Traumatic Encephalopathy Syndrome: Head Impact Exposure and Blood Biomarkers in Professional Combat Athletes.

Objective: This study aimed to (1) determine whether there was an association between a diagnosis of traumatic encephalopathy syndrome (TES) and changes in three specific serum biomarkers, and (2) determine head impact exposure thresholds among both TES+ and TES- groups.

Setting: Data were collected from Cleveland Clinic's Professional Athletes Brain Health Study (PABHS).

Participants: This study included 192 professional combat athletes, 35 years of age and older. Athletes must be actively fighting or retired with a minimum of 10 professional fights over their careers.

Design/intervention: This was a retrospective observational study of the PABHS longitudinal cohort.

Main measures: The generalized linear model with the generalized estimating equation for repeated measurements was used to compare various biomarkers between both active and retired TES- and TES+ groups.

Results: The odds ratio for TES diagnosis was 5.44 (95% CI = 2.48, 11.94; P < .0001) among active fighters and 10.75 (95% CI = 3.52, 32.85; P < .0001) among retired fighters, indicating the odds for a TES diagnosis were over 5 times greater for active fighters with every fight completed at or beyond 30 professional fights. Retired fighters had 10 times greater odds of TES diagnosis with every fight completed at or beyond 15 professional fights. Likewise, the odds of a TES diagnosis were 2.0% (95% CI = 0.3, 3.1; P = 0.0039) greater with each pg/mL increase of glial fibrillary acidic protein (GFAP). No relationship was observed between a TES diagnosis and neurofilament light chain or P-tau231.

Conclusion: This study provides preliminary evidence that progressively elevated levels of the GFAP blood biomarker increase the odds of a TES diagnosis among retired professional fighters. Further evaluation is required to improve clarity and understanding of the relationship between progressive changes in the GFAP blood biomarker and a TES diagnosis, specifically evaluating the duration of chronicity and exposure thresholds.