To assess differences in FOXP3 methylation levels in OSA versus non-OSA subjects, we selected the first 16 patients with severe OSA (Apnea-Hypopnea Index—AHI > 30) and seven healthy subjects (AHI < 5) matched by age (± 2 years) and body mass index (BMI) (± 2 kg/m2). The gene discussed is FOXP3; the disease is obstructive sleep apnea syndrome.