Although our observations corroborate prior accounts linking APOE loci to WMHV in the UK Biobank,15, 16, 17 all of which suggest that AD risk at the APOE locus increases WMHV, this is the first evidence to our knowledge linking AD genetic risk in SMCs to WHMV and to any AD imaging biomarkers, more broadly. Here, APOE is linked to Alzheimer disease.