PRKN and Alzheimer disease: Of these common DMPs, 6 CpG sites were continuously and significantly hypermethylated (i.e., DNA methylation level: AD > MCI > CHCs) in MCI and AD samples compared to CHCs (Padj < 0.05), including RHOJ cg18771300, RHOJ cg07157030, RHOJ cg07189587, PARK2 cg09656629, cg22100363, and FLNC cg20186636 (Figures 5A–F), while 5 CpG sites were continuously and significantly hypomethylated (i.e., DNA methylation level CHCs > MCI > AD) in MCI and AD groups relative to CHCs (Padj < 0.05), such as cg24361198, ANKH cg02821156, cg15970769, cg22721608, and AFAP1 cg06758191 (Figures 5G–K).