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CTE study: 41% of fighters TES positive; age, knockouts and number of fights deemed risk factors

A recent study of 176 combat sports athletes looked into CTE risk factors

Age and the number of repeated head injuries put combat sports athletes at risk of CTE
Age and the number of repeated head injuries put combat sports athletes at risk of CTE
Photo by Stan Grossfeld/The Boston Globe via Getty Images

A recent study published in the British Journal of Sports Medicine found that two significant factors that could lend themselves to combat sports athletes developing chronic traumatic encephalopathy (CTE). Those two factors are age and the number of repeated head injuries.

The study, “Traumatic encephalopathy syndrome: application of new criteria to a cohort exposed to repetitive head impact,” looked at the characteristics of those who met the criteria for Traumatic Encephalopathy Syndrome (TES). The National Institute of Neurological Disease and Stroke (NINDS) established the TES criteria. A team of “20 expert clinician-scientists in neurology, neuropsychology, psychiatry, neurosurgery, and physical medicine and rehabilitation, from 11 academic institutions” considered 40 studies (229 cases) when developing the TES criteria.

The TES criteria are designed to represent clinical CTE. Much of the information used to develop the protocol came from studies of former professional football players. The survey of combat sports athletes applied the information gathered from the Professional Fighters Brain Health Study (PBHS) and compared it against the data collected by the analysis of the football players.

The combat sports athlete study was not large. It included 109 retired fighters and 67 who have not retired. All of the fighters in the study were 35 or older or retired. Of the group of 176 fighters, 110 were boxers and 66 were MMA fighters. The study found that seventy-two of those involved (41 percent) had TES. Further, the analysis found that those who started participating in combat sports at a younger age — in this group, that was mostly the boxers — were more likely to be categorized as TES positive. In addition, those individuals tended to have more professional fights and suffered more knockouts than the athletes who did not fall into the group with TES.

The study also found that those who were TES positive had lower regional brain volumes and lower scores on simple and choice reaction time, as well as lower psychomotor speed.

To be counted as a fighter with TES, the combat sports athlete study had certain boxes that needed to be checked. TES positive athletes had to have had substantial exposure to repeated head injuries (RHI), cognitive impairment and/or poorly regulated emotional responses, progression of symptoms and no other factors could be responsible for their symptoms.

The cutoff for RHI was 10 or more professional fights. As for cognitive impairment, the fighters were evaluated via a test that took approximately one hour to complete. The progress of the symptoms was based on comparing the tests the fighters had undergone during the PBHS. Finally, outside factors were determined through fighters self-reporting their medical history, clinical impressions and brain MRIs.

The study found that 41 percent of the fighters were TES positive. That number jumped to 60 percent for fighters older than 50. Of the individuals deemed TES positive, 83 percent were boxers and 17 percent were MMA fighters. The study also found that fighters with more than 25 fights were likelier to test positive for TES.

It was stressed in the study that, “It is important to emphasize that it is currently unknown what percentage of individuals who fulfill the criteria for TES actually harbor CTE pathology.” However, those who put the study together are hopeful that their approach will help research the long-term effects of RHI.

Chronic traumatic encephalopathy (CTE) can only be detected via a post-mortem exam.