Ninjin’yoeito for Impaired Oral Function in Older Adults: A Prospective, Open-Label Pilot Study

<i>Background and Objectives:</i> Japan's aging population faces growing challenges related to oral frailty, a condition characterized by the decline of oral function associated with physical and nutritional deterioration. Impaired oral function contributes to reduced chewing, swallowing, and saliva secretion, leading to poor appetite and frailty progression. Ninjin'yoeito (NYT), a traditional Kampo formula, has been clinically used to improve systemic weakness and oral symptoms. This study aimed to evaluate the efficacy and safety of NYT in improving oral health among elderly individuals with impaired oral function. <i>Materials and Methods:</i> In this open-label prospective study, patients received NYT daily for 12 weeks. Assessments included oral symptom scores, mucosal moisture, repetitive saliva swallowing tests (RSST), gustatory function by visual analogue scale (VAS), an 11-item oral questionnaire, and immune profiling by flow cytometry. Safety was assessed through hematological and biochemical tests. <i>Results</i>: Symptom scores decreased from 8.27 at baseline to 3.64 at 12 weeks (<i>p</i> = 0.006), while oral condition scores improved from 5.09 to 1.36 (<i>p</i> = 0.006). Mucosal moisture increased (25.1 to 28.1, <i>p</i> = 0.03), and RSST frequency improved (2.18 to 4.55, <i>p</i> = 0.046). Questionnaire scores declined from 5.1 to 2.0 (<i>p</i> < 0.001). VAS-taste was unchanged overall (<i>p</i> = 0.21) but improved in low baseline patients. Laboratory findings showed no adverse changes, with favorable lipid trends. Immune analysis revealed a decline in NKG2D expression (<i>p</i> = 0.02), whereas other activating and inhibitory markers remained stable. <i>Conclusions</i>: NYT was well tolerated and associated with gradual improvements in oral and physical symptoms among elderly individuals with impaired oral function. These findings provide preliminary evidence supporting the feasibility of Kampo-based approaches for maintaining oral health in aging populations and warrant further validation in larger controlled trials.