Association Between Oral Function and Underweight in Dental Outpatients Under Regular Maintenance: A Cross-Sectional Study

Objective This study aimed to evaluate the prevalence of oral hypofunction among dental maintenance outpatients aged over 50 years who had completed dental treatment at least three months before and to explore the relationship among oral hypofunction, age, and underweight. Background Recently, the relationship between oral function and general health, such as frailty or sarcopenia, through the mechanism of declining nutritional status, has been the focus of research. Improving oral function, such as general dental treatment, may prevent deterioration or improve overall health, but the causal relationship has not yet been fully clarified. It is useful how often the general dentist might encounter subjects with oral hypofunction in regular maintenance patients or how oral hypofunction could predict present underweight status. Materials and methods This cross-sectional study enrolled 107 subjects (mean age: 72.9 ± 9.2 years, 40.2% men). Oral hypofunction tests and body mass index (BMI) were used as indicators of oral function and nutrition status, respectively. Underweight was defined based on the BMI cut-off values specified in the Global Leadership Initiative on Malnutrition (GLIM) criteria for Asians. Other patient characteristics, such as medical history, the number of teeth, and functional tooth units (FTUs), were collected from the patients' charts. The participants were classified into three groups: middle-aged (50-64 years), early older adult (65-74 years), and late older adult (≥75 years). Associations among oral hypofunction, underweight, and age were evaluated using two-way ANOVA, with additional analyses performed using general linear models (GLM) to account for potential confounders. Results The overall prevalence of oral hypofunction was 50.5%, and 48.1% of the participants in the nonunderweight group (n = 81) exhibited oral hypofunction. The oral hypofunction group was significantly older than the nonoral hypofunction group (75.5 ± 7.4 versus 70.3 ± 10.1 years, p < 0.05). No significant differences in BMI status were observed among the three age groups, although functions of oral hygiene status (tongue coating index {TCI}) and oral diadochokinesis (ODK) (/ta/ and /ka/) had significant differences in some parts of the age groups. In multivariable-adjusted general linear models, age group remained significantly associated with oral diadochokinesis, and a significant interaction between age group and underweight status was observed for tongue coating index. Conclusion Approximately half of the dental outpatients in the maintenance phase in this study exhibited oral hypofunction. Oral hypofunction was significantly observed in elderly people in the dental maintenance phase. Although it could not be detected as a significant uniform association between oral hypofunction and underweight, the small underweight group limits our ability to rule out a clinically meaningful relationship.