LAUSR

RATIONALE Obesity is the primary risk factor for sleep apnea (OSA). Tongue fat is increased in obese persons with OSA, and may explain the relationship between obesity and OSA. Weight loss improves OSA, but the mechanism is unknown. OBJECTIVES To determine the effect of weight loss on UA anatomy in persons with obesity and OSA. We hypothesized that weight loss would decrease soft tissue volumes and tongue fat and these changes would correlate with reductions in apnea-hypopnea index (AHI). METHODS Sixty-seven individuals with obesity and OSA (AHI≥10 events/hour) underwent a sleep study and UA and abdominal magnetic resonance imaging (MRI) before and after a weight loss intervention (intensive lifestyle modification or bariatric surgery). Airway sizes and soft tissue, tongue fat, and abdominal fat volumes were quantified. Associations between weight loss and changes in these structures, and relationships to AHI changes, were examined. MEASUREMENTS AND MAIN RESULTS Weight loss was significantly associated with reductions in tongue fat, pterygoid and total lateral wall volumes. Reductions in tongue fat were strongly correlated with reductions in AHI (rho=0.62, p<0.0001); results remained after controlling for weight loss (rho=0.37, p=0.014). Mediation analyses indicated that reduction in tongue fat volume was the primary mediator of the relationship between weight loss and AHI improvement. CONCLUSIONS Weight loss reduced volumes of several UA soft tissues in persons with obesity and OSA. Improved AHI with weight loss was mediated by reductions in tongue fat. New treatments that reduce tongue fat should be considered for patients with OSA.