Association between tongue pressure, masticatory function, and salivary bacterial load in older adults requiring long-term care

Aspiration pneumonia is a major cause of mortality among older adults, with salivary bacterial load being a key contributing factor. The aim of this study was to clarify whether oral functions—including occlusal force and masticatory function—were associated with salivary bacterial counts in older individuals requiring long-term care, and to explore the relationship between tongue pressure and other oral functions to inform strategies for maintaining tongue pressure. A cross-sectional study was conducted in 80 residents (mean age: 85.4 years) of long-term care facilities in Japan. Participants underwent assessments of tongue pressure, occlusal force, masticatory ability, oral hygiene, and salivary bacterial counts. Multiple regression analysis was used to identify factors associated with increased bacterial load and decreased tongue pressure. Decreased tongue pressure was significantly associated with increased salivary bacterial counts ( P = 0.011). In turn, reduced masticatory ability was the only factor significantly associated with decreased tongue pressure ( P = 0.002). Participants with fewer than 20 teeth exhibited significantly reduced occlusal force and masticatory ability, and tended to have lower tongue pressure. Tongue pressure plays a pivotal role in controlling salivary bacterial load, and is closely linked to masticatory function. Maintaining oral functions, especially tongue pressure, may help suppress the proliferation of oral bacteria and potentially reduce the risk of aspiration pneumonia in frail older adults. Preservation of natural and functional teeth appears critical for supporting these oral functions. Longitudinal studies are warranted to evaluate whether interventions targeting oral function can reduce bacterial load and aspiration pneumonia incidence.