Elsevier

Metabolism

Volume 65, Issue 11, November 2016, Pages 1657-1663
Metabolism

Clinical Science
Fat accumulation in the tongue is associated with male gender, abnormal upper airway patency and whole-body adiposity

https://doi.org/10.1016/j.metabol.2016.08.008Get rights and content

Abstract

Objective

To examine associations between tongue adiposity with upper airway measures, whole-body adiposity and gender. We hypothesized that increased tongue adiposity is higher in males and positively associated with abnormal upper airway measures and whole-body adiposity.

Methods

We studied subjects who underwent whole-body positron emission tomography/computed tomography to obtain tongue attenuation (TA) values and cross-sectional area, pharyngeal length (PL) and mandibular plane to hyoid distance (MPH), as well as abdominal circumference, abdominal subcutaneous and visceral (VAT) adipose tissue areas, neck circumference (NC) and neck adipose tissue area. Metabolic syndrome was determined from available clinical and laboratory data.

Results

We identified 206 patients (104 females, 102 males) with mean age 56 ± 17 years and mean body mass index (BMI) 28 ± 6 kg/m2 (range 16–47 kg/m2). Males had lower TA values (P = 0.0002) and higher upper airway measures (P < 0.0001) independent of age and BMI (P < 0.001). In all subjects, TA was negatively associated with upper airway measures (P < 0.001). TA was negatively associated with body composition parameters (all P < 0.0001), most notably with VAT (r =  0.53) and NC (r =  0.47). TA values were lower in subjects with metabolic syndrome (P < 0.0001).

Conclusion

Increased tongue adiposity is influenced by gender and is associated with abnormal upper airway patency and body composition parameters.

Introduction

Obesity and male gender are significant risk factors for obstructive sleep apnea (OSA) [1], [2], however the mechanisms involved are not completely understood. Prior studies have shown that obesity may lead to upper airway soft tissue enlargement by fat infiltration of the tongue, soft palate and lateral pharyngeal walls [3], [4], [5]. The tongue plays an important role in upper airway patency and increased tongue size and adiposity have been associated with higher risk for OSA [4], [6] (Fig. 1). Importantly, overweight and obese men have significantly higher intermuscular adipose tissue depots in the neck, as well as higher neck circumference [7]. Taken together, these factors may play important roles in a differential risk for OSA between genders.

Abnormal body fat composition parameters such as body mass index (BMI), neck and waist circumference have shown positive associations with upper airway collapsibility measured using the passive pharyngeal critical closing pressure (Pcrit) technique [6]. Further, Pcrit was associated to airway parameters affecting hyoid position such as mandibular plane to hyoid distance (MPH), tongue length, tongue volume, and pharyngeal length, which are affected by tongue adiposity and size [6]. Preliminary evidence suggests that tongue adiposity may parallel ectopic fat accumulation elsewhere, with positive associations between abdominal subcutaneous (SAT) and visceral (VAT) adipose tissue and tongue fat being present among obese subjects [4]. Although evidence suggests links of (a) tongue adiposity with upper airway patency, and (b) tongue adiposity with whole-body adiposity, prior studies have not addressed these findings in a unified cohort of both genders with varied BMI and detailed whole-body composition assessments, including abdominal and neck fat content.

The purpose of this study was to characterize tongue attenuation values as a measure of tongue fat content, upper airway measures and whole-body adiposity using computed tomography (CT) in a cohort with a broad BMI range of both genders. We examined associations between tongue attenuation values, upper airway measures and body composition parameters, and investigated differences between genders and BMI categories. We hypothesized that increased tongue attenuation values reveal higher tongue fat content in males and are positively associated with abnormal upper airway measures and whole-body adiposity.

Section snippets

Materials and Methods

This study was approved by the institutional review board of Partners Health Care and complied with Health Insurance Portability and Accountability Act guidelines, with exemption status for individual informed consent. We performed a retrospective search for consecutive whole-body 18F-fluorodeoxy-glucose (FDG) positron emission tomography and computed tomography (PET/CT) studies obtained in adults (≥ 18 years old) at our institution. Inclusion criteria comprised (a) fasting glucose measured

Clinical Characteristics of Study Subjects

A total of 206 subjects [104 females, 102 males; overall mean (± SD) age of 56 ± 17 years; overall mean BMI of 28 ± 6.0 kg/m2, range 16–47 kg/m2] fulfilled the inclusion criteria outlined above. Included subjects underwent PET/CT for benign etiologies (n = 61) or for follow-up of successfully treated malignancies (n = 145) and had no evidence of active disease at imaging or FDG-avid areas to suggest malignancy. The mean interval between imaging and last treatment was 17 (range 1–120) months.

Mean intervals

Discussion

Our findings using CT attenuation values as a marker for tongue fat content are three-fold: (1) tongue fat content is higher in male subjects; (2) increased tongue fat content is associated with abnormal upper airway measures; (3) tongue fat accumulation parallels whole-body adiposity, with stronger relationships to parameters linked to increased cardiometabolic risk and is higher in subjects with metabolic syndrome.

The tongue is the most important pharyngeal dilator muscle with distinctive

Conclusion

In summary, our study showed that tongue fat deposition as measured by CT attenuation values is associated to abnormal upper airway measures using whole-body cross-sectional imaging. Also these data were associated with abnormal measures of body composition and were significantly influenced by gender.

Author Contributions

IRBG, PG, MAB and MT conceived and carried out the study. IRBG, ELMS, AE and MT conceived the experiments and analyzed data. All authors were involved in writing the paper and had final approval of the submitted and published versions.

Funding

Supported in part by NIH/NIDDKP30DK040561, Nutrition and Obesity Research Center at Harvard.

Disclosure

All authors have no conflicts of interest.

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