Objectives: Socioeconomic disparities in oral health have been widely reported worldwide, yet evidence among adults in Japan remains limited. This study aimed to examine the associations between socioeconomic status (SES) and both dental diseases and oral health-related behaviors in a nationally representative sample of Japanese adults. Methods: We analyzed data from 28,617 participants in the 2022 Japan “COVID-19 and Society” Internet Survey (JACSIS), a nationwide, cross-sectional, web-based questionnaire. The exposure variable was equivalent household income, categorized into quintiles. Outcomes included self-reported periodontal disease, dental caries, and four dental behaviors: Daily tooth brushing, daily snacking, annual preventive dental visits, and annual treatment dental visits. Logistic regression analyses were conducted using inverse probability weighting (IPW) to adjust for potential selection bias, adjusting for demographic, socioeconomic, health-related, and regional covariates. Results: Lower equivalent household income was significantly associated with higher odds of dental disease and lower engagement in preventive or treatment-related dental visits. Participants in the lowest income quintile were more likely to report periodontal disease (adjusted odds ratios AOR, 1.32; 95% confidence interval ( CI ), 1.06–1.65) or dental caries (AOR, 1.63; 95% CI , 1.29–2.05) and less likely to undergo annual preventive dental visits (AOR, 0.59; 95% CI , 0.51–0.69) compared with those in the highest quintile. A dose–response relationship was observed for some outcomes. Conclusion: Clear socioeconomic disparities exist in both dental diseases and preventive behaviors among adults in Japan. Policies promoting preventive dental visits and reducing income-related inequalities are essential to achieving equitable oral health and mitigating broader health disparities.
Ito et al. (2026) studied this question.