Interrelationships among whole-body skeletal muscle mass, masseter muscle mass, oral function, and dentition status in older Japanese adults.

BACKGROUND: Generalized loss of skeletal muscle mass (SMM) may modulate or otherwise affect the loss of masseter muscle mass and be responsible for low masseter muscle performance and strength (i.e., low oral function). Moreover, dentition status can affect oral function independent of the muscle state. This cross-sectional study aimed to simultaneously investigate the relationships among whole-body SMM, masseter muscle mass, oral function (masseter muscle performance and strength), and dentition status in 1349 Japanese adults (mean age = 73.6 years). METHODS: We determined the estimated masseter muscle mass (e-MMM) based on morphological measurements of the masseter muscle. Masseter muscle performance was assessed via masticatory performance evaluation scores using gum, and strength was assessed as the maximal occlusal force. Dentition status was assessed as the number of functional teeth. SMM was measured by bioelectrical impedance analysis. Structural equation modeling stratified by sex was employed to investigate associations among SMM, e-MMM, gum score, occlusal force, and number of functional teeth. RESULTS: The direct path from SMM to e-MMM was statistically significant, as was the direct path from e-MMM to oral function (gum score and maximum occlusal force) for both sexes. We additionally confirmed that SMM indirectly affected gum score and maximum occlusal force via e-MMM (men; standardized coefficient [95% CI] = 3.64 [1.31 to 5.96] for maximum occlusal force and 0.01 [0.01 to 0.02] for gum score, women; 2.01 [0.38 to 3.81] for maximum occlusal force and 0.01 [0.002 to 0.01] for gum score). The number of functional teeth had direct effects on e-MMM, gum score, and maximum occlusal force. CONCLUSIONS: Low SMM was significantly indirectly associated with poor oral function through a low masseter muscle mass, and dentition status was independently associated with oral function.

[Effect of an oral function improvement program based on remote intervention].

AIM: We studied the effect of an oral function improvement program based on the remote intervention by non-specialist assistant as coordinators, who played the role of intermediary between the participants and dental hygienists. METHODS: Among senior citizens aged 65 or older living on pacific islands within the area of greater Tokyo (Tosyobu), 55 people participated in this study. Dental hygienists educated the coordinators beforehand. The participants were evaluated on mastication ability, swallowing ability and oral function-related quality of life (QOL) by dental hygienists before and after the program. The participants did the oral health improvement program every day at home, using materials provided by the dental hygienists. The coordinators reported compliance and questions about the oral function improvement program to the dental hygienists by fax once a week. The dental hygienists replied with technical advice on continuing the exercises, to coordinators by fax. RESULTS: The summed time of 3 times of repetitive saliva swallowing test was significantly reduced (p<0.01). The oral diadochokinesis of articulation function was significantly improved (p<0.01). The color of the mastication function assessment gum significantly improved (p<0.01). Scores on the general oral health assessment index, an index of oral-related QOL, also significantly increased (p<0.05). The items about dental hygiene also improved on the same index. CONCLUSION: Oral function was improved in terms of swallowing, articulation, chewing, hygiene and QOL. This research suggests that the program, in which dental hygienists are involved in a remote way through coordinators, and offer services for oral function improvement, can be effective to improve the oral function of the elderly.

Relation between knee extension torque and occlusal force in community-dwelling elderly adults.

The relation between occlusal force and general motor ability induced by lower-limb musculature is unclear. To identify indicators of oral and lower-limb muscle weakness, this study examined the relation between masticatory muscle strength and lower limb muscle force in 742 community-dwelling elderly adults (315 men and 427 women, mean age 73.3 ± 5.5 years) living in Itabashi ward, Tokyo. Multiple regression analysis of the relation between occlusal force and knee extension torque, in relation to age and sex, showed a significant correlation between the two variables (r = 0.348, P < 0.001), which indicates that occlusal force is a determinant of knee extension torque. Occlusal force remained significantly correlated with knee extension torque after adjustment for factors known to be related to the latter. In conclusion, chewing function and lower-limb motor function were significantly correlated and thus might be indicators of muscle weakness in elderly adults.