For this reason, it is perhaps not surprising that the handful of studies that have compared the levels of Aß in APOE4+ vs. APOE4− AD patients have shown conflicting results, with some studies reporting increased Aß levels in the brains of APOE4+ AD patients compared to APOE4− AD patients [81, 93, 94], some reporting no changes in Aß levels between these two groups [95, 96], and some reporting decreased Aß levels in the brains of APOE4+ AD patients compared to APOE4− AD patients [97, 98] (Table 4). Here, APOE is linked to Alzheimer disease.