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Tongue size may trigger obstructive sleep apnea in obese adults
Tongue volume and deposition of fat at the base of the tongue are increased in patients with obstructive sleep apnea than those without, according to research published in Sleep.
The increased tongue fat could partly explain the relationship between obesity and obstructive sleep apnea, according to University of Pennsylvania researchers.
“This is the first study to show that fat deposits are increased in the tongue in patients with obesity with obstructive sleep apnea,” Richard J. Schwab, MD, DABSM, of the Penn Sleep Center, said in a press release. “This work provides evidence of a novel pathogenic mechanism explaining the relationship between obstructive sleep apnea and obesity.”
Richard J. Schwab
In a case-control design, Schwab, along with Andrew M. Kim, BS, of the Penn Sleep Center, and colleagues examined tongue fat in 31 patients with obesity (apnea-hypopnea index, 4.1 events/hour) and 90 patients with obesity and obstructive sleep apnea (apnea-hypopnea index, 43.2 events/hour). The investigators repeated the analyses in a subsample of 18 gender-, race-, age- and BMI-matched case-control pairs.
Patients underwent an MRI with three-point Dixon imaging. Volumetric reconstruction algorithms were used to assess size and distribution of upper airway fat deposits in the tongue and masseter muscles. Adjustments were made for age, BMI, gender and race.
Compared with controls, patients with obstructive sleep apnea had significantly larger tongues (P=.001) and an increased amount of fat (P=.002) after adjusting for potential confounders. Similar results were seen in the matched sample. Regional differences in fat distribution, with larger fat deposits at the base of the tongue, were observed between patients with obstructive sleep apnea and those without.
“We believe this increase in fat deposition not only enlarges tongue size, but also may decrease tongue force and hinder the tongue from properly functioning as an upper airway dilator muscle,” the researchers wrote. “Additionally, tongue size and tongue fat correlated with apnea-hypopnea index.”
The researchers noted that further investigation is needed to determine whether weight loss affects tongue fat and whether improvements in sleep-disordered breathing are associated.
In an accompanying editorial, Eric J. Kezirian, MD, MPH, of the University of Southern California, wrote that further investigation is warranted, particularly in individuals with normal or low BMI, and he expressed excitement about the potential for clinical practice.
“Fat deposition within the tongue — and potentially other structures surrounding the upper airway — may transform our understanding of the link between weight gain and obstructive sleep apnea, with wide-ranging implications for diagnosis and treatment,” Kezirian said.
Disclosure: This study was supported by NIH grants.
Perspective
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This study of obese adults is the first to show that those who have obstructive sleep apnea have a significantly larger tongue with a higher percentage of fat than obese controls. For many years, many clinicians have suspected this to be the case, carefully noting findings such as dental ridging on the tongue as a clue to this finding.
This study adds some information about potential mechanisms. In addition to enlarging the size of the tongue, increased tongue fat may impair the functioning of the muscles that attach the tongue to bone, preventing these muscles from positioning the tongue away from the airway. Future studies could establish the effectiveness of removing tongue fat through weight loss, upper airway exercises or surgery as a potential treatment for sleep apnea.
Effective identification and treatment of sleep apnea is essential to optimally manage other conditions associated with this chronic disease, including high blood pressure, heart disease, type 2 diabetes, stroke and depression. In addition to excess body weight — as the major predisposing factor for obstructive sleep apnea — tongue size is one of the physical features that should be evaluated by a physician when screening obese patients to determine their risk for obstructive sleep apnea. Common warning signs for sleep apnea include snoring and choking, gasping, or silent breathing pauses during sleep.