APOE and Parkinson disease: For the 7 specific ROIs, only the left angular gyrus (AnG) showed a significant difference in GMV between the two study groups for both unadjusted analyses (t83.42 = −2.568, p = 0.012) and in ANCOVA models adjusted for age, sex, disease duration, and TIV (F1,165 = 6.702, p = 0.010) (Fig 1, S1 Table), with PD APOE4 carriers exhibiting higher GMV than non-carriers.