A High Masticatory Muscle Tone Predicts the Risk of Malnutrition and Frailty in Inpatient Older Adults: A Cross-Sectional Study

Introduction: The prevalence of malnutrition among inpatient older adults is as high as 20∼50%. Masticatory performance is known to affect the nutritional status of individuals. However, an objective measurement to reflect the real status of masticatory muscle performance is lacking at the bedside. Methods: This pilot study analyzed the masticatory performance using surface electromyography (sEMG) of masticatory muscles that measures both muscle strength and muscle tone at the bedside. The nutritional status was measured using the Mini Nutritional Assessment tool. The handgrip strength was measured using a hand dynamometer. The statistical data were analyzed using SPSS 25 software. Results: The data revealed that female inpatient older adults more frequently had substandard handgrip strength (p = 0.028), an at-risk and poor nutritional status (p = 0.005), and a higher masseter muscle tone (p = 0.024). Inpatient older adults with an at-risk and poor nutritional status had an older age (p = 0.016), lower handgrip strength (p = 0.001), and higher average masseter muscle tone (p = 0.01). A high masseter muscle tone predicted the risk of having an at-risk and poor nutritional status. The at-risk or poor nutritional status predicted having a substandard handgrip strength by 5-fold. Conclusions: A high masticatory muscle tone predicts malnutrition and frailty. Medical professionals should combat masticatory dysfunction-induced malnutrition by detecting masticatory muscle performance using sEMG and referring patients to dental professionals. Additionally, encouraging inpatient older adults to perform oral motor exercise is recommended.