Age-related changes in swallowing muscle intramuscular adipose tissue deposition and related factors

Objectives: To investigate age-related changes in the intramuscular adipose tissue (IAT) of the tongue and gen-iohyoid muscle (GHM) and associated factors. Design: Exploratory cross-sectional study. Setting and participants: This study included 89 participants recruited from a health survey, which included 38 younger adults (age range, 20-63 years) and 51 older adults (age range, 65-87 years). Measurements: Age, body mass index, body fat, lean body mass, skeletal muscle mass index, trunk muscle mass index, tongue pressure, jaw opening force, and oral diadochokinesis were assessed. The cross-sectional area (CSA) and echo intensity (EI) of the tongue and GHM were measured using ultrasonography. IAT was assessed according to EI values. The factors related to the IAT of each muscle were examined using multiple regression analysis. We also investigated the correlation of IAT with factors related to oral function and systemic and morphological factors. Results: Neither the EI of the tongue nor that of the GHM had a significant correlation with factors related to oral function and systemic factors. In the multiple regression analysis, significant explanatory variables for EI of the tongue and GHM were age (13 = 0.14, P = 0.019; tongue and 13 = 0.13, P = 0.017; GHM) and the CSA of each muscle (13 =-0.01, P = 0.042; tongue and 13 =-0.04, P = 0.003; GHM). EI was positively associated with age and negatively associated with muscle CSA. Conclusion: Age-related changes in the IAT show the same trend for both the tongue and GHM, unlike age-related changes in muscle mass. The IATs of the tongue and GHM were not significantly correlated with oral function and systemic factors. Therefore, EI may not be a useful index for the functional evaluation of the tongue and GHM.