18The term "oral frailty" reflects the fact that oral health is associated with 19 physical frailty and mortality. Tongue thickness measurement is one of the evaluations for 20 swallowing function. The aim of this study was to investigate the relationship between tongue 21 thickness and tongue pressure in the Japanese elderly. We evaluated 254 elderly patients; all 22 the participants underwent tongue ultrasonography and tongue pressure measurement. To 23 determine tongue thickness, we measured the vertical distance from the surface of the 24 mylohyoid muscle to the tongue dorsum using ultrasonography. Result analyses revealed that 25 tongue thickness was linearly associated with tongue pressure in both sexes. In male 26 participants, dyslipidemia, lower leg circumference, and tongue pressure were independently 27 significantly associated with tongue thickness. In female participants, body mass index and 28 tongue pressure were independently significantly associated with tongue thickness. Tongue 29 thickness was significantly decreased by age for both men and women. The optimal cutoff for 30 tongue thickness to predict the tongue pressure of < 20 kPa was 41.3 mm in males, and 39.3 31 mm in females. In the Japanese elderly, tongue thickness using ultrasonography is associated 32 with tongue pressure. Tongue thickness and tongue pressure, which are sensitive markers for 33 oral frailty, decrease in aging. The tongue ultrasonography provides a less invasive technique 34 for determining tongue thickness and related aspiration risks for elderly patients. 35

The term "oral frailty" reflects the fact that oral health is associated with physical frailty and mortality. The gold standard methods for evaluating the swallowing function have several problems, including the need for specialized equipment, the risk of radiation exposure and aspiration, and general physicians not possessing the requisite training to perform the examination. Hence, several simple and non-invasive techniques have been developed for evaluating swallowing function, such as those for measuring tongue pressure and tongue thickness. The aim of this study was to investigate the relationship between tongue thickness ultrasonography and tongue pressure in the Japanese elderly. We evaluated 254 elderly patients, who underwent tongue ultrasonography and tongue pressure measurement. To determine tongue thickness, we measured the vertical distance from the surface of the mylohyoid muscle to the tongue dorsum using ultrasonography. The results of the analyses revealed that tongue thickness was linearly associated with tongue pressure in both sexes. In male participants, dyslipidemia, lower leg circumference, and tongue pressure were independently and significantly associated with tongue thickness. In female participants, body mass index and tongue pressure were independently and significantly associated with tongue thickness. The optimal cutoff for tongue thickness to predict the tongue pressure of < 20 kPa was 41.3 mm in males, and 39.3 mm in females. In the Japanese elderly, tongue thickness using ultrasonography is associated with tongue pressure. Tongue thickness and tongue pressure, which are sensitive markers for oral frailty, decrease with age. We conclude that tongue ultrasonography provides a less invasive technique for determining tongue thickness and predicts oral frailty for elderly patients.