This represents an important extension of our previous MVP study that examined gene-by-environment interaction (GxE) effects of PTSD, TBI, and APOE ε4 on ADRD risk in Veterans 65 and older using a cross-sectional (case–control) framework: that study found that the association between PTSD and TBI with ADRD was stronger as a function of APOE ε4 [42]. The gene discussed is APOE; the disease is post-traumatic stress disorder.