The main findings of this study are: (1) at 5 years post injury, patients with TBI had progressive rates of brain atrophy as reflected by decreases in GM, WM, and ventricular volume expansion compared to the baseline scan; (2) TAI is associated with the progression of brain atrophy; (3) in general, patients with TBI showed improvements in cognition and QoL over the same period; and (4) initial and longitudinal changes in serum NfL and GFAP measures independently predicted future brain volume changes. This evidence concerns the gene GFAP and Brain atrophy.