Penn Medicine study suggests tongue could be new target for treating sleep apnea

Improvements in sleep apnea symptoms appear to be linked to the reduction of fat in the tongue, according to new research by the Perelman School of Medicine at the University of Pennsylvania in Philadelphia and published in the American Journal of Respiratory and Critical Care Medicine.

Using magnetic resonance imaging (MRI) to measure the effect of weight loss on the upper airway in obese patients, researchers found that reducing tongue fat is a primary factor in lessening the severity of sleep apnea.

The study included 67 participants with mild to severe obstructive sleep apnea who were obese, those with a body mass index greater than 30.0. Through diet or weight loss surgery, the patients lost nearly 10 percent of their body weight, on average, over six months. Overall, the participants' sleep apnea scores improved by 31 percent 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.

Twenty-two million Americans suffer from sleep apnea, a serious health condition in which breathing repeatedly stops and starts, causing patients to wake up randomly throughout their sleep cycles. The condition, which is usually marked by loud snoring, can increase risk for high blood pressure and stroke. While obesity is the primary risk factor for developing sleep apnea, there are other causes, such as having large tonsils or a recessed jaw.

Continuous positive airway pressure (CPAP) machines improves sleep apnea in about 75 percent of patients, studies suggest, but for the other 25 percent, those who may have trouble tolerating the machine, alternative treatment options, such as oral appliances or upper airway surgery, are more complicated.

The authors believe that tongue fat is a potential new therapeutic target for improving sleep apnea. They suggest that future studies could be designed to explore whether certain low-fat diets are better than others in reducing tongue fat and whether cold therapies, like those used to reduce stomach fat, might be applied to reducing tongue fat. However, these types of interventions have not yet been tested, said Richard Schwab, MD, lead author and chief of Sleep Medicine.

"Primary care doctors, and perhaps even dentists, should be asking about snoring and sleepiness in all patients, even those who have a normal body mass index,” he said in a statement. “Based on our data, they may also be at risk for sleep apnea.”