Ultrasonography to detect age-related changes in swallowing muscles

Purpose: Sarcopenia of swallowing muscles is a potential cause of dysphagia. We investigated age-related changes in mass and quality of swallowing muscles by ultrasonography as a non-invasive and convenient examination in subjects without dysphagia. Methods: A total of 104 subjects (34 males, 70 females) participated in this study. Age, physical status, and mass and strength of skeletal and swallowing muscles were investigated. Ultrasonography was performed to measure cross-sectional area and brightness of the geniohyoid muscle as a swallowing muscle. Calf circumference was measured to evaluate skeletal muscle mass. Hand grip strength was measured to evaluate skeletal muscle strength. Subjects were divided into two groups: young (< 65 years old) and old (≥ 65 years old). We performed univariate and multivariate analyses to analyze the differences between the groups. Results: The number of subjects in the young group was 35, and 69 in the old group. The mean ± SD of measurements in each group was as follows (young/old): age, 35.4 ± 13.9/74.5 ± 5.5 years old; calf circumference, 37.4 ± 4.1/33.9 ± 2.7 cm (p < 0.001); hand grip strength, 35.6 ± 10.2/25.8 ± 7.6 kg (p < 0.001); cross-sectional area of geniohyoid muscle, 229.5 ± 52.2/174.1 ± 40.7 mm² (p < 0.001); and brightness of geniohyoid muscle, 46.6 ± 11.1/59.6 ± 10.8 (p < 0.001). The old group had a significantly smaller geniohyoid muscle area and significantly greater geniohyoid muscle brightness than the young group (p < 0.01). Age and calf circumference were independent explanatory factors for geniohyoid muscle area (p < 0.01). Age and sex were independent explanatory factors for geniohyoid muscle brightness (p < 0.01). Conclusions: Ultrasonography revealed a smaller area and greater brightness, which suggested smaller mass and greater infiltration of fat, in the geniohyoid muscle in old people than in young people.