APOE ε4 allele dosage has also been shown to be a risk factor for the development of DLB, and whilst first identified over 20 years ago [14], has since been replicated in a number of studies [3, 16••, 27–30, 66].The protective effect of the ε2 allele is less well established in DLB, conferring protection in some studies [67] but not others [3]. This evidence concerns the gene APOE and Lewy body dementia.