Obesity is a risk factor for many health problems, but a new Penn Medicine study published this month in the journal Sleep suggests having a larger tongue with increased levels of fat may be a sign of obstructive sleep apnea (OSA) in obese adults.
The researchers examined tongue fat in 31 obese adults who had OSA and 90 obese adults without the condition. All subjects underwent magnetic resonance imaging and the size and distribution of upper airway fat deposits in their tongue and upper airway muscles measured.
"Previous studies showed that the human tongue has a high percentage of fat, and that tongue fat and tongue weight were positively correlated with the degree of obesity," said study senior author Richard J. Schwab, MD, professor of Medicine in Penn's Perelman School of Medicine and member of the Center for Sleep and Circadian Neurobiology. "This is the first study that examined OSA patients and found higher fat deposits in obstructive sleep apnea patients than in those without OSA."
The data also showed a correlation between tongue fat volume and sleep apnea severity, and with body mass index. The researchers believe that increased tongue fat may explain the pathogenic relationship between obesity and sleep apnea.
Adults with a body mass index of 30 or higher are considered obese. The latest Centers for Disease Control and Prevention survey of nationally representative data in 2011 and 2012 reported that nearly 35 percent of U.S. adults - 78.6 million people - are obese. OSA affects more than 15 million adult Americans. The number of OSA cases is rising, mirroring the increasing weight of the average individual.
Although obesity is the strongest risk factor for development of OSA, the ways that obesity confers risk for OSA are unknown. The researchers believe the increase in fat not only increases tongue size, but also decreases tongue force and hinders the tongue from properly functioning as an upper airway dilator muscle, which can lead to apneas during sleep.
Study authors note that further studies are needed to determine if weight loss decreases tongue fat, and whether improvements in sleep-disordered breathing are associated with changes in tongue fat.
Other Penn coauthors are Andrew M. Kim, Brendan T. Keenan, Nicholas Jackson, Eugenia L. Chan, Bethany Staley, Harish Poptani, Drew A. Torigian, and Allan I. Pack.
The study was supported by funding from the National Institutes of Health (R01HL089447 and P01HL094307). For more information, see the American Academy of Sleep Medicine press release.