Out of the total 36 DEGs in the blood studies, 19 were previously known to be associated with several other neurodegenerative diseases, such as Alzheimer’s disease and four common genes (HSPA6, MAP2K6, SRPK2 and NOL7) were also previously associated with PD (named PD-specific genes)(identified using GCBI online software). Here, NOL7 is linked to Alzheimer disease.