Upper airway structure and body fat composition in obese children with obstructive sleep apnea syndrome

Abstract

Rationale: Mechanisms leading to obstructive sleep apnea syndrome (OSAS) in obese children are not well understood.

Objectives: The aim of the study was to determine anatomical risk factors associated with OSAS in obese children as compared with obese control subjects without OSAS.

Methods: Magnetic resonance imaging was used to determine the size of upper airway structure, and body fat composition. Paired analysis was used to compare between groups. Mixed effects regression models and conditional multiple logistic regression models were used to determine whether body mass index (BMI) Z-score was an effect modifier of each anatomic characteristic as it relates to OSAS.

Measurements and main results: We studied 22 obese subjects with OSAS (12.5 ± 2.8 yr; BMI Z-score, 2.4 ± 0.4) and 22 obese control subjects (12.3 ± 2.9 yr; BMI Z-score, 2.3 ± 0.3). As compared with control subjects, subjects with OSAS had a smaller oropharynx (P < 0.05) and larger adenoid (P < 0.01), tonsils (P < 0.05), and retropharyngeal nodes (P < 0.05). The size of lymphoid tissues correlated with severity of OSAS whereas BMI Z-score did not have a modifier effect on these tissues. Subjects with OSAS demonstrated increased size of parapharyngeal fat pads (P < 0.05) and abdominal visceral fat (P < 0.05). The size of these tissues did not correlate with severity of OSAS and BMI Z-score did not have a modifier effect on these tissues.

Conclusions: Upper airway lymphoid hypertrophy is significant in obese children with OSAS. The lack of correlation of lymphoid tissue size with obesity suggests that this hypertrophy is caused by other mechanisms. Although the parapharyngeal fat pads and abdominal visceral fat are larger in obese children with OSAS we could not find a direct association with severity of OSAS or with obesity.

Figure 1.

Upper airway, soft tissues, and mandibular reconstructions. Head and neck surface rendering with three-dimensional reconstructions of the upper airway, soft tissues, and mandible of a subject with obstructive sleep apnea syndrome in various views: lateral (top left), anterior oblique (top right), superior oblique (bottom left) and posterior (bottom right). Airway (light blue), tongue (brown), mandible (white), soft palate (blue), tonsils (yellow), adenoid (magenta), retropharyngeal nodes (red), and deep cervical nodes (green).

Figure 2.

Head and neck fat composition. Surface rendering of the head and neck with three-dimensional reconstructions of the subcutaneous fat (gray) and parapharyngeal fat pads (yellow) of a subject with obstructive sleep apnea syndrome (top left), midtonsillar axial view (top right), coronal view (bottom left), and sagittal view (bottom right).

Figure 3.

Abdominal fat composition. Surface rendering of the abdomen with three-dimensional reconstructions of the subcutaneous fat (gray) and visceral fat (yellow) of a subject with obstructive sleep apnea syndrome (top left), axial view (top right), coronal view (bottom left), and sagittal view (bottom right).

Figure 4.

Correlation between apnea–hypopnea index and combined upper airway lymphoid size (cm³): r = 0.42, P < 0.01.