Prior football or rugby exposure and white matter signal abnormalities in professional male mixed martial arts fighters

ABSTRACT

White matter signal abnormalities have been associated with traumatic brain injury (TBI) and repetitive head impacts (RHI) in contact sports (e.g. American football, rugby). However, previous studies of mixed martial arts (MMA) fighters from the Professional Fighters Brain Health Study have not found greater white matter signal abnormalities in fighters versus controls. This study aims to explore the varying white matter effects of football/rugby and MMA by analyzing how football/rugby history in mixed martial arts fighters may relate to white matter signal abnormalities, helping to further our understanding of sport-specific brain health risks. Baseline visits for 90 active, professional, male mixed martial arts fighters and 27 unexposed male controls were cross-sectionally analyzed. Wilcoxon and Kruskal-Wallis tests compared demographics and white matter signal abnormalities, and multivariable regression models examined the associations between football/rugby history and white matter signal abnormality burden in fighters, adjusting for age, education, race, fights, MRI scanner, and supratentorial volume. 37/90 fighters had football/rugby history (mean: 4 years; range: 1-12 years). White matter signal abnormalities were significantly greater in fighters with football/rugby history compared to fighters without football/rugby history (Wilcoxon, p = 0.0190). Football/rugby history was significantly associated with white matter signal abnormality burden > 75^th percentile (OR: 12, CI: 3.3-61, p < 0.001) and > 50^th percentile (OR: 3.2, CI: 1.2-9.4, p = 0.024) in fighters. Years of football/rugby were also significantly associated with white matter signal abnormalities. Our findings expand on previous literature by demonstrating a significant relationship between white matter signal abnormalities (WMSAs) and football/rugby history but not MMA. Furthermore, our study suggests an added risk for WMSAs in MMA fighters with a history of football/rugby. Future research should further evaluate WMSAs in contact sports, helping to inform athletes, regulatory bodies, and healthcare providers of the potential brain health risks of contact sports.

KEYWORDS:

• MMA
• Football
• Rugby
• MRI
• White matter

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Acknowledgments

The study team would like to thank Anne Reisch and Anthony Davidson for their assistance with the study.

Conflicts of Interest

Dr. Charles Bernick receives research funding support (see Funding). The remaining authors declare no relevant conflicts of interest.

Ethics Approval

Institutional Review Board/Ethics Committee approval was obtained by the institutional review board at the Cleveland Clinic.

Data Availability

Study data was collected as part of the Professional Fighters Brain Health Study; data is not publicly available.

Author Contributions

Concept and planning– Esagoff, Narapareddy, Bernick, Acquisition, analysis, and interpretation of data – Esagoff, Gifford, Luna, Sair, Shan, Bernick, Manuscript drafting and revision– Esagoff, Gifford, Raj, Luna, Sair, Peters, Narapareddy, Bernick

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/00913847.2024.2382085

Data Access, Responsibility, and Analysis

Guogen Shan and Charles B. Bernick had full access to all the data in the study and took responsibility for the integrity of the data and the accuracy of the data analysis.

Informed Consent

Informed written consent was obtained from all participants.

Additional information

Funding

This project received no direct funding. Dr. Charles Bernick receives research funding support from the Ultimate Fighting Championship, Top Rank Promotions, and Haymon Boxing.