Cephalometric abnormalities in non-obese and obese patients with obstructive sleep apnoea.
Level 4 - case-series / case-control
Cross-sectional comparative case-control study
PubMed 10065689 · doi:10.1183/09031936.99.13240399
What was done
Researchers evaluated 48 lateral cephalometric variables in 114 Japanese men with obstructive sleep apnea (OSA) and 37 healthy male controls. The OSA cohort was stratified into non-obese (BMI < 27 kg/m², n = 54, mean AHI 25.3 ± 16.1 events/h) and obese (BMI ≥ 27 kg/m², n = 60, mean AHI 45.6 ± 28.0 events/h) groups. All OSA patients and 19 of the 37 controls underwent diagnostic polysomnography. Cephalometric abnormalities were compared against BMI-matched controls, and stepwise regression models were run within each OSA subgroup to identify structural determinants of AHI.
What was found
Non-obese OSA patients exhibited reduced anteroposterior facial dimensions (cranial base, maxilla, mandible), narrower bony pharynx width, enlarged tongue with inferior volume displacement, enlarged soft palate, inferiorly positioned hyoid, and reduced airway width across four levels compared to controls. Obese OSA patients showed more extensive soft tissue enlargement with fewer bony anomalies. In non-obese patients, AHI severity was significantly determined by two bony variables: anterior cranial base length (S-N) and mandibular length (Me-Go). In obese patients, AHI was predicted by the distance between the anterior vertebra and hyoid bone (H-VL), which correlated with soft tissue measurements including total tongue area, inferior tongue area, and pharyngeal airway length.
Why it matters
The study demonstrates that the anatomical drivers of OSA differ by body habitus: craniofacial skeletal constraints are the primary determinants in non-obese individuals, whereas soft tissue enlargement dominates in obese individuals.
Limits
The cohort was exclusively male and Japanese, limiting generalizability to females and other ethnic groups. Only 19 of the 37 healthy controls received confirmatory polysomnography to rule out subclinical sleep-disordered breathing. The cross-sectional design demonstrates anatomical associations with AHI but cannot establish causal sequence.
Cited by
- supports Sleep apnea can occur in individuals with a normal BMI, including a BMI of 21.