Repetitive head injuries, time played linked to CTE severity in football-playing males

Key takeaways:

• Researchers examined medical, athletic histories of 631 individuals as part of two major brain studies.
• Results showed the greater time played and more hits absorbed correlated to greater CTE severity.

In football-playing males, the number and force of repetitive head injuries as well as time playing the sport were linked to severity of chronic traumatic encephalopathy, according to research published in Nature Communications.

“Chronic traumatic encephalopathy is a neurodegenerative tauopathy associated with repetitive head impacts, but the components of [repetitive head injury (RHI)] exposure underlying this relationship are unclear,” Daniel H. Daneshvar, MD, PhD, a neuroscientist in the department of physical medicine and rehabilitation, Massachusetts General Hospital, and colleagues wrote.

Researchers sought to examine the association between repeated head injuries and concussions sustained by young male football players and pathology associated with chronic traumatic encephalopathy (CTE).

They examined 631 individuals who had played football and were part of the Understanding Neurologic Injury and Traumatic Encephalopathy and Framingham Heart Study brain banks. Participants provided a history of their involvement in the game, including levels played, years played at each, age of first exposure, with a complete athletic history verified by an online database search. Neuropathologists who were blind to each participant’s history then examined each brain and diagnoses made consistent with previously established medical criteria.

Researchers then created a position exposure matrix (PEM), composed of American football helmet sensor data, summarized from a literature review which identified 34 articles by player position and level of play. Using this PEM, they estimated measures of lifetime RHI exposure for the donors. Separate models examined relationships between CTE pathology and players’ concussion count, athletic positions, years played and PEM-derived measures, including estimated cumulative head impacts, linear accelerations and rotational accelerations.

According to results, athletes died, on average, at 59.7 years old (standard deviation [SD]=20.1) and played 12.5 years of football (SD=5.9). A total of 180 athletes did not have CTE, 163 had low-stage CTE (stage I or II), and 288 had high-stage CTE (stage III or IV).

Researchers found a direct association between the mean duration of play and CTE severity, as mean duration for those without CTE was 9.5 (SD=5.3) years, for low-stage CTE 11.6 (SD=5) years and for high-stage CTE 15 (SD=5.7) years. In addition, data showed a direct relationship between the number of hits absorbed and total g-forces of those hits and CTE, with the greater amount of hits and greater g-forces correlating to higher stages of disease.

“These results provide additional evidence that repeated nonconcussive injuries are associated with CTE pathology,” Daneshvar and colleagues wrote. “This is in contrast to the emphasis on concussions that is often discussed in the medical and lay literature.”