Soft-Tissue Facial Profile Is Associated With Tongue Pressure in Adults: A Cross-Sectional Study

Objective Oral frailty, including reduced tongue pressure, has been increasingly recognized as a risk factor for systemic frailty in older adults. Although the relationship between skeletal and perioral muscle function and maxillofacial morphology has attracted growing attention in orthodontics, it is insufficiently understood. This study aimed to investigate the associations between sagittal and vertical soft-tissue facial profile and tongue pressure and skeletal muscle mass in adults. Materials and methods This cross-sectional study included 75 participants (median age: 69 years; 67% women) from the Kanagawa Dental University Hospital. Lateral facial photographs were used to measure the soft-tissue nasion-subnasale-soft-tissue pogonion (N'-Sn-Pog') angle (sagittal morphology) and soft-tissue nasion-tragion-soft-tissue menton (N'-Tra-Me') angle (vertical morphology). Tongue pressure was assessed using a balloon-type device, and skeletal muscle mass was measured via body composition analysis. Spearman's correlation and multiple regression analyses, adjusted for age, sex, and height, were performed. Results Tongue pressure showed a significant positive correlation with the N'-Sn-Pog' angle and no correlation with the N'-Tra-Me' angle. Multiple regression indicated an independent association between tongue pressure and the N'-Sn-Pog' angle. A positive association between skeletal muscle mass and the N'-Sn-Pog' angle was found in a model excluding sex as a variable. Conclusion In middle-aged and older adults, sagittal soft-tissue facial morphology, as indicated by the N'-Sn-Pog' angle, was positively associated with tongue pressure. These findings suggest that a simple and non-invasive assessment based on facial photographs may serve as a potential indicator of reduced tongue pressure.