• Kate Sutherland, Craig L Phillips, Brendon J Yee, Ronald R Grunstein, and Peter A Cistulli.
• Centre for Sleep Health and Research, Department of Respiratory Medicine, Royal North Shore Hospital, Sydney, Sydney Medical School, University of Sydney, Sydney, Australia.
• Sleep. 2016 Jan 1; 39 (1): 43-9.

Study ObjectivesObesity is the major risk factor for OSA; however, weight loss reduces OSA to a variable extent. We aimed to assess whether size of the maxillomandibular skeletal enclosure influences the relationship between weight loss and OSA reduction.MethodsObese males (≥ 30 kg/m2) with moderate-severe OSA (AHI > 15/h) participating in a 6-mo open-label weight loss program had craniofacial computed tomography (CT) scans before and after weight loss. CT scans were analysed using three-dimensional cephalometry. Maxillomandibular volume was calculated from skeletal landmarks on the mandible (condyle, gonion, menton) and maxilla (anterior nasal spine). Multiple regression analysis was used to test for moderating effects of maxillomandibular volume on relationship between changes in weight and apnea-hypopnea index (AHI).ResultsFifty-two men (age 44.3 ± 8.8 y, AHI 42.9 ± 21.3 events/h, body mass index [BMI] 34.0 ± 2.7 kg/m2) had 7.4 ± 4.1% weight loss and 34.1 ± 32.4% AHI reduction at 6 months. BMI reduction modestly predicted AHI change (r2 = 0.17, P = 0.002). The interaction term of maxillomandibular volume and BMI change was a predictor of OSA improvement (P = 0.03), indicating maxillomandibular volume moderates this relationship. Subgroup analyses of patients by small, medium, and large maxillomandibular volume showed a strong correlation between weight loss and OSA improvement only in the small volume group (r = 0.654, P = 0.004). There was no relationship evident in those with large maxillomandibular volume (r = 0.05, P = 0.9).ConclusionMaxillomandibular volume influences the relationship between weight loss and OSA improvement with an effect on AHI more evident in those with a smaller craniofacial skeleton.© 2016 Associated Professional Sleep Societies, LLC.

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