Association Between Oral Frailty and Body Mass Index in Late-Stage Older Adults Stratified by Sarcopenia Status

Objectives: Oral frailty is associated with sarcopenia and underweight; however, its relationship with sarcopenic obesity remains unclear. This cross-sectional study investigated the associations between oral frailty and body mass index (BMI) categories (underweight/obesity), stratified by sarcopenia status. Methods: Data were obtained from dental checkups for 3829 older adults in Tottori, Japan (1489 men and 2340 women, mean age: 80.1 ± 4.3 years). Participants were divided into sarcopenia risk and non-sarcopenia groups by using the Yubi–Wakka test and then further subdivided by BMI into underweight, normal weight, or obese. Oral frailty was defined as meeting three or more of six oral frailty assessment criteria adapted from previous studies. Multinomial logistic regression analysis was performed to examine the association between oral frailty and each BMI category, with normal weight used as the reference category. Results: In the sarcopenia risk group, both obesity and underweight were significantly associated with oral frailty. The odds ratio (OR) for obesity was 1.727, with a 95% confidence interval (CI) of 1.092–2.732, and the OR for underweight was 1.443, with a 95% CI of 1.066–1.952. In contrast, no significant association between BMI category and oral frailty was observed in the non-sarcopenia group. Conclusions: Among late-stage older adults at risk of sarcopenia, oral frailty was associated with both obesity and underweight, with different contributing factors identified for each BMI category.