Abstract
BACKGROUND: Oral hypofunction (OHF) is a multidimensional condition representing a subclinical decline in oral function. Cross-national comparisons using standardised criteria remain limited. OBJECTIVES: This study aimed to compare the prevalence and characteristics of OHF among community-dwelling adults in Japan and Switzerland and to examine age-related patterns using standardised assessments. METHODS: A cross-sectional study was conducted in community settings in Japan (153 participants) and in a university dental clinic in Switzerland (117 participants). OHF assessments were performed between May 2023 and January 2024 in Japan and between December 2023 and January 2024 in Switzerland. Data were collected by trained and calibrated examiners from both countries following standardised protocols. OHF was diagnosed when three or more of the seven oral function domains, including oral hygiene, oral dryness, occlusal force, tongue-lip motor function, tongue pressure, masticatory function, and swallowing function, were impaired. Multiple logistic regression analyses were performed with OHF as the outcome after adjusting for country, age, and covariates. Interactions between country and age were also investigated. RESULTS: The prevalence of OHF was 30.7% in Japanese participants and 49.6% in Swiss participants (p = 0.002). The Swiss participants demonstrated significantly better oral hygiene (p < 0.001), while the Japanese participants showed better tongue pressure (p = 0.026), lip-tongue motor function (p < 0.001), maximum occlusal force (p = 0.002), and masticatory function (p < 0.001). In logistic regression, OHF was associated with Swiss nationality (odds ratio [OR]: 3.85, 95% confidence interval [CI]: 1.85-8.00, p < 0.001), age ≥ 70 years (OR: 5.73, 95% CI: 1.67-19.68, p = 0.006, compared to those in their 20s), lower hand grip strength (OR: 0.91, 95% CI: 0.87-0.96, p = 0.001), and fewer teeth (OR: 0.94, 95% CI: 0.89-0.98, p = 0.008). A significant interaction between country and age indicated differing age-related OHF progression between the Japanese and Swiss populations. CONCLUSION: Both populations exhibited age-related declines in oral function; however, functional impairment was more prevalent and progressive in Switzerland. These findings support the cross-cultural applicability of the OHF criteria and underscore the need for population-specific preventive strategies.