CYP46A1 and Alzheimer disease: Janson et al. (2004) suggested a strong link between the neurodegenerative processes that lead to the loss of cortical brain cells in AD and the loss of β-cells in T2DM. Many previous studies, including our study, have explored the relationship between CYP46A1 gene polymorphisms and AD or MCI and reached some inconsistent conclusions. Some studies focused on the relationship between the CYP46A1 gene polymorphism and T2DM. In Rizvi et al.’s (2017) study, CC, CT genotypes, and C allele were found to be positive risk factors for T2DM.