The study evaluated the clinical implications of mandible and neck measurements in non-obese Asian snorers within a large group that is considered to be representative of the general population. The findings indicate that bony and soft tissue abnormalities of the mandible and neck, including thick NC in both genders and small size of mandible in males, may be relevant contributing factors for snoring.
The pathogenesis of SDB, including snoring and OSA, has been linked to anatomical, neuromuscular, ventilatory and combined factors (11
). Among these, anatomical factors that contribute to SDB are relatively easy to find from a routine physical examination, while neuromuscular or ventilatory factors can be harder to discern when subjects are awake. For this reason, studies have used craniofacial, or head and neck measurements, related to structural narrowing of the upper airway (16
). Similarly, this study was designed to determine whether manually-measured, anthropometric data for the mandible and neck could be usefully linked with snoring frequently connected with OSA in non-obese Asians.
NC is an important measurement that is reflective of soft tissue deposition within the upper airway region. NC correlates with the severity of SDB, and greater NC is related to increasing of the upper airway soft-tissue such as tongue and soft palate (18
). These outcomes closely echo the results of our present study, which revealed that both non-obese Asian male and female snorers have a significantly thicker NC, as compared to non-snorers.
Presently, non-obese Asian snorers had a significantly shorter MB than non-snorers males. These results are consistent with the findings of previous studies, which reported that mandible size is a very important risk factor related with SDB (19
). One of these earlier studies reported highly significant correlations between magnetic resonance imaging measurements and direct measurements made with a caliper and planimeter in the isolated human mandible area (19
). In addition, the authors reported that the occurrence of OSA was related to the size of the region enclosed by the mandible, as well as to a subject's weight. Moreover, a meta-analysis of the literature, evaluating the craniofacial bony contributing factors, revealed a clinically significant association between MB and diagnostic accuracy for OSA (20
). The presently-revealed shorter MB in the non-obese male snorers may be reflective of a relatively narrower oropharyngeal passage, which may result in a greater degree of crowding of the oropharyngeal soft tissue. In the non-obese females, this difference in MB was not observed to a significant degree between snorers and non-snorers. This may be attributed to differences in the bony structure and the dynamic collapsibility of the upper airway between males and females. It may also be influenced by anthropometric or hormonal differences existing between males and females.
The strength of this study is in the large number of subjects enrolled from a community-based general population, in which the repeated measurement of each parameter minimized measurement error. There are a few limitations in this study. Inter-rater or intra-rater measurement reproducibility was not assessed. However, this possibility of measurement error is likely low, since the measurement was conducted by a rater who was trained with a standardized protocol and was recorded to the nearest 1 mm. Data on the frequency of snoring was obtained from self-reports and was confirmed by the bed partner or family member. Furthermore, to compensate for this limitation, the reproducibility of the question responses on snoring was examined; the results showed that their reproducibility was high.
Among the several manually-measured anthropometric variables for the mandible and neck of non-obese Asian subjects, the NC of snorers in both non-obese males and females was greater than that of non-snorers, and that MB in non-obese male snorers was significantly reduced. The results suggest that anthropometric abnormalities of the mandible and neck, including thick neck circumference in both genders and a small jaw in males, may be relevant contributing factors for snoring in non-obese Asian snorers.