Sex Moderates the Relationship That Number of Professional Fights Has With Cognition and Brain Volumes

Longitudinal Changes in Cognitive Functioning and Brain Structure in Professional Boxers and Mixed Martial Artists After They Stop Fighting

BACKGROUND AND OBJECTIVES

This study compares longitudinal changes in cognitive functioning and brain structures in male fighters who transitioned to an inactive fighting status without any further exposure to repetitive head impacts (RHIs) and fighters remaining active with continual exposure to RHIs.

METHODS

Participants were recruited from the Professional Fighters Brain Health Study. At time point (TP)1, all fighters were active, with continual exposure to RHIs. At TP2, fighters were considered "transitioned" if they had no sanctioned professional fights and had not been sparring for the past 2 years. Fighters were considered "active" if they continued to train and compete. All fighters underwent cognitive testing and 3T MRI at both TPs. A subset of our fighters (50%) underwent blood sampling for the characterization of neurofilament light (NfL) levels at both TPs. Linear mixed-effect models were applied to investigate the potentially different longitudinal trajectories (interaction effect between group and time) of cognitive function measures, NfL levels, and regional thickness measures (derived from structural MRI) between transitioned and active fighters.

RESULTS

Forty-five male transitioned fighters (aged 31.69 ± 6.27 years [TP1]; 22 boxers, 22 mixed martial artists, and 1 martial artist) and 45 demographically matched male active fighters (aged 30.24 ± 5.44 years [TP1]; 17 boxers, 27 mixed martial artists, and 1 martial artist) were included in the analyses. Significantly different longitudinal trajectories between transitioned and active fighters were observed in verbal memory (p FDR = 4.73E-04), psychomotor speed (p FDR = 4.73E-04), processing speed (p FDR = 3.90E-02), and NfL levels (p = 0.02). Transitioned fighters demonstrated longitudinally improved cognitive functioning and decreased NfL levels, and active fighters demonstrated declines in cognitive performance and stable NfL levels. Of 68 cortical regions inspected, 54 regions demonstrated a consistently changing trajectory, with thickness measures stabilizing on a group level for transitioned fighters and subtly declining over time for active fighters.

DISCUSSION

After fighters' cessation of RHI exposure, cognitive function and brain thickness measures may stabilize and blood NfL levels may decline. This study could be a starting point to identify potential predictors of individuals who are at a higher risk of RHI-related long-term neurologic conditions.

Head Trauma Exposure in Mixed Martial Arts

Combat sports training involves a high risk of head injury. Previously published research on head trauma exposure in MMA evaluated only the knockouts (KO), without calculating all head strikes. The aim of the research was to evaluate the total head trauma exposure during MMA competitions among male and female fighters. Two thousand four hundred and eighty-eight MMA fights from all numbered UFC events between 2000 and 2021 were analyzed. A database containing the results from officially published scorecards with information such as the outcome of a fight, its duration, number of strikes (significant and total amount of hits) depending on location and knockdowns was created. Additional video verification of the knockout technique was carried out. The athletes received an average of 2.41 significant head strikes out of a total of 6.30 head strikes per minute. Head strikes were more common in female fights than in male. Women executed more total and significant head strikes per minute than men. Head trauma caused the ending of 31.6% of all fights-more often in male fights (32.2%) than female (23.1%). It was the most common cause of knockouts-88.1%. Professional fights in mixed martial arts involve high exposure to head trauma. A careful evaluation of the risk involved in training in such a discipline is necessary to provide adequate prevention methods.

A brief descriptive outline of the rules of mixed martial arts and concussion in mixed martial arts

Mixed martial arts (MMA), a combat sport consisting of wrestling, box-ing, and martial arts, is a popular activity associated with danger and vi-olence. Of concern are the repetitive head impacts, both subconcussive and concussive, sustained by MMA athletes. The rules of MMA en-courage head strikes, but there was no formal concussion protocol in the Ultimate Fighting Championship (UFC) until 2021. Because the UFC was established less than 30 years, the long-term consequences of these repetitive concussive head blows are lacking. In this review, we focus on current literature sought to summarize the current knowledge of repetitive head impacts and concussions in MMA. The objectives were to outline (a) the rules of MMA; (b) the postconcussion protocol for UFC athletes; (c) current behavioral and biochemical diagnostic measures; (d) epidemiology and prevalence of concussion in MMA; (e) long-term effects of subconcussive repetitive head impacts; (f) biome-chanics of head impacts; and (g) considerations and research topics that warrant future research.