Longitudinal alteration of cortical thickness and volume in high-impact sports

Collegiate football athletes are subject to repeated head impacts. The purpose of this study was to determine whether this exposure can lead to changes in brain structure. This prospective cohort study was conducted with up to 4 years of follow-up on 63 football (high-impact) and 34 volleyball (control) male collegiate athletes with a total of 315 MRI scans (after exclusions: football n ​= ​50, volleyball n ​= ​24, total scans ​= ​273) using high-resolution structural imaging. Volumetric and cortical thickness estimates were derived using FreeSurfer 5.3's longitudinal pipeline. A linear mixed-effects model assessed the effect of group (football vs. volleyball), time from baseline MRI, and the interaction between group and time. We confirmed an expected developmental decrement in cortical thickness and volume in our cohort (p ​< ​.001). Superimposed on this, total cortical gray matter volume (p ​= ​.03) and cortical thickness within the left hemisphere (p ​= ​.04) showed a group by time interaction, indicating less age-related volume reduction and thinning in football compared to volleyball athletes. At the regional level, sport by time interactions on thickness and volume were identified in the left orbitofrontal (p ​= ​.001), superior temporal (p ​= ​.001), and postcentral regions (p ​< ​.001). Additional cortical thickness interactions were found in the left temporal pole (p ​= ​.003) and cuneus (p ​= ​.005). At the regional level, we also found main effects of sport in football athletes characterized by reduced volume in the right hippocampus (p ​= ​.003), right superior parietal cortical gray (p ​< ​.001) and white matter (p ​< ​.001), and increased volume of the left pallidum (p ​= ​.002). Within football, cortical thickness was higher with greater years of prior play (left hemisphere p ​= ​.013, right hemisphere p ​= ​.005), and any history of concussion was associated with less cortical thinning (left hemisphere p ​= ​.010, right hemisphere p ​= ​.011). Additionally, both position-associated concussion risk (p ​= ​.002) and SCAT scores (p ​= ​.023) were associated with less of the expected volume decrement of deep gray structures. This prospective longitudinal study comparing football and volleyball athletes shows divergent age-related trajectories of cortical thinning, possibly reflecting an impact-related alteration of normal cortical development. This warrants future research into the underlying mechanisms of impacts to the head on cortical maturation.