Analysis of anatomical and functional determinants of obstructive sleep apnea.

PURPOSE: Craniofacial abnormalities have an important role in the occurrence of obstructive sleep apnea (OSA) and may be particularly significant in Asian patients, although obesity and functional abnormalities such as reduced lung volume and increased airway resistance also may be important. We conducted simultaneous analyses of their interrelationships to evaluate the relative contributions of obesity, craniofacial structure, pulmonary function, and airway resistance to the severity of Japanese OSA because there are little data in this area.

METHODS: A cross-sectional observational study was performed on 134 consecutive Japanese male patients. A sleep study, lateral cephalometry, pulmonary function tests, and impulse oscillometry (IOS) were performed on all patients.

RESULTS: Age, body mass index (BMI), position of the hyoid bone, and proximal airway resistance on IOS (R20) were significantly related to the apnea/hypopnea index (AHI) (p < 0.05) in multiple regression analysis. Subgroup analysis showed that, for moderate-to-severe OSA (AHI ≥ 15 events/h), neck circumference and R20 were predominantly related to AHI, whereas for non-to-mild OSA (AHI < 15 events/h), age and expiratory reserve volume were the predominant determinants. In obese subjects (BMI ≥ 25 kg/m(2)), alveolar-arterial oxygen tension difference, position of the hyoid bone, and R20 were significantly associated with AHI, whereas age alone was a significant factor in nonobese subjects (BMI < 25 kg/m(2)).

CONCLUSIONS: Aside from age and obesity, anatomical and functional abnormalities are significantly related to the severity of Japanese OSA. Predominant determinants of AHI differed depending on the severity of OSA or the magnitude of obesity.