Tongue Fat and its Relationship to Obstructive Sleep Apnea
Is there an alteration of tongue fat deposition of obese apneics compared to obese subjects without sleep apnea?
This is a case control design with patients primarily recruited from a Sleep Center. In order to find age, gender, and race match obese controls, the apnea-hypopnea index (AHI) was allowed to be <10 events per hour. Up to five apnea-hypopnea events per hour is considered within a normal range for adults without obstructive sleep apnea (OSA). Fat deposition in the tongue was measured with magnetic resonance imaging, using an algorithm to reconstruct tissue volumes to study size and distribution of fat deposits (Ped Radiol 2005:35;601-7). Tongue volume and fat distribution were adjusted for body mass index (BMI), age, gender, and race.
A total of 90 subjects with OSA and 31 without OSA were studied. Patients with OSA were required to have an AHI ≥15 (mean ± standard deviation: AHI of 43.2 ± 27.3 events/hour) and control subjects were required to have an AHI ≤10 (AHI of 4.1 ± 2.7 events/hour). OSA subjects were slightly older (p = 0.004) and also heavier (p < 0.001) than controls. Since controls did not have OSA, the average weight was different: obese apneics (BMI of 39.1 ± 8.3 kg/m2) and controls (BMI of 34.1 ± 4.8 kg/m2). After adjustment for BMI, age, gender, and race, the tongue in subjects with OSA was larger (p = 0.001) and had an increased amount of fat (p = 0.002) compared to control subjects. Differences in regional distribution of fat were observed among obese apneics compared to obese controls.
In this case control design, the authors report an increased tongue volume and deposition of fat at the base of the tongue in apneics compared to controls. Increased tongue fat may begin to explain the relationship between obesity and OSA.
Despite a clear relationship of obesity and OSA, the mechanism by which BMI confers risk for sleep-disordered breathing remains unknown. This preliminary analysis of tongue anatomy is likely to generate further hypotheses. Future studies may likely address how tongue fat impacts extrinsic tongue muscle activity and whether removal of tongue fat (weight loss, tongue exercises, or surgery) may become an alternative treatment of OSA in obese subjects.
Keywords: Body Mass Index, Weight Loss, Tongue, Obesity, Magnetic Resonance Imaging, Sleep Apnea, Obstructive
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