Facial axis angle as a risk factor for obstructive sleep apnea.

Objective: Many Japanese patients with obstructive sleep apnea (OSA) are less obese than Caucasian OSA patients despite their similar severity of OSA, suggesting that their etiology of OSA may differ. The purpose of this study was to identify bony factors associated with OSA in the Japanese population.

Methods: The clinical records of study subjects were retrospectively reviewed, and cephalometric measurements based on Sella-Nasion references and the Ricketts method were statistically compared.

Patients: Two hundred and six consecutive Japanese men complaining of habitual snoring and daytime sleepiness were enrolled in the study. All subsequently underwent an overnight polysomnographic examination.

Results: Multiple regression analysis showed that the body mass index (p<0.0001) and facial axis angle (p=0.007) were the dominant overall determinants for the apnea hypopnea index. The sella to nasion to subspinale angle (SNA) and sella to nasion to supramentale angle (SNB) were lower in the non-obese, severe group than for non-obese, mild and moderate patients with OSA (p=0.0047 and 0.0016, respectively).

Conclusion: The risk factors for OSA in Japanese men may be obesity and the dolico facial pattern seen by the Ricketts method. In addition, a smaller SNA and SNB seem to be associated with the severity of OSA in non-obese patients.