APOE and Parkinson disease: It is also possible that APOE4’s effect in enhancing alpha-synuclein pathology is associated with the brain changes examined, considering it a major protein pathology in PD and DLB, as well as its role in neurodegeneration independent of AD-like changes (Davis et al., 2020; Zhao et al., 2021; Calabresi et al., 2023).