The association between MR–PRS and dementia-causing diseases was driven by SNPs in the APOE region that are associated with several BBB- and autoimmunity-related proteins such as IFIT2 (ref. 69), LRRN1 (ref. 70), TJP1 (ref. 39), KIR2DL5A71, AIMP1 (ref. 72) and BAFF receptor57, suggesting that the autoimmune component in APOE ε4 allele carriers could be related to these proteins. Here, APOE is linked to dementia.