In the total eight samples including ED and AD groups, a significant correlation between methylation β-value and age was found in 6 genes (CARD14, CRHR1, GNL3, SNORA52, XKR5, and MED23); however, the remaining two genes (C24orf139 and ZBTB47) showed no significant correlation between methylation β value and age (Fig 5). This evidence concerns the gene XKR5 and Alzheimer disease.