Clinical characteristics of obesity-hypoventilation syndrome in Japan: a multi-center study.
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.
Akashiba
Tsuneto
T
Respiratory Medicine, Nihon University School of Medicine, Tokyo.
Akahoshi
Toshiki
T
Kawahara
Seiji
S
Uematsu
Akihito
A
Katsura
Kazuhito
K
Sakurai
Shigeru
S
Murata
Akira
A
Sakakibara
Hiroki
H
Chin
Kazuo
K
Hida
Wataru
W
Nakamura
Hiroshi
H
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
D002245:Carbon Dioxide; D001219:Aspartate Aminotransferases; D000410:Alanine Transaminase; D000469:Alkaline Phosphatase; D010100:Oxygen