Objectives/hypothesis: Obesity as measured by body mass index (BMI) has been shown to correlate with incidence and severity of sleep disordered breathing (SDB), but the actual mechanism underlying this relationship has not been defined. Pharyngeal obstruction from posterior displacement of a large, fat laden tongue is one mechanism that may explain this link. The objective of this study is to characterize the fat content within the tongue and then to determine whether tongue weight and percent of fat correlate with BMI and other metrics of obesity.
Study design: This is a cross-sectional anatomic study performed at autopsy in 121 consecutive medical examiner cases.
Methods: Tongues were harvested, weighed, and sectioned. A standardized photograph was taken of each tongue in the midsagittal plane. The image was imported into ImageJ (NIH) and then digitally analyzed to estimate fat distribution and percent within the tongue. The measurements were divided into age and sex subsets and then examined for correlation with height, weight, BMI, organ weight, and abdominal subcutaneous fat thickness.
Results: This study includes data from 88 males, 27 females, and 6 children. The average tongue weight for males was 99 g, range 71 to 143 g; for females, 79 g, range 51 to 135 g; and for children, (mean age 4 yr) 38 g, range 15 to 81 g. Tongue weight correlated with BMI (r = 0.6, P < .0001). Percent of fat in the posterior tongue averaged 30 +/- 12% and correlated with BMI (r = 0.5, P < .0001) for both men and women. Percent of fat in the anterior tongue averaged 10 +/- 5% and correlated with BMI for males (P < .001). Anterior tongue fat percent did not correlate with BMI in females.
Conclusion: Increase in tongue weight and percentage of fat, and therefore tongue volume, may explain why patients with weight gain have higher rates of SDB. Tongue weight, fat, and volume may also correlate with and explain Mallampati grades.