Subconcussion Exposure in Contact and Collision Sports and the Effects on Functional Connectivity.

As concerns about long term effects of concussions in contact and collision sports have grown, similar concerns have started to extend to the repetitive subconcussive head impacts that athletes experience in sport. While the quantity and severity of subconcussive head impact has been studied in football for over a decade, little research has been done to quantify these head impacts in other contact and collision sports. Even less is known about the effects that subconcussive head impacts have on the brains of athletes. This dissertation contains a review of the biomechanical and neuroimaging literature related to head impact in sports. We present a quantification of the relative burden of head impact in college football, men’s soccer, and men’s lacrosse players. Using wearable accelerometers, it was determined that college football received the highest quantity of moderate and severe head impacts, and had the highest average impact severity. We also address whether the burden of head impacts in college football may have spatially heterogeneous effects on functional connectivity in the brains of college football players. Subconcussive head impacts may not be entirely benign, but their effects on brain connectivity are still controversial. Using mass-univariate and multivariate analyses, the results indicate that the subconcussive head impact load in college football seems to be sufficient to affect local functional connectivity and low-frequency fluctuations in the brain, and that these effects are be spatially heterogeneous. In total, this dissertation presents novel comparison of subconcussive head impact in different college men’s sports, and indicates that the subconcussive burden in college football may be sufficient to produce spatially heterogeneous changes in the brain.