It is important to note that current EWAS studies are limited by methods they used to measure DNA methylation (bead chip vs. sequencing-based methods, comparisons discussed in [34]. Most studies used arrays due to their cheaper cost, ease of use, consistency among large number of samples, and availability of well-established analytical tools. Even if Illumines bead arrays were utilized, the content of probes included (Golden gate vs. 27K vs. 450K) limited the number of CpG sites discovered. Furthermore, most of current studies replied on bisulfate treatment, which studied the sum of 5-methylcytosine (5mC), an oxidized form of 5-methylcytosine, and its base, 5hmC (5-hydroxymethylcytosine), instead of each modification individually.