APOE and Alzheimer disease: Given that certain SNPs in apolipoprotein genes have been linked to an increased risk of AD, we also set out to interrogate whether those at increased genetic risk of AD also have altered Aβ dynamics in response to sleep loss, a largely unexplored area of inquiry.18 In this context, the G and G/G variant of the SNP rs4420638 (within the apolipoprotein gene APOC1) have been associated with an increased risk of AD,17,19 by being in linkage disequilibrium with the canonical AD risk gene APOE,17 and thus affecting metabolism of Aβ species.