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Aim Previous studies on the association between intraoral conditions and mortality in community‐dwelling older individuals reported that fewer present teeth (PT) are significant risk factors for mortality. However, how the number of PT relative to the number of functional teeth (FT), including both present and rehabilitated teeth, influences mortality has not been investigated fully. This study examined the impact of the number of FT on mortality among community‐dwelling Japanese older adults. Methods This study was a retrospective, observational and population‐based follow‐up study, which examined 1188 older individuals who participated in an annual geriatric health examination from 2009 to 2015. The average follow‐up period was 1697.0 ± 774.5 days. The primary outcome was all‐cause mortality at follow‐up. The numbers of PT and FT of each participant were counted during an oral examination. In addition, demographics, clinical variables, blood nutrient markers, physical functions and perceived masticatory function were measured. Results Kaplan–Meier analysis, followed by a log‐rank test, revealed that fewer PT (P < 0.001) and FT (P = 0.002) were significantly associated with a reduced survival rate. Cox's proportional hazard analysis indicated that the number of FT, but not the number of PT, was a significant independent mortality risk factor after adjusting for demographics, clinical variables, nutrient markers and physical functioning (P = 0.036, hazard ratio: 2.089). Conclusions Current results suggest that the number of FT more strongly predicts all‐cause mortality than the number of PT among community‐dwelling older adults. Further studies are necessary to consider the confounding of socioeconomic status and disability status. Geriatr Gerontol Int 2020; ••: ••–••.

Aim To examine the relationship between the number of present and functional teeth at baseline and future incidence of loss of independence. Methods Participants were community‐dwelling older individuals who participated in a comprehensive geriatric health examination conducted in Kusatsu town, Japan, between 2009 and 2015. The primary endpoint was the incidence of loss of independence among participants, defined as the first certification of long‐term care insurance in Japan. The numbers of present and functional teeth at baseline were determined via an oral examination. Demographics, clinical variables (e.g., history of chronic diseases and psychosocial factors), blood nutritional markers, physical functions, and perceived masticatory function were assessed. Results This study included 1121 individuals, and 205 individuals suffered from loss of independence during the follow‐up period. Kaplan–Meier estimates of loss of independence for participants with smaller numbers of present and functional teeth were significantly greater than for those with larger numbers of teeth. Cox proportional hazard analyses indicated that a smaller number of present teeth was not a significant risk factor after adjusting for demographic characteristics. However, the number of functional teeth was a significant risk factor after the adjustment (hazard ratio: 1.975 [1.168–3.340]). Additionally, higher hazard ratios were observed in other adjusted models, but they were not statistically significant. Conclusions The number of functional teeth may be more closely related to the future incidence of loss of independence than the number of present teeth. This novel finding suggests that prosthodontic rehabilitation for tooth loss possibly prevents the future incidence of this life‐event. Geriatr Gerontol Int 2022; 22: 1032–1039.

Maintenance and improvement of masticatory function in nursing care elderly persons (NC) is an important issue, and it is speculated that sarcopenia is related to declining masticatory function. The decrease in skeletal muscle index (SMI), a major diagnostic criterion for sarcopenia, has been reported to be associated with swallowing function in NC. However, the relationship between SMI and masticatory function is unknown. Therefore, we investigated the relationship between masseter muscle thickness(MMT)and SMI, with the aim of examining the specific relationship between decreased masticatory function and sarcopenia in NC. MMT and SMI were measured by ultrasonography and bioelectrical impedance analysis in 275 NC participants in Omori Town, Yokote City, Akita Prefecture in the Tohoku region in Japan. Cognitive functions measured from all participants using questionnaire. Participants were classified into low-MMT or high-MMT group based on the median of each of MMT, and SMI and related items in each gender. In addition, to examine the factors related to MMT, logistic regression analysis was conducted by entering age, sex, SMI, nutrition status, severity of dementia, and other items as explanatory variables and MMT as objective variable. SMI in high-MMT group were significantly higher than low-MMT group (high-MMT: 4.8 ± 1.4 kg/m 2 , low-MMT: 4.4 ± 1.4 kg/m 2 , P = 0.010). Furthermore, logistic regression analysis indicated that SMI were significantly associated with a MMT(Odds Ratio=0.83, 95% Confidence Interval=0.69-0.99, P=0.049). Our result suggested that the mass of the masseter muscles decreased with NC due to sarcopenia, possibly contributing to a decrease in masticatory function.

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.