Variants of APOE4 is associated with an increased risk of early onset AD (specifically homozygous risk allele e4), as well as genetic risk factor for late onset AD (presence of one or two copies of the e4 allele) (Cacace et al., 2016) and related dementias and sleep disturbances (Lim et al., 2013). The gene discussed is APOE; the disease is Alzheimer disease.