APOE and Alzheimer disease: A close investigation into the scatter plots of instrumental SNPs showed that the causal effect of AD on BAG was primarily driven by a SNP (rs59007384) in the APOE region, which was not identified as a horizontal pleiotropic instrument by MR-PRESSO (outlier test p > 0.05) (Fig. 3c); there were no extreme instruments identified for the BIP to BAG relation by MR-PRESSO (Fig. 3d) but Egger-regression indicated existence of horizontal pleiotropy (Egger intercept test: p = 0.017).