title: Two subtypes of positional obstructive sleep apnea: Supine-predominant and supine-isolated.
abstract: OBJECTIVE
  The body position has a strong influence on obstructive sleep apnea (OSA). The purpose of this study is to compare the clinical features of two subtypes of positional OSA (POSA), namely supine-predominant OSA (spOSA) and supine-isolated OSA (siOSA), so as to discuss whether the two groups can be classified separately.
  
  
  METHODS
  A total of 279 consecutive patients with OSA were enrolled. The POSA was defined as having an overall apnea-hypopnea index (AHI) ⩾ 5 with supine AHI > 2 times the non-supine AHI. Only those with ⩾ 30 min spent in the supine and non-supine sleeping positions were included, and split night studies were excluded from the study. Patients were considered spOSA unless their non-supine AHI was negligible (<5) (siOSA). The clinical and polysomnographic characteristics of both groups were compared.
  
  
  RESULTS
  Two hundred and sixteen subjects (77.4%) met the criteria for POSA, with 158 (73.1%) of them classified as spOSA, and 58 (26.9%) as siOSA. The siOSA patients had lower arousal indices, but poorer quality of sleep, and were more depressed and anxious compared with the spOSA subjects.
  
  
  CONCLUSIONS
  Those with siOSA and spOSA show different clinical features.
  
  
  CONCLUSIONS
  These findings suggest that a more detailed sub-classification of POSA is needed.
authors.affiliation: Department of Neurology, Dongsan Medical Center, Keimyung University School of Medicine, Daegu, South Korea.
authors.forename: Keun Tae
authors.initials: KT
authors.lastname: Kim
authors.affiliation: Department of Neurology, Dongsan Medical Center, Keimyung University School of Medicine, Daegu, South Korea. Electronic address: neurocho@gmail.com.
authors.forename: Yong Won
authors.initials: YW
authors.lastname: Cho
authors.affiliation: Department of Otorhinolaryngology, Dongsan Medical Center, Keimyung University School of Medicine, Daegu, South Korea.
authors.forename: Dong Eun
authors.initials: DE
authors.lastname: Kim
authors.affiliation: Department of Dentistry, Dongsan Medical Center, Keimyung University School of Medicine, Daegu, South Korea.
authors.forename: Sang Hee
authors.initials: SH
authors.lastname: Hwang
authors.affiliation: Department of Graduate School of Nursing, Dongsan Medical Center, Keimyung University School of Medicine, Daegu, South Korea.
authors.forename: Mei Ling
authors.initials: ML
authors.lastname: Song
authors.affiliation: Department of Neurology, Georgetown University Hospital, Washington, DC, USA.
authors.forename: Gholam K
authors.initials: GK
authors.lastname: Motamedi
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017286:Polysomnography / Q000379:methods; D011187:Posture / Q000502:physiology; D020181:Sleep Apnea, Obstructive / Q000145:classification* / Q000175:diagnosis* / Q000503:physiopathology; D016683:Supine Position / Q000502:physiology*
keywords: OSA classification; Obstructive sleep apnea; Positional obstructive sleep apnea; Supine OSA