Factors Affecting Mandibular Movement During Mastication in Nursing Home Residents: A Two-Year Follow-Up Study

Background/Objectives: Declining masticatory function affects dietary variety, nutritional status, cognitive function, and health. Although factors related to chewing ability have been reported, the causes of temporal changes in masticatory kinematics in older adults remain unclear because prospective longitudinal data remain limited. Objectives: This follow-up study investigated factors associated with changes in masticatory movement in older adults requiring long-term care. Methods: Participants were 42 older adults residing in long-term care facilities. Survey items included mandibular kinematic data during rice cracker chewing and variables related to chewing, and the same assessment was performed two years after baseline. Relationships between changes in masticatory movement and other variables were examined, and factors associated with masticatory movement were identified using a linear mixed model (LMM). Results: A change in the number of cycles was significantly associated with the rate of change in the appendicular skeletal muscle mass index (ASMI). The rates of change in the number of linear motions and circular motion frequency were significantly associated with changes in the ABC Dementia Scale (ABC-DS). In the LMM results, cycle frequency remained associated with ASMI after adjustment for confounding factors, and both the number of circular motions and circular motion frequency were associated with ABC-DS. Conclusions: The findings suggest that masticatory movement in older adults requiring long-term care is influenced by skeletal muscle mass and cognitive function. In care facilities, interventions to maintain these factors are essential to help prevent dietary texture modifications among residents, while supporting nutrition, oral function, and health in this population.