Blood Biomarkers Reveal Repetitive Head Injury in MMA Fighters

Megan Brooks

July 18, 2017

Concentrations of neurofilament light (NFL) chain and tau in blood are elevated in professional mixed martial arts (MMA) fighters who are exposed to repetitive head trauma, new research shows.

NFL and tau are both markers of brain injury. NFL levels in blood appear more tightly linked to acute traumatic brain injury, whereas tau may be a better measure of cumulative damage over time, the researchers report.

Charles Bernick, MD, from the Cleveland Clinic Lou Ruvo Center for Brain Health in Las Vegas, Nevada, presented the study in a poster session July 14 at the American Academy of Neurology (AAN) 2017 Sports Concussion Conference in Jacksonville, Florida.

This study is part of the larger ongoing Professional Fighters Brain Health study designed to detect "not just individual concussions but permanent brain injury overall at its earliest stages and to determine which fighters are at greatest risk of long-term complications," Dr Bernick explains in a conference statement.

"Our study looked at data over a 5-year period and found elevated levels of two brain injury markers in the blood. Now the question is whether they may signify permanent traumatic brain injury with long-term consequences," he said.

Participants in the study included 291 active professional fighters (128 boxers, 163 MMA fighters; mean age, 29.9 years), 44 retired fighters (38 boxers, 6 MMA fighters; mean age, 45.3 years) and 103 controls (mean age, 29.58 years) who participate in the Professional Fighters Brain Health Study.

"We were able to look at the levels of NFL and tau in the blood on a yearly basis and correlate them with other things we have available in the study," Dr Bernick told Medscape Medical News.

They found that active professional fighters had higher NFL and tau levels than did retired fighters or controls (P < .0001).

Concentrations of NFL, but not tau, correlated with the amount of self-reported sparring in the 2 weeks before baseline. Neither NFL nor tau levels were associated with age or ethnicity in any of the groups or number of professional fights in the active fighters.  Higher NFL levels correlated with lower performance on computerized tests of processing speed.

Dr Bernick noted that while NFL levels were higher in active fighters at the start of the study, the levels did not increase significantly during the study period. On the other hand, there was a group of fighters who showed increasing levels of tau over time; this subgroup had a 7% decline in the volume of their thalamus.

"This is kind of intriguing," Dr Bernick said. "With tau levels, this correlation with thalamic volume raises the question whether we could measure tau overtime in active athletes or military and could that be an indicator of accumulating brain injury. We don't know that yet," he said.

A limitation of the study was the difference in the average age of active and retired fighters.

"More research needs to be done to see how these may be used to monitor traumatic brain injury and the neurological consequences over time," said Dr Bernick.

Cyrus Raji, MD, PhD, from the University of California, San Francisco, agrees. 

"The results of this study are useful in identifying potential blood-based biomarkers for head trauma. Future studies can examine how these markers change management and outcomes," said Dr Raji, who wasn't involved in the study.

The study was supported by the University of California, Los Angeles Dream Fund, Ultimate Fighting Championship (UFC), Bellator Mixed Martial Arts (MMA), Haymon Boxing, and Top Rank. The authors have disclosed no relevant financial relationships.

American Academy of Neurology (AAN) 2017 Sports Concussion Conference. Presented July 14, 2017.

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