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

ABSTRACT

Background

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.

Objective

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.

Methods

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.

Results

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.

Conclusion

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

Acknowledgements

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

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.

Ethics approval

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

Informed consent

Informed written consent was obtained from all participants.

Data availability statement

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

Disclosure statement

No potential conflict of interest was reported by the author(s).

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.

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.