[1] Mahidol Univ, Dept Med, Pulm & Crit Care Unit, Sleep Disorder Ctr,Ramathibodi Hosp, Bangkok 10700, Thailand
[2] Stanford Univ, Sleep Med Div, Stanford, CA 94305 USA
[3] Catholic Univ Korea, St Vincents Hosp, Coll Med, Dept Otolaryngol Head & Neck Surg, Suwon, South Korea