Socioeconomic Inequalities in Oral Frailty Among Older Adults: A Causal Mediation Analysis on the Role of Prevention From Tooth Loss

Background Although social inequalities in oral health have been suggested, the link between socioeconomic status (SES) and oral frailty (OF) remains unclear. We aimed to investigate the inequalities in OF according to SES and the extent to which inequalities are mitigated by preventing tooth loss. Methods We used cross‐sectional data from 21 542 functionally independent participants aged ≥ 65 (48.5% men) from the Japan Gerontological Evaluation Study. The prevalence of OF, number of teeth, and educational attainment (EA) and equivalent income (EI) were used as outcome, mediator and explanatory variables, respectively. A Poisson regression model was used to examine the association between SES and OF. Causal mediation analysis was performed to calculate the prevalence ratios (PRs) and 95% confidence intervals (CIs) of the controlled direct effects (CDEs) of the number of teeth. The proportion eliminated (PE) of the ≥ 20 remaining teeth was calculated. Results Overall 7984 participants had OF. The prevalence of OF was 1.45 times higher in participants with ≤ 9 years of EA and 1.38 times higher in participants with an EI of < $20.000. The estimated total effect (TE) of low EA or low EI on the prevalence of OF was mediated by the number of teeth (TE PR, 1.30 [95% CI, 1.25–1.35]; CDE PR, 1.22 [95% CI, 1.10–1.33]; PE, 28.2%) or (TE PR, 1.26 [95% CI, 1.22–1.31]; CDE PR, 1.23 [95% CI, 1.14–1.32]; PE, 12.9%). Conclusion OF showed a clear social gradient based on SES. However, this association could be mediated by the remaining ≥ 20 teeth.