By contrast, CpG1 (P = 0.003) and CpG3 (P = 5.87 × 10<sup>-7</sup>) were highly methylated among the EH subjects compared with the controls, whereas CpG2 (P = 1.24 × 10<sup>-12</sup>) was significantly less methylated in among EH subjects.
Receiver operating characteristic curve analysis showed that CpG2 (area under curve: 0.638, P=0.001) and CpG3 (area under curve: 0.704, P<0.001) had a diagnostic value to predict the risk of EH.
The potential effects of the interactions between DNA methylation (CpG1 and CpG2-5 methylation levels) of the α-adducin (ADD1) gene promoter and ADD1 tagSNPs (tag single-nucleotide polymorphisms) or the environmental factors on essential hypertension (EH) risk have not been clarified.
CpG2-5 methylation was shown as a significant predictor of EH in males [area under curve (AUC) = 0.855, P = 0.001], in contrast that CpG1 methylation was a trend toward indicator in females (AUC = 0.699, P = 0.054).