Public Awareness Structure of the Relationship between Self-Medication Practice and the Sustainability of Japan’s Universal Health Insurance System:

Japan’s universal health insurance system has long ensured access to high-quality medical care at relatively low cost; however, its sustainability is increasingly challenged by population aging and rising healthcare expenditures. This study examined how self-medication relates to public awareness of necessary measures for maintaining the system, perceptions of its sustainability, and recognition of threats to its continuity. A cross-sectional questionnaire survey was conducted among 314 participants at nationwide over-the-counter medicine awareness events in 2021 and 2022. Latent class analysis identified three clusters of awareness regarding system maintenance: “Efficiency-oriented with support for restrictions,” “Quality-oriented with utilization of professional support,” and “Cost-conscious with preference for service retention.” More than half of respondents (56.37％) practiced self-medication, and these individuals were significantly more likely to belong to the “Quality-oriented” cluster and to perceive the health insurance system as sustainable in the future. Self-medication practitioners also tended to focus on drug costs as a major sustainability concern, whereas nonpractitioners were more concerned about overall medical expenditure and service overuse. These findings suggest that self-medication may represent a supportive and participatory behavior that contributes to sustaining the healthcare system through responsible self-care and appropriate collaboration with professionals, rather than merely avoiding medical services.