Village Forest Experience Program Improves Cognitive Function and Reduces Salivary Cortisol and Oral Pathogens in Older Adults

Background/Objectives: Forest therapy has demonstrated stress-reducing and immune-enhancing effects, yet its simultaneous impact on cognitive function, stress biomarkers, and oral microbiota in older adults remains unexplored. This study aimed to evaluate the effects of an 8-week community-based village forest experience program on cognitive function, salivary cortisol, and oral pathogenic bacteria in community-dwelling older adults. Methods: A total of 125 older adults (mean age 82.2 ± 5.3 years; 87.2% female) from 17 senior centers participated in a single-arm, pre–post intervention study. Cognitive function was assessed using the Cognitive Impairment Screening Test (CIST), salivary cortisol was measured by ELISA, and seven oral bacterial species were quantified by qPCR. Results: CIST scores improved significantly (p = 0.003, d = 0.27), with the suspected cognitive impairment subgroup showing greater improvement (d = 0.66) and 48.8% transitioning to normal classification. Salivary cortisol decreased significantly (p = 0.002), and total bacterial load, Porphyromonas gingivalis, and Tannerella forsythia were significantly reduced. The 80–84-year age group showed the greatest cognitive gain, whereas participants aged 85 and older showed no significant change. Conclusions: An accessible village forest program may simultaneously benefit cognitive function, stress, and oral health in older adults with early-stage cognitive decline. Controlled studies are needed to confirm causality and elucidate the underlying mechanisms.