APOE and neurodegenerative disease: Human APOE exists as three common alleles (APOE2, APOE3, and APOE4); APOE4 occurs in nearly 25% of the US population, and is the strongest genetic risk factor for dementia associated with neurodegenerative diseases such as AD and Diffuse Lewy Body Disease (Chen et al., 2021; Dickson et al., 2018; Zhao et al., 2020).