Using magnetic resonance imaging (MRI) to measure the effect of weight loss on the upper airway in obese patients, the study, published in the American Journal of Respiratory and Critical Care Medicine, found that reducing tongue fat is a primary factor in lessening the severity of OSA.
"Most clinic, and even experts in the sleep apnea world, have not typically focused on fat in the tongue for treating sleep apnea," said study researcher Richard Schwab from University of Pennsylvania in the US.
"Now that we know tongue fat is a risk factor and that sleep apnea improves when tongue fat is reduced, we have established a unique therapeutic target that we've never had before," Schwab added.
A 2014 study led by Schwab compared obese patients with and without sleep apnea, and found that the participants with the condition had significantly larger tongues and a higher percentage of tongue fat when compared to those without sleep apnea.
The researchers next step was to determine if reducing tongue fat would improve symptoms and to further examine cause and effect.
The new study included 67 participants with mild to severe obstructive sleep apnea who were obese those with a body mass index greater than 30.
Through diet or weight loss surgery, the patients lost nearly 10 per cent of their body weight, on average, over six months.
Overall, the participants' sleep apnea scores improved by 31 per cent after the weight loss intervention, as measured by a sleep study.
Before and after the weight loss intervention, the study participants underwent MRI scans to both their pharynx as well as their abdomens.
Then, using a statistical analysis, the research team quantified changes between overall weight loss and reductions to the volumes of the upper airway structures to determine which structures led to the improvement in sleep apnea.
The team found that a reduction in tongue fat volume was the primary link between weight loss and sleep apnea improvement.
The study also found that weight loss resulted in reduced pterygoid (a jaw muscle that controls chewing) and pharyngeal lateral wall (muscles on the sides of the airway) volumes.
Both these changes also improved sleep apnea, but not to the same extent as the reduction in tongue fat.
The authors believe that tongue fat is a potential new therapeutic target for improving sleep apnea.
( With inputs from IANS )