title: Clinical characteristics of obesity-hypoventilation syndrome in Japan: a multi-center study.
abstract: OBJECTIVE
  To clarify the prevalence and clinical characteristics of obesity-hypoventilation syndrome (OHS) in a large number of patients with moderate to severe obstructive sleep apnea syndrome (OSAS).
  
  
  METHODS
  Subjects comprised 611 patients with OSAS registered from 7 sleep centers and clinics and analyzed according to the definitions of the Respiratory Failure Research Group of the Japanese Ministry of Health and Welfare. Baseline characteristics, polysomnographic data during sleep, laboratory blood examinations, excessive daytime sleepiness, pulmonary functions, and arterial blood gases were compared between OHS and non-OHS patients. Determinants of daytime hypercapnia were also examined in OHS patients.
  
  
  RESULTS
  OHS was identified in 55 of the 611 patients with OSAS (9%). OHS patients were younger, heavier, and more somnolent than non-OHS patients and displayed more severe OSAS, liver dysfunctions, higher total cholesterol, and impaired pulmonary function. However, these differences were resolved except for pulmonary function after correction for obesity. Daytime hypercapnia was associated with impaired pulmonary function. Percent vital capacity (%VC) was most closely correlated with PaCO2 in OHS.
  
  
  CONCLUSIONS
  OHS patients display numerous abnormalities due to obesity compared with non-OHS patients. Impaired pulmonary function, particularly %VC, may play an important role in the development of daytime hypercapnia independent of obesity in OHS patients.
authors.affiliation: Respiratory Medicine, Nihon University School of Medicine, Tokyo.
authors.forename: Tsuneto
authors.initials: T
authors.lastname: Akashiba
authors.forename: Toshiki
authors.initials: T
authors.lastname: Akahoshi
authors.forename: Seiji
authors.initials: S
authors.lastname: Kawahara
authors.forename: Akihito
authors.initials: A
authors.lastname: Uematsu
authors.forename: Kazuhito
authors.initials: K
authors.lastname: Katsura
authors.forename: Shigeru
authors.initials: S
authors.lastname: Sakurai
authors.forename: Akira
authors.initials: A
authors.lastname: Murata
authors.forename: Hiroki
authors.initials: H
authors.lastname: Sakakibara
authors.forename: Kazuo
authors.initials: K
authors.lastname: Chin
authors.forename: Wataru
authors.initials: W
authors.lastname: Hida
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nakamura
mesh_terms: D000328:Adult; D000410:Alanine Transaminase / Q000097:blood; D000469:Alkaline Phosphatase / Q000097:blood; D001219:Aspartate Aminotransferases / Q000097:blood; D015992:Body Mass Index; D002245:Carbon Dioxide / Q000097:blood; D015897:Comorbidity; D005260:Female; D006400:Hematocrit; D006801:Humans; D006935:Hypercapnia / Q000097:blood / Q000453:epidemiology* / Q000209:etiology; D006937:Hypercholesterolemia / Q000453:epidemiology; D007564:Japan / Q000453:epidemiology; D008107:Liver Diseases / Q000097:blood / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications / Q000453:epidemiology*; D010845:Obesity Hypoventilation Syndrome / Q000150:complications / Q000453:epidemiology* / Q000473:pathology; D010100:Oxygen / Q000097:blood; D010313:Partial Pressure; D017286:Polysomnography; D015995:Prevalence; D020181:Sleep Apnea, Obstructive / Q000453:epidemiology; D013147:Spirometry; D014797:Vital Capacity
chemical_list: D002245:Carbon Dioxide; D001219:Aspartate Aminotransferases; D000410:Alanine Transaminase; D000469:Alkaline Phosphatase; D010100:Oxygen