Football athletes (n = 36) show decreasing CA1 volumes with time compared to volleyball athletes (n = 23) with a significant sport by time interaction, in the absence of in-study concussion. (A) Model estimates of CA1 volume by sport over time when controlling for total intracranial volume and age, depicting a divergence of CA1 volume over time depending on sport. The shaded regions represent the 95% confidence interval (CI). (B) Model estimates of CA1 volume change over time (i.e., slope) when controlling for total intracranial volume and age, demonstrating the CA1 volume loss per year in football athletes compared to both volleyball athletes and zero, with the 95% confidence interval shown. CA1, cornu ammonis area 1. Color image is available online.