SLEEP DISORDERED BREATHING

Craniofacial profile in Asian and white subjects with obstructive sleep apnoea

B Lam¹, M S M Ip¹, E Tench² and C F Ryan²

¹ University of Hong Kong, Hong Kong SAR, China
² Department of Medicine, University of British Columbia, Vancouver, BC, Canada

Correspondence to:
Correspondence to:
Dr C F Ryan
UBC Respiratory Clinic, Vancouver General Hospital, 2775 Heather Street, Vancouver, BC, V5Z 3J5, Canada; fryan{at}interchange.ubc.ca

Background: Clinical detection of structural narrowing of the upper airway may facilitate early recognition of obstructive sleep apnoea (OSA). To determine whether the craniofacial profile predicts the presence of OSA, the upper airway and craniofacial structure of 239 consecutive patients (164 Asian and 75 white subjects) referred to two sleep centres (Hong Kong and Vancouver) were prospectively examined for suspected sleep disordered breathing.

Methods: All subjects underwent a history and physical examination with measurements of anthropometric parameters and craniofacial structure including neck circumference, thyromental distance, thyromental angle, and Mallampati oropharyngeal score. OSA was defined as an apnoea-hypopnoea index (AHI) of 5/hour on full overnight polysomnography.

Results: Discriminant function analysis indicated that the Mallampati score (F = 0.70), thyromental angle (F = 0.60), neck circumference (F = 0.54), body mass index (F = 0.53), and age (F = 0.53) were the best predictors of OSA. After controlling for ethnicity, body mass index and neck circumference, patients with OSA were older, had larger thyromental angles, and higher Mallampati scores than non-apnoeic subjects. These variables remained significantly different between OSA patients and controls across a range of cut-off values of AHI from 5 to 30/hour.

Conclusions: A crowded posterior oropharynx and a steep thyromental plane predict OSA across two different ethnic groups and varying degrees of obesity.

Abbreviations: AHI, apnoea-hypopnoea index; BMI, body mass index; MS, Mallampati score; NC, neck circumference; OSA, obstructive sleep apnoea; OSAHS, obstructive sleep apnoea-hypoponea syndrome; TMA, thyromental angle; TMD, thyromental distance

Keywords: sleep apnoea; craniofacial structure; upper airway; ethnicity; prediction equations

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