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Muscle strength and function are generally positively correlated with muscle quantity and negatively correlated with muscle quality; however, the tongue shows a unique tendency, different from limb muscles. The relationship between the characteristics of each part of the tongue, muscle strength and function, and systemic factors has been unclear. The aim of the study was to investigate the relationship between cross-sectional area (CSA) and echo intensity (EI) of the middle and base of the tongue and swallowing, articulation function, and body composition. Eighty-nine healthy individuals were included in this cross-sectional study. Swallowing was assessed using tongue pressure (TP) and jaw opening force (JOF) as they indicate swallowing-related muscle strength. Articulation function was evaluated through oral diadochokinesis (ODK). Bioelectrical impedance analysis was performed for body composition. CSAs and EIs of the middle and base of the tongue were measured using ultrasound. Multiple regression analysis was used to examine the relationship between the characteristics of the tongue, swallowing-related muscle strength, and ODK. In multiple regression analysis with TP as the dependent variable, age (β = - 0.22, P 0.01) and CSA of the middle part (β = 0.02, P 0.01) were significant explanatory variables. In multiple regression analysis with JOF as the dependent variable, sex (β = - 2.76, P 0.01) and CSA of the base (β = - 0.004, P 0.05) were significant explanatory variables. Multiple regression analysis with articulation function as the dependent variable did not yield significant results. The CSA of the tongue is a better indicator of swallowing-related muscle strength than EI. Ultrasonography may be used for assessing swallowing-related muscle strength.

Many screening tests for dysphagia can be given at bedside. However, they cannot accurately screen for silent aspiration (SA). We studied the usefulness of a cough test to screen for SA and combined it with the modified water swallowing test (MWST) to make an accurate screening system. Patients suspected of dysphagia (N = 204) were administered a cough test and underwent videofluorography (VF) or videoendoscopy (VE). Sensitivity of the cough test for detection of SA was 0.87 with specificity of 0.89. Of these 204 patients, 107 were also administered the MWST. Fifty-five were evaluated as normal by the screening system, 49 of whom were evaluated as normal by VF or VE. Sixteen were evaluated as "SA suspected" by the screening system; seven of them were normal, and seven were evaluated as having SA by VF or VE. Nineteen were evaluated as aspirating with cough, 14 of whom had aspiration with cough as shown by VF or VE. Seventeen were evaluated as having SA, 15 of whom had SA shown by VF or VE. The cough test was useful in screening for SA. Moreover, a screening system that included MWST and a cough test could accurately distinguish between the healthy who were safe in swallowing and SA patients who were unsafe.