In conclusion, APOE4 significantly affects cognitive decline (MCI or dementia) in the Japanese population, and the effects are significantly different between subgroups stratified by genotype for each of the three SNVs (rs1279683, rs710218, and rs841851), which were eQTLs for the brain-expressed VC transporters (SLC23A2 or SLC2A1). This evidence concerns the gene SLC23A2 and dementia.