JACKSONVILLE, Fla. (CBS) — The result of the clash between undefeated, legendary boxer Floyd Mayweather and prize-mixed martial artist Conor McGregor is no longer in question. However, these combatants of the squared circle and the octagon may share a major debilitating, internal challenge, according to a study.

Boxers and mixed martial arts fighters are potentially showing signs of long-term brain injury in their blood, per a study presented at the American Academy of Neurology’s Sports Concussion Conference.

“This study is part of a larger study 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,” said study author Charles Bernick, MD, of the Cleveland Clinic Lou Ruvo Center for Brain Health in Las Vegas and member of the American Academy of Neurology. “Our study looked at data over a five-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.”

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Researchers got blood samples from 291 active professional fighters with an average age of 30. In addition, there were 44 retired fighters with an average age of 45 and 103 non-fighters with an average age of 30.

They collected data, ranging a five-year span and discovered elevated levels of two brain injury markers in the blood.

Researchers measured two biological markers via brain proteins called neurofilament light chain and tau. Both parts of the nerve fiber that can be detected in the blood when the fibers are injured.

Researchers found that active professional fighters had higher levels of both proteins compared to retired fighters or non-fighters. They also found that the more a fighter sparred in the two weeks before the blood samples were taken, the higher the levels of neurofilament light chain in their blood.

The study also found fighters with higher levels of neurofilament light chain protein did not do as well on computerized tests that measure the brain’s processing speed as the retired fighters and non-fighters.

The study is part of the Professional Fighters Brain Health study, which is ongoing.

The study was supported by the University of California, Los Angeles Dream Fund, Ultimate Fighting Championship, Bellator Mixed Martial Arts, Haymon Boxing and Top Rank.