Impact of occlusal force on decline in body mass index among older Japanese adults: Finding from the SONIC study

Objectives To determine any independent influence of occlusal force and of number of natural teeth on decline in body mass index (BMI) among older Japanese adults. Design Longitudinal study over a 3- to 6-year period. Setting Urban and rural area in Japan. Participants Independently living Japanese adults aged 69-71 years and 79-81 years at baseline. This analysis excluded participants who were defined as underweight at baseline. Measurements Information was collected on age, gender, occlusal force, the number of teeth, BMI, socioeconomic factors, medical history, the number of daily prescription medications, cognitive function, depressive symptoms, hand grip strength, and physical function. Maximal occlusal force was measured with a pressure-sensitive sheet. Nutritional status was assessed using BMI, and participants with BMI <21.5 were defined as underweight. Then, they were divided into two groups: a "BMI declined" group who were defined as underweight at either 3- or 6-year follow-up survey, and a "BMI maintained" group who were not defined as underweight at both follow-up surveys. Logistic generalized estimating equation (GEE) models were used to assess the effect of occlusal force and the number of teeth at baseline on decline in BMI over 3 or 6 years, after adjusting for possible covariates associated with nutritional status. Results The final analysis included 704 participants. Eighty-six (12.2%) participants were classified into the BMI declined group. Logistic GEE models showed that the number of teeth was not significantly associated with decline in BMI. However, occlusal force was significantly associated with decline in BMI (odds ratio = 0.90, 95% confidence interval = 0.83-0.97) after adjusting for covariates. Conclusion Participants with lower occlusal force were more likely to be in the BMI less than 21.5 kg/m(2). The findings suggest that to prevent decline in oral function is important to maintain nutritional status.