | .. |
| Majority decision | 0.85 (0.42–1.72) | 0.66 | .. | .. |
| Split decision | 1.00 (0.66–1.51) | 0.99 | .. | .. |
| Draw | 0.45 (0.04–1.98) | 0.20 | .. | .. |
| No decision | 1.75 (0.60–5.12) | 0.31 | .. | .. |
| No contest | .. | .. | .. | .. |
| Disqualified | .. | .. | .. | .. |
| Referee (avg.) | 1.28 (0.40–5.64) | 0.50 | .. | .. |
OR = odds-ratios (95% CI) from univariate and multivariate logistic regression.
Reference weight class category is the bantamweight division
Reference type of win is unanimous decision
OR > 1 indicates increased risk of injury, < 1 indicates decreased risk; significant OR (p <0.05) indicated in bold
Table 3. Odds of face injury associated with risk factors in boxing and mixed martial arts competitors.*.
| Univariate OR (95% CI) | p value | Multivariate OR (95% CI) | p value | |||||
|---|---|---|---|---|---|---|---|---|
| Boxing competitor characteristics (Face Trauma Model) | ||||||||
| Age, years | 1.06 (1.04–1.08) | <0.0001 | 1.05 (1.02–1.07) | <0.0001 | ||||
| Sex | ||||||||
| Female | 0.66 (0.43–1.01) | 0.06 | 0.61 (0.40–0.94) | 0.02 | ||||
| Male | 1.52 (0.99–2.33) | 0.06 | 1.64 (1.06–2.50) | 0.02 | ||||
| Predicted race or ethnic group | ||||||||
| Asian | 0.96 (0.37–2.48) | 0.93 | 0.99 (0.39–2.54) | 0.98 | ||||
| Black | 1.08 (0.63–1.88) | 0.77 | 1.02 (0.59–1.79) | 0.94 | ||||
| Hispanic or Latino | 0.85 (0.68–1.08) | 0.18 | 0.89 (0.70–1.12) | 0.32 | ||||
| White | 1.24 (0.92–1.66) | 0.15 | 1.18 (0.88–1.58) | 0.28 | ||||
| Weight, pounds | 0.998 (0.995–1.001) | 0.20 | 0.996 (0.993–0.999) | 0.02 | ||||
| Weight class a | ||||||||
| Strawweight | 1.32 (0.52–3.34) | 0.56 | .. | .. | ||||
| Flyweight | 1.97 (0.99–3.90) | 0.05 | .. | .. | ||||
| Bantamweight | 1.17 (0.76–1.79) | 0.47 | .. | .. | ||||
| Featherweight | 1.15 (0.81–1.61) | 0.44 | .. | .. | ||||
| Lightweight | 1.40 (0.97–2.02) | 0.07 | .. | .. | ||||
| Middleweight | 1.10 (0.79–1.53) | 0.57 | .. | .. | ||||
| Cruiserweight | 0.84 (0.48–1.47) | 0.53 | .. | .. | ||||
| Light heavyweight | 0.89 (0.48–1.64) | 0.70 | .. | .. | ||||
| Heavyweight | 1.05 (0.73–1.52) | 0.80 | .. | .. | ||||
| Number of Rounds | 1.36 (1.24–1.48) | <0.0001 | 1.04 (1.01–1.07) | 0.008 | ||||
| Winning | 0.34 (0.27–0.43) | <0.0001 | 0.36 (0.29–0.46) | <0.0001 | ||||
| Losing | 2.94 (2.34–3.70) | <0.0001 | 2.78 (2.18–3.46) | <0.0001 | ||||
| Type of Win b | ||||||||
| KO | 0.85 (0.57–1.26) | 0.41 | .. | .. | ||||
| TKO | 1.06 (0.84–1.33) | 0.63 | .. | .. | ||||
| Majority decision | 0.68 (0.39–1.19) | 0.17 | .. | .. | ||||
| Split decision | 1.24 (0.79–1.97) | 0.35 | .. | .. | ||||
| Draw | 1.04 (0.64–1.69) | 0.89 | .. | .. | ||||
| No decision | 1.67 (0.83–3.36) | 0.15 | .. | .. | ||||
| No contest | 0.82 (0.11–6.11) | 0.85 | .. | .. | ||||
| Disqualified | 2.06 (0.73–5.83) | 0.17 | .. | .. | ||||
| Referee (avg.) | 1.38 (0.48–7.19) | 0.82 | .. | .. | ||||
| MMA Competitor characteristics (Face Trauma Model) | ||||||||
| Age, years | 1.03 (1.01–1.05) | 0.02 | 1.02 (1.00–1.04) | 0.14 | ||||
| Sex | ||||||||
| Female | 0.63 (0.42–0.95) | 0.03 | 0.67 (0.44–1.02) | 0.06 | ||||
| Male | 1.59 (1.05–2.40) | 0.03 | 1.49 (0.98–2.27) | 0.06 | ||||
| Predicted race or ethnicity | ||||||||
| Asian | 0.99 (0.48–2.02) | 0.98 | 1.00 (0.49–2.05) | 0.99 | ||||
| Black | 1.29 (0.68–2.44) | 0.43 | 1.35 (0.70–2.59) | 0.37 | ||||
| Hispanic or Latino | 0.95 (0.68–1.32) | 0.77 | 0.99 (0.71–1.38) | 0.95 | ||||
| White | 1.00 (0.72–1.37) | 0.98 | 0.95 (0.69–1.32) | 0.76 | ||||
| Weight, pounds | 1.002 (1.000–1.003) | 0.10 | 1.001 (0.999–1.003) | 0.30 | ||||
| Weight class a | ||||||||
| Strawweight | 1.26 (0.91–1.75) | 0.16 | .. | .. | ||||
| Flyweight | 1.36 (0.94–1.97) | 0.10 | .. | .. | ||||
| Featherweight | 0.81 (0.94–1.97) | 0.30 | .. | .. | ||||
| Lightweight | 1.12 (0.78–1.60) | 0.54 | .. | .. | ||||
| Welterweight | 0.17 (0.04–0.71) | 0.01 | .. | .. | ||||
| Middleweight | 1.16 (0.85–1.58) | 0.37 | .. | .. | ||||
| Light heavyweight | 1.18 (0.81–1.74) | 0.39 | .. | .. | ||||
| Heavyweight | 0.82 (0.44–1.52) | 0.52 | .. | .. | ||||
| Number of Rounds | 1.22 (1.13–1.33) | <0.0001 | 1.23 (1.13–1.35) | <0.0001 | ||||
| Winning | 0.37 (0.29–0.45) | <0.0001 | 0.37 (0.30–0.46) | <0.0001 | ||||
| Losing | 2.74 (2.22–3.40) | <0.0001 | 2.70 (2.17–3.33) | <0.0001 | ||||
| Type of Win b | ||||||||
| KO | 0.91 (0.55–1.51) | 0.72 | .. | .. | ||||
| TKO | 1.14 (0.90–1.44) | 0.28 | .. | .. | ||||
| Tap out | 0.40 (0.30–0.55) | <0.0001 | .. | .. | ||||
| Majority decision | 0.69 (0.33–1.44) | 0.32 | .. | .. | ||||
| Split decision | 0.95 (0.63–1.43) | 0.81 | .. | .. | ||||
| Draw | 0.51 (0.12–2.13) | 0.36 | .. | .. | ||||
| No decision | 1.16 (0.35–3.89) | 0.81 | .. | .. | ||||
| No contest | .. | .. | .. | .. | ||||
| Disqualified | 2.90 (1.15–7.33) | 0.02 | .. | .. | ||||
| Referee (avg.) | 1.25 (0.48–4.69) | 0.38 | .. | .. | ||||
OR = odds-ratios (95% CI) from univariate and multivariate logistic regression.
Reference weight class category is the bantamweight division
Reference type of win is unanimous decision
OR > 1 indicates increased risk of injury, < 1 indicates decreased risk; significant OR (p <0.05) indicated in bold
In the boxing and MMA multivariate models, the contestant gender, number of rounds, and winning or losing the fight were significant variables in assessing risk for eye and face injuries but not body trauma. Race or ethnicity had no effect on risk of eye, face, and body injuries. Age and weight had minimal effects on odds of eye, face, and body trauma (Table 2, Table 3).
Discussion
Injuries are common in combat sports. Given the style of MMA fighting, an increased risk of bodily injury has been a concern and several studies have shown an increased injury rate overall in MMA fighting. Our study shows injuries occur in over half of MMA fights (53.33%) and over a third of boxing matches (35.68%). Another study out of Edmonton, Canada21 used post-fight medical data between 2000 and 2013 and found that MMA fighters also were more likely to experience injury than boxers (59.4% vs 49.8%, p<0.001), but in this group both boxers and MMA fighters experienced injury at an even higher rate compared to our study. Blesdoe found 17.1 injuries per 100 fight participations in boxing and 28.6 injuries per 100 fight participations in MMA using the Nevada data in the early 2000s,22,23 which are similar rates to our study that included data up to 2020. Although grappling combat sports, such as wrestling, have shown a much lower injury rate,24 striking combat sports, such as boxing and MMA, are somewhat comparable in their higher overall injury rate.22,23
Although injuries were more prevalent in MMA fights, eye trauma was more common in boxing. Eye trauma represented 47.63% of injuries in boxing, while 25.59% in MMA. MMA may look more brutal on observation, but boxing targets the head and upper body only with no blows allowed below the belt. Boxers sustain constant powerful punches to the head over a potential 36-minute period, which likely contributes to the higher rate of periocular or eye trauma. Boxers in our study also experienced a higher percentage of head blow injuries compared to MMA (24.94% vs 6.94%, p<0.0001). Just the sheer number of blows to the head likely increases the risk of eye trauma in boxers. Karpman et al21 also found that boxers were more likely to suffer serious eye injury, such as retinal detachment or corneal abrasion, than MMA fighters (1.1% vs 0.3%, p=0.02). However, only retinal detachment and corneal abrasion were listed in this study and other periocular, ocular, or orbital trauma was not specified, and we do not know long term effects of these injuries.
Although eye trauma overall was higher in boxing, orbital fractures were sustained at a higher percentage in MMA than in boxing (17.62% vs 3.14%, p<0.0001). This may be due to the different type of hits allowed to the head (kick, knee, or punch). It may also be related to the differences in the types of gloves used between the two combat sports, with boxing gloves having more padding and MMA gloves having less padding with exposed fingers and palms for use in grappling. In addition to potentially affecting the athletes immediate fighting ability, orbital fractures can affect the athlete’s ability to return to the ring. One study showed that orbital fractures were a cause of pre-bout cancellation due to chronic orbital fracture with fat prolapse seen on CT imaging.25 Visual compromise or persistent diplopia could also factor into an athletes ability to fight.
Of all the eye and periocular injuries, eyelid and eyebrow lacerations make up the majority of injuries in both boxing and MMA. They made up 81.31% of eye injuries in boxing and 67.21% of eye injuries in MMA. Ngai and Hsu26 looked at MMA only data from the Nevada Athletic Commission from 2002 to 2007 and also found lacerations to make up the majority of injuries overall at 17.3% and ocular injury at 5.4%. Location of lacerations were not specified though and ocular injury was not defined in detail, including how it was defined and searched for in the available online data. Zazryn et al27 showed that 19% of all injuries in boxing training and professional matches were lacerations in the brow region. Although these injuries may seem minor compared to a fracture or concussion, periocular lacerations can be quite troublesome to fighters. Fighters can suffer from repeat lacerations or wound reopening in the same area affecting future fights. Lacerations can also obscure vision and affect contestants’ ability to fight, which can lead to more severe injuries or loss of the fight. Periocular lacerations were the cause of referee or ringside physician stoppage in 3.1 (+/− 1.3) % of matches in one study that evaluated 642 consecutive publicly televised MMA matches from 1993 to 2003.28 Even so, many fights do continue to the end or for some time before stoppage when a periocular laceration is present. For example, in the Nate Diaz versus Jorge Masvidal fight in Madison Square Garden in 2019, Nate Diaz suffered a right eyebrow laceration in the first round. It wasn’t until the 3rd round at 5 minutes (end of the round), after the lacerated brow was obstructing Diaz’s vision, that the ringside doctor ruled that Diaz could not continue into the 4th round. Post-fight, there was media backlash against the ringside physician for stopping the fight, even though calls like this are made to protect the athletes.
It is difficult to determine the rate of serious eye injuries from the Nevada data. Serious eye injuries would include injuries with lasting vision loss or injuries that cause enough vision loss or damage to result in the inability to fight. In our study, retina injuries were noted in 2–3% of eye injuries in both sports and glaucoma in 3.27% of boxing eye injuries, which could result in vision loss even if not occurring immediately during the athletes active fighting career. Serious eye injuries are definitely known to happen and have been discussed in the media. Cody Stevens suffered a ruptured globe in his MMA fight against Aaron Mitchell in Cleveland, OH in 2018 after a poke to the eye. Ruptured globes have also been reported in boxing related injuries.29 Cat Zingano suffered a toe to the eye from a head kick in a 2018 MMA match resulting in damage to the iris, retina, and an intraocular hemorrhage. Ultimately Zingano appealed to the California State Athletic Commission to provide clarity on rules concerning eye pokes and retired from fighting. Michael Bisping suffered a head kick in 2013 that resulted in a retinal detachment, which ultimately resulted in enucleation later that year. He then continued to compete even though he was monocular until he started having issues with his good eye following a fight in 2017, after which he retired. Retinal detachments have also been reported in boxing9–13 along with intraocular damage that could result in acute or delayed vision loss.9 Giovinazzo et al found that 58% of boxers had damage to the angle, lens, macula, or peripheral retina that could have long term visual consequences.9 Unfortunately post-fight ophthalmic examination data or long-term follow up data is not available on the Nevada Athletic Commission website or in other sources. Intraocular injuries suffered during a match can have long-term, vision-threatening repercussions well-after the match that are unknown from the current available data. Additional pre- and post-fight eye examination details and follow up data on all of these athletes and especially those that were noted to have eye injuries or who were referred for an eye evaluation would be needed for MMA and boxing to clearly determine the rate of serious vision-threatening eye injury. Likely it is higher than found in this study, which reports only acute eye injuries and does not have follow up or classify serious eye injury.
A greater number of MMA fighters in our study, compared to boxers, needed clearance by an eye doctor before the next match. This could mean that eye injuries in MMA had greater sub-acute or chronic ramifications, such as glaucoma or retinal detachment, that required further work up outside of the ringside physician. A greater number of ophthalmology referrals were placed for boxing, particularly with a higher number of glaucoma referrals, perhaps due to a greater incidence of hyphema or angle injury. Again, we do not have detailed information regarding these referrals or clearance examinations, so it is likely that the rate of serious eye injury is higher in these athletes than available in the Nevada data.
In our univariate regression models, age, male gender, increased number of rounds, and being the losing fighter increased the odds of eye and face injury, whereas fights that ended in KO, TKO, or tap out actually lowered the odds. Number of rounds was also a significant variable in our multivariate models assessing risk of eye and face injury. This may be a good sign that fights that end earlier lead to less trauma, whether the fight is stopped by the athlete or the referee. Therefore, it is of critical importance for referees and ringside physicians to have clear guidelines pertaining to calling the fight for the protection of the athletes, and for athletes to be educated about when to tap out to protect themselves from serious injury.
Women’s participation in MMA came later and took almost two decades to have its first main stage event with the UFC in 2013, Ronda Rousey vs. Liz Carmouche. Perceptions of gender and social roles have affected marketing of female MMA fights30 and some viewers’ ability to accept women participating in such a violent sport. However, Women’s MMA has grown in popularity significantly since that first UFC fight with over one hundred active female UFC fighters under four different weight classes and millions of fans watching Women’s UFC fights.31 In our study, female contestants were found to have significantly lower odds of eye, face, and body injuries in MMA and decreased odds for eye injury in boxing compared to male contestants. It is unknown as to why women are at significantly lower odds for certain injuries in both MMA or boxing, but gender biases may be playing a role. If violence is less accepted in female fights, referees or physicians may stop the fight sooner and the audience may encourage this as well. Alternatively, more violent, gruesome fights may be encouraged in male fights. Additional evaluation would be necessary to determine the cause for this finding though. In addition to gender, we analyzed whether race and ethnicity had any association with higher or lower odds of injury. We felt it important to evaluate race and ethnicity to see if there was a trend for more injuries in certain groups, which may signify bias at some level of the fight – either at referee or physician level, or elsewhere as has been noted in other professional sports.32 Our evaluation of the Nevada Athletic Commission contests found that race and ethnicity did not have a significant association with injuries which hopefully signifies that potential biases that could affect injury rates are either limited or don’t play a role in this dataset. A limitation is that validation of our program that determined race/ethnicity noted 75–80% agreement. Therefore, we very well could be missing some bias based on incorrectly labeled race/ethnicity by our program.
An additional limitation of our study is the unknown information of the type, quality, and training of the ringside physicians at each of the matches in both sports. The ringside physician determines the medical stability of the participants through pre-fight physicals, monitors and evaluates participants during contests, and confers with the referee when necessary. Then they conduct post-fight physicals, document injuries, make recommendations for further evaluation, examination or clearance, and administer emergency assistance to the contestants until emergency medical personnel assume responsibility. Differences in type, quality, and training in ringside physicians between the two sports could affect the clinical assessments, diagnoses given and documented, and referrals recommended. The ringside physician is required to have an MD or DO, active license in Nevada for a minimum of 5 years, and board certification in their specialty (https://boxing.nv.gov/Licensing/License_Official/). The specialties vary though and include emergency medicine, anesthesiology, neurology, etc. A physician’s experience with ophthalmic and ocular trauma evaluation likely varies which would play a role in the number of referrals or diagnoses noted in the ringside report. These differences likely affected our results since the data is based on the ringside physician report. Documentation of findings from a standardized ophthalmic examination by a trained ophthalmologist after each match would likely yield more ocular findings and higher rates of eye injury. Our study is also limited in accounting for chronic or pre-existing injuries such as periocular lacerations that may increase the risk for future injuries given the limitations of the dataset. Chronic conditions, such as glaucoma, also cannot be followed or evaluated with the available data on the website either.
The Association of Ringside Physicians have made some recommendations including annual dilated eye examination, minimum uncorrected visual acuity of 20/200 in each eye, minimum corrected visual acuity of 20/60 in each eye, absence of major ocular disease, monocular contestants not allowed to compete, notification of ocular risk with high myopia, previous eye surgery including LASIK or PRK, and clearance from the ringside physician and an ophthalmologist for those with a history of eye surgery such as cataract or retinal detachment. However, these are just recommendations and not absolute requirements, and therefore contestants will still fight visually impaired or at higher risk for eye injury. These standard visual requirements should be strictly enforced for a fighter to be eligible. Based on our study, one way to prevent eye or other trauma could be to decrease the number of rounds in both sports. Given that eye injuries are higher in boxing and they often have more rounds, decreasing rounds and therefore time in the ring could prevent eye trauma. In boxing, it was common through the early 20th century for fights to have unlimited rounds. Then for decades boxing matches were 15 rounds and it wasn’t until one fighter died in 1982 in the 14th round of a nationally broadcasted championship fight, that the World Boxing Council converted to a maximum of 12 rounds in professional boxing. In the future, the number of rounds may need to be decreased furthermore to protect these athletes. Given that eye injuries were such a large percentage of injuries in boxing, a ringside ophthalmologist may also be an important factor for the safety of boxers and should be considered in MMA. Other recommendations include serious consideration of stoppage with periocular or eye injuries that cause decreased vision or obscuration of vision, such as large eyelid or periocular lacerations or hematomas. Although there are fouls regarding eye gouging, harsher punishment for eye pokes or hits may help prevent serious eye trauma. Protective equipment may also be the answer in the future even though it could change the nature of the game in combat sports. Studies would need to be conducted to determine if additional or different protective gear can prevent specific types of eye injury.
In summary, our study found that MMA had a greater prevalence of all injuries, whereas boxing had more eye trauma. MMA fighters more frequently required clearance by an ophthalmologist before their next fight, suggesting the possibility for more severe eye injury. A significant risk factor for eye and face injury was the number of rounds with fights ending prematurely conveying a lower risk. Further studies are needed with detailed documentation of the eye injuries and long term follow up to truly know the extent of eye trauma in combat sports, the impact of eye trauma and its effects on vision long term, and ways to prevent or decrease its incidence in combat sports.
Supplementary Material
Table 3. Odds of body injury associated with risk factors in boxing and mixed martial arts competitors.*.
| Univariate OR (95% CI) | p value | Multivariate OR (95% CI) | p value | |
|---|---|---|---|---|
| Boxing competitor characteristics (Body Trauma Model) | ||||
| Age, years | 1.01 (0.99–1.03) | 0.33 | 1.01 (0.99–1.03) | 0.47 |
| Sex | ||||
| Female | 0.92 (0.62–1.36) | 0.68 | 0.97 (0.65–1.44) | 0.87 |
| Male | 1.09 (0.73–1.61) | 0.68 | 1.03 (0.69–1.54) | 0.87 |
| Predicted race or ethnic group | ||||
| Asian | 1.74 (0.76–4.02) | 0.19 | 1.76 (0.76–4.08) | 0.19 |
| Black | 0.60 (0.31–1.14) | 0.12 | 0.60 (0.31–1.14) | 0.12 |
| Hispanic or Latino | 1.19 (0.94–1.52) | 0.15 | 1.19 (0.93–1.51) | 0.17 |
| White | 0.80 (0.58–1.09) | 0.15 | 0.80 (0.59–1.10) | 0.17 |
| Weight, pounds | 1.00 (0.99–1.00) | 0.84 | 1.00 (0.99–1.00) | 0.60 |
| Weight class a | ||||
| Strawweight | 0.47 (0.11–1.94) | 0.30 | .. | .. |
| Flyweight | 1.05 (0.45–2.45) | 0.91 | .. | .. |
| Bantamweight | 0.71 (0.43–1.15) | 0.16 | .. | .. |
| Featherweight | 1.02 (0.72–1.43) | 0.93 | .. | .. |
| Lightweight | 0.83 (0.55–1.26) | 0.38 | .. | .. |
| Middleweight | 0.85 (0.61–1.20) | 0.36 | .. | .. |
| Cruiserweight | 1.09 (0.67–1.78) | 0.72 | .. | .. |
| Light heavyweight | 1.25 (0.74–2.10) | 0.41 | .. | .. |
| Heavyweight | 0.92 (0.64–1.33) | 0.66 | .. | .. |
| Number of Rounds | 1.11 (1.08–1.14) | <0.0001 | 1.11 (1.07–1.14) | <0.0001 |
| Winning | 1.48 (1.20–1.82) | <0.0001 | 1.50 (1.21–1.86) | <0.0001 |
| Losing | 0.68 (0.55–0.83) | <0.0001 | 0.67 (0.54–0.83) | <0.0001 |
| Type of Win b | ||||
| KO | 0.39 (0.24–0.65) | <0.0001 | .. | .. |
| TKO | 0.73 (0.58–0.93) | 0.009 | .. | .. |
| Majority decision | 0.62 (0.37–1.07) | 0.09 | .. | .. |
| Split decision | 1.32 (0.87–2.01) | 0.19 | .. | .. |
| Draw | 0.41 (0.21–0.81) | 0.01 | .. | .. |
| No decision | 0.61 (0.22–1.66) | 0.33 | .. | .. |
| No contest | .. | .. | .. | .. |
| Disqualified | 0.41 (0.06–2.99) | 0.38 | .. | .. |
| Referee (avg.) | 1.31 (0.52–4.82) | 0.71 | .. | .. |
| MMA competitor characteristics (Body Trauma Model) | ||||
| Age, years | 1.024 (1.003–1.047) | 0.03 | 1.024 (1.002–1.047) | 0.03 |
| Sex | ||||
| Female | 0.69 (0.48–0.99) | 0.04 | 0.66 (0.45–0.96) | 0.03 |
| Male | 1.45 (1.01–2.09) | 0.04 | 1.52 (1.04–2.22) | 0.03 |
| Predicted race or ethnicity | ||||
| Asian | 1.14 (0.60–2.14) | 0.69 | 1.18 (0.62–2.21) | 0.62 |
| Black | 0.66 (0.35–1.24) | 0.20 | 0.64 (0.33–1.21) | 0.17 |
| Hispanic or Latino | 1.11 (0.83–1.49) | 0.48 | 1.12 (0.84–1.50) | 0.45 |
| White | 0.98 (0.73–1.31) | 0.88 | 0.97 (0.72–1.30) | 0.83 |
| Weight, pounds | 1.000 (0.998–1.002) | 0.78 | 1.000 (0.997–1.002) | 0.84 |
| Weight class a | ||||
| Strawweight | 0.91 (0.67–1.25) | 0.57 | .. | .. |
| Flyweight | 1.13 (0.79–1.59) | 0.51 | .. | .. |
| Featherweight | 0.97 (0.69–1.37) | 0.86 | .. | .. |
| Lightweight | 1.06 (0.77–1.47) | 0.73 | .. | .. |
| Welterweight | 0.85 (0.45–1.58) | 0.60 | .. | .. |
| Middleweight | 1.04 (0.78–1.38) | 0.79 | .. | .. |
| Light heavyweight | 1.11 (0.78–1.57) | 0.57 | .. | .. |
| Heavyweight | 0.84 (0.49–1.46) | 0.54 | .. | .. |
| Number of Rounds | 1.23 (1.14–1.33) | <0.0001 | 1.23 (1.14–1.33) | <0.0001 |
| Winning | 1.03 (0.86–1.23) | 0.73 | 1.05 (0.88–1.25) | 0.61 |
| Losing | 0.97 (0.81–1.16) | 0.73 | 0.95 (0.80–1.14) | 0.61 |
| Type of Win b | ||||
| KO | 0.66 (0.40–1.08) | 0.10 | .. | .. |
| TKO | 0.66 (0.52–0.83) | <0.0001 | .. | .. |
| Tap out | 0.63 (0.50–0.80) | <0.0001 | .. | .. |
| Majority decision | 0.30 (0.12–0.75) | 0.01 | .. | .. |
| Split decision | 1.01 (0.72–1.44) | 0.94 | .. | .. |
| Draw | 0.99 (0.39–2.57) | 0.99 | .. | .. |
| No decision | 0.54 (0.13–2.27) | 0.40 | .. | .. |
| No contest | 0.99 (0.12–8.12) | 0.99 | .. | .. |
| Disqualified | 0.91 (0.27–3.05) | 0.88 | .. | .. |
| Referee (avg.) | 1.14 (0.44–4.05) | 0.47 | .. | .. |
OR = odds-ratios (95% CI) from univariate and multivariate logistic regression.
Reference weight class category is the bantamweight division
Reference type of win is unanimous decision
OR > 1 indicates increased risk of injury, < 1 indicates decreased risk; significant OR (p <0.05) indicated in bold
Financial support:
This research was supported, in part, by the UCSF Vision Shared Resource Core Grant (NIH/NEI P30 EY002162) and an unrestricted grant from Research to Prevent Blindness to the Department of Ophthalmology at UCSF.
Footnotes
None of the authors have any conflicts of interest or financial disclosures.
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