Editors' Note: Association of Position Played and Career Duration and Chronic Traumatic Encephalopathy at Autopsy in Elite Football and Hockey Players.

In their retrospective autopsy series of 35 former football and hockey players, Schwab and colleagues found that half (49%) had histopathologic evidence of chronic traumatic encephalopathy (CTE) based on 2015 NINDS consensus criteria. Among their findings, the investigators reported no significant association between CTE risk and surrogate markers for lifetime exposure to sport and aggressive role/style of play, although the study was limited by its small sample size. The investigators conclude that factors other than cumulative physical contact and injury insufficiently explain the risk of CTE. Dr. Mez and colleagues compared these results from their recently published autopsy series of 266 former football players, in which the odds of CTE increased by 30% for every year of football played. In their work, Mez et al. also report no effect of player position (similar to the results of Schwab et al.); however, Mez et al. indicate that the findings reported here were too underpowered to detect any significant relationship between CTE and position or exposure duration. Furthermore, comments by Mez as well as Dr. Dams-O’Connor highlight important limitations in selection of the independent variables, particularly that the surrogate marker for duration of exposure (age at retirement) inadequately captures preprofessional duration of play. Preprofessional exposure and head injury have been shown in some studies to pose considerable risk as injuries accumulate in the developing brains of children and adolescents. The investigators acknowledge the limitation in statistical power, but reiterate a major conclusion that even subjects with relatively brief exposure to contact sports remain at risk of this histopathologic diagnosis, whereas others with protracted exposure may not develop this brain pathology. In their retrospective autopsy series of 35 former football and hockey players, Schwab and colleagues found that half (49%) had histopathologic evidence of chronic traumatic encephalopathy (CTE) based on 2015 NINDS consensus criteria. Among their findings, the investigators reported no significant association between CTE risk and surrogate markers for lifetime exposure to sport and aggressive role/style of play, although the study was limited by its small sample size. The investigators conclude that factors other than cumulative physical contact and injury insufficiently explain the risk of CTE. Dr. Mez and colleagues compared these results from their recently published autopsy series of 266 former football players, in which the odds of CTE increased by 30% for every year of football played. In their work, Mez et al. also report no effect of player position (similar to the results of Schwab et al.); however, Mez et al. indicate that the findings reported here were too underpowered to detect any significant relationship between CTE and position or exposure duration. Furthermore, comments by Mez as well as Dr. Dams-O’Connor highlight important limitations in selection of the independent variables, particularly that the surrogate marker for duration of exposure (age at retirement) inadequately captures preprofessional duration of play. Preprofessional exposure and head injury have been shown in some studies to pose considerable risk as injuries accumulate in the developing brains of children and adolescents. The investigators acknowledge the limitation in statistical power, but reiterate a major conclusion that even subjects with relatively brief exposure to contact sports remain at risk of this histopathologic diagnosis, whereas others with protracted exposure may not develop this brain pathology.