A cluster analysis of keywords was performed to explore the central knowledge framework in the field of study, resulting in the division of the study into 9 clusters, as illustrated in Figure 7B: Cluster #0 focuses on Parkinson's disease, Cluster #1 on histone acetylation, Cluster #2 on meta‐analysis, Cluster #3 on amyotrophic lateral sclerosis, Cluster #4 on multiple sclerosis, Cluster #5 on Alzheimer's disease, Cluster #6 on N6‐methyladenosine, Cluster #7 on DNA methylation, and Cluster #8 on apolipoprotein E. Here, APOE is linked to Parkinson disease.