Following bisulfite treatment, the DNA methylation status of case and control subjects was assayed using the recently developed Infinium MethylationEPIC BeadChip microarray from Illumina, Inc. (San Diego, CA, USA) according to the manufacturer's instructions, which measured the methylation status of 853,307 CpG sites distributed over the whole genome. The image intensities were extracted using the Illumina iScan system (Illumina, Inc.) and quality-controlled using RnBeads (version 3.5) (18 (link)) in R (www.r-project.org/).