title: Clinical features in patients with positional obstructive sleep apnea according to its subtypes.
abstract: OBJECTIVE
  This study aimed to determine the prevalence of positional obstructive sleep apnea (OSA) and its subtypes in Korean adults with newly diagnosed OSA and document the clinical characteristics of positional OSA and its subtypes compared to non-positional OSA METHODS: In this cross-sectional study, we evaluated 1052 OSA adults. Positional OSA was defined as an overall apnea-hypopnea index (AHI) ≥5 and supine AHI to non-supine AHI ratio of ≥2. Positional OSA was subtyped depending on the degree of AHI while in the non-supine position: subtype I (a non-supine AHI <5/h), subtype II (a non-supine AHI ≥5/h and <15/h), and subtype III (a non-supine AHI ≥15/h). To compare clinical characteristics between patient groups depending on the positional tendency of OSA, statistical analyses were performed.
  
  
  RESULTS
  The prevalence of positional OSA was 75.6 % with 39.9 % having AHI normalized <5/h while in non-supine position. Positional OSA patients had milder OSA, older age, and lower BMI than did non-positional OSA patients. However, having positional OSA did not influence daytime sleepiness, depressive symptoms, anxiety, and health-related quality of life. Unlike the subtype I and II positional OSAs, subtype III did not differ in clinical features from non-positional OSA. There were significant differences in supine sleep time depending on the positional tendency of OSA. Subtype III positional OSA had the shortest supine sleep time whereas subtype I positional OSA and non-positional OSA had the longest supine sleep time.
  
  
  CONCLUSIONS
  Positional OSA subtypes have different clinical characteristics. Subtyping of positional OSA is helpful for developing specific treatment strategies according to positional tendency.
authors.affiliation: Department of Neurology, Asan Medical Center, University of Ulsan College of Medicine, 88, Olympic-ro 43-gil, Songpa-gu, Seoul, 138-736, Republic of Korea. salee@amc.seoul.kr.
authors.forename: Sang-Ahm
authors.identifier: http://orcid.org/0000-0002-6743-0545
authors.initials: SA
authors.lastname: Lee
authors.affiliation: Department of Neurology, Asan Medical Center, University of Ulsan College of Medicine, 88, Olympic-ro 43-gil, Songpa-gu, Seoul, 138-736, Republic of Korea.
authors.forename: Joon-Hyun
authors.initials: JH
authors.lastname: Paek
authors.affiliation: Department of Otolaryngology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea.
authors.forename: Yoo-Sam
authors.initials: YS
authors.lastname: Chung
authors.affiliation: Department of Pulmonary Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea.
authors.forename: Woo Sung
authors.initials: WS
authors.lastname: Kim
mesh_terms: D000328:Adult; D000368:Aged; D003430:Cross-Sectional Studies; D006970:Disorders of Excessive Somnolence / Q000145:classification / Q000175:diagnosis / Q000453:epidemiology; D006801:Humans; D007723:Korea; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D017286:Polysomnography; D020181:Sleep Apnea, Obstructive / Q000145:classification / Q000175:diagnosis* / Q000453:epidemiology; D016683:Supine Position; D011795:Surveys and Questionnaires
chemical_list: D010100:Oxygen
keywords: Obstructive sleep apnea; Positional; Sleep disordered breathing; Subtype; Supine sleep; Supine-isolated; Supine-predominant