Heritability of the airway structure and head posture using twin study.

Inherited traits of obstructive sleep apnoea (OSA) may have link to the heritability of the airway anatomy. The aim of this study was to investigate heritability of the airway anatomy by comparing skeletal and soft tissue features of Korean monozygotic twins (MZ) and dizygotic twins (DZ). In total, 72 participants (mean age, 41.5 ± 5.9 years; 40 males, 32 females) including 48 MZ (24 pairs) and 24 DZ (12 pairs) with same sex were participated. The craniofacial, craniovertebral, hyoideal and pharyngeal parameters were measured using lateral cephalograms. The genetic analysis was performed using Falconer's method. High heritability was detected in the hyoid position and inclination of the cervical column. The velopharyngeal and hypopharyngeal dimensions showed higher heritability compared to those of the nasopharynx and oropharynx. The body mass index (BMI) had interactions with the nasopharyngeal and hypopharyngeal dimensions and length of the tongue and soft palate. The mandibular growth had correlations with the nasopharyngeal and hypopharyngeal dimensions. The vertical skeletal relationships appeared to have interaction with the nasopharyngeal, velopharyngeal and hypopharyngeal dimensions, as well as length of the tongue and soft palate. A forwarded inclination of the cervical columns was seen in connections with BMI and the nasopharyngeal and hypopharyngeal dimensions. The airway structures and head postures seemed to be under strong genetic controls. The airway dimensions had associations with BMI, head postures and skeletal structures which showed high heritability. Forwarded head postures would be physiological adaptations of compromised airway adequacy by increased BMI and retrognathia.