## 4 Discussion  
The weakening of the tongue and buccinator muscle, among other orofacial muscles, has been recognized as a risk factor for the development of swallowing difficulties [14,19]. A scoping review highlighted that tongue strength is an important predictor of cognitive decline in dementia, which has often been overlooked in previous studies [44]. Since the primary risk factors for reduced orofacial muscle strength include diseases that negatively impact the sensorimotor system, previous studies have largely focused on long-term hospitalized older adults with cerebrovascular diseases or neurogenic disorders [19,23,24]. Limited research exists on the influence of oral health conditions, a modifiable factor, on maintaining orofacial muscle strength in healthy older adults living independently. Given the high prevalence of dysphagia even among older adults without causal conditions such as stroke [18], the functional status of orofacial muscles that are directly related to swallowing abilities, as well as the risk factors contributing to their weakening, must be considered in healthy older adults. This study, therefore, assessed the anterior tongue elevation, cheek compression, and lip compression strengths in 70 healthy older adults aged 65 years or older, living independently in the community without diseases contributing to dysphagia, and analyzed the potential factors related to each muscle strength, particularly oral health status. The final regression models used to elucidate the intensity of the associations with orofacial muscle strength demonstrated that the orofacial muscle strength was associated with several oral health-related factors. However, significant factors differed between tongue elevation strength, cheek compression strength, and lip compression strength. A reduced tongue elevation strength was most strongly associated with older age, followed by having 0-9 remaining teeth and discomfort in pronunciation due to oral problems. A reduced cheek compression strength was most strongly associated with older age, a smaller number of remaining teeth, and discomfort in mastication due to oral problems. A weakened lip compression strength was most significantly associated with poor self-rated oral health, followed by diabetes, female sex, and a low unstimulated salivary flow rate. We did not find any common factors associated with all three orofacial muscle strengths except for age, number of remaining teeth, and discomfort due to oral problems for tongue elevation strength and cheek compression strength. We speculated that the associated factors differed because each muscle plays a different role. However, this study was not able to identify the exact cause. The role of each orofacial muscle has been investigated in previous studies. Among the orofacial muscles, the buccinator, also known as the accessory mastication muscle, is a square-shaped major facial muscle located in the cheek area between the maxilla and mandible, which maintains the position of the food bolus in the mouth by compressing the cheeks against the teeth during chewing to help mastication [45,46]. The strength of the buccinator muscle has been considered a valuable indicator for diagnosing orofacial weakness [14]. The tongue is a complex muscle primarily responsible for manipulating food and pushing it from the oral cavity toward the pharynx [11]. Additionally, the orbicularis, the principal muscle of the lips, is crucial for creating a lip seal to prevent the food bolus from leaking out of the oral cavity during chewing [45]. Therefore, considering the specific role played by each muscle, it is necessary to confirm the results of this study in future studies with a larger sample size. In this study, the main potential factors associated with orofacial muscle strength were as follows. First, older age was the most significant factor associated with both tongue and cheek muscle weakness (\(p<0.05\)).