We have analyzed methylation in two different regulatory regions of the FOXP3 gene, located in the promoter and in the Treg-specific demethylated region, and contrary to what happens in children with OSA, we have not found differences in FOXP3 methylation or Treg levels between patients with OSA and healthy subjects, even when patients were grouped according with the coexistence of systemic inflammation. Here, FOXP3 is linked to obstructive sleep apnea syndrome.