Long-term impacts of concussion in American football players could be affected by position and career length

Written by Francis Davies

In the first comparative study to examine cognitively healthy footballers at both college- and career-level, researchers investigated the long-term impacts of concussion on players. While most previous research into football-based head impacts has focused on cognitively impaired footballers; the study at University of North Carolina at Chapel Hill (NC, USA), published in the journal Radiology, compared the neuroimaging of former players with no evidence of cognitive impairment, to analyze the effects that differing playing histories and exposure to concussion could have later in life.
The team recruited 64 former college and professional American football players between the ages of 52 and 64. Half had only played college football, while half had pursued their careers into the professional league. Players recruited were split equally between speed and non-speed playing positions with linemen, both offensive and defensive, making up the non-speed positions. Half of the former players reported three or more prior concussions, while the other half reported either a single concussion or no prior concussions.

To investigate the relationship between white matter structure and how brain function is affected by concussion, researchers employed both diffusion tensor imaging (DTI) and functional MRI (fMRI) scans; despite their individual use in previous research it was one of the first studies to utilize both methods. DTI scans were used to determine structural integrity, while fMRI was used to asses function while players performed a memory task.

Non-speed players with a history of recurrent concussion displayed reduced frontal white matter integrity alongside a lower level of activation during the fMRI task, in comparison with players with no history or only a single concussion. The speed players did not reflect this.

The interactions observed between position played and concussion histories suggest that there may be essential differences between speed and non-speed players, with the magnitude, location and frequency of head impacts differing dependent on position. Offensive backs were discovered to experience impacts at greater acceleration, while linemen tend to experience a greater overall number of impacts, including those to the front of the helmet. As the mechanisms of concussions on non-speed players are fundamentally different to those of speed players, this may imply that position specific helmets are necessary.

Researchers speculate that the number of players with an extended career in football and a history of recurrent concussions, but who remain cognitively normal into their late 50s, may in fact be outliers; unreflective of the football playing population overall.

Michael Clark (University of North Carolina) elaborated: “We’re not exactly sure why this is the case for the former pros. It may have to do with the sample of athletes we recruited into the study. But the findings could suggest that a career with additional exposure to football is not necessarily worse than a shorter duration of exposure.”

Researchers specified that further research was necessary to determine the underlying mechanisms of both subconcussive and concussive impacts on brain health over extended periods of time into later life.

Sources: Clark MD, Varangis EML, Champagne AA et al. Effects of Career Duration, Concussion History, and Playing Position on White Matter Microstructure and Functional Neural Recruitment in Former College and Professional Football Athletes. doi:10.1148/radiol.2017170539 (2017) (Epub ahead of print); www.eurekalert.org/pub_releases/2017-10/rson-fpa102417.php