Using whole genome DNA methylation analysis, we have identified interleukin 1 receptor type 2 hypomethylation and androgen receptor hypermethylation as an important determinant of disease severity of OSA, and natriuretic peptide 2 hypomethylation and speckled protein 140 hypermethylation as a biomarker for vulnerability to excessive daytime sleepiness (EDS) in OSA [16]. This evidence concerns the gene IL1R2 and obstructive sleep apnea syndrome.