Assessment of somatosensory and cognitive-motor processing time in retired athletes with a history of repeated head trauma

Measurement of the adverse outcomes of repeated head trauma in contact sport athletes is often achieved using tests where the comparator is the score or the accuracy obtained. While it is expected that ex-athletes would perform worse than controls, previous studies have shown inconsistent results. Here we have attempted to address these inconsistencies from a different perspective by quantifying not only accuracy, but also the time of motor responses (response time). We tested age-matched control subjects who have never experienced head trauma (n=20; 41.8 {+/-} 14.4 years), and two cohorts of retired contact sport athletes with a history of head trauma and concussions; one with self-reported concerns (n=36; 45.4 {+/-} 12.6 years), and another with no ongoing concerns (n=19; 43.1 {+/-} 13.5 years). Participants performed cognitive (Cogstate) and somatosensory (Cortical Metrics) testing and both accuracy and response time were recorded. Transcranial magnetic stimulation (TMS) was undertaken to investigate corticospinal conduction and excitability. Results showed that in both test batteries there was little difference between groups when considering only accuracy scores. By contrast, response times in all but one test revealed that ex-athletes with self-reported concerns were significantly slower compared to no concern ex-athlete or control groups (p ranges 0.031 to <0.001). TMS latency showed significantly increased conduction time (p=0.008) in the group with ongoing concerns. These findings suggest that incorporating response times in cognitive and somatosensory testing is more informative than considering accuracy scores alone when assessing cognitive processing ability in retired contact sport athletes with ongoing brain health concerns.