Income or education, which has a stronger association with dental implant use in elderly people in Japan?

Objectives: Although inequalities in dental implant use based on educational level have been reported, no study has used income as a proxy for the socioeconomic status. We examined: (i) income inequalities in implant use; and (ii) whether income or education has a stronger association with implant use in elder Japanese. Methods: In 2016, a self-reported questionnaire was mailed to participants aged 65 years or older living across Japan as part of the ongoing Japan Gerontological Evaluation Study. We used data from 84,718 respondents having 19 or fewer teeth. After multiple imputation, multi-level logistic regression estimated the association of dental implant use with equivalised income level and years of formal education. Confounders were age, sex, and density of dental clinics in the residential area. Results: 3.1% of respondents had dental implants. Percentages of dental implant use among the lowest (≤ 9 years) and highest (≥ 13 years) educational groups were 1.8 and 5.1, respectively, and among the lowest (0 < 12.2 ‘1,000 USD/year’) and highest (≥ 59.4 ‘1,000 USD/year’) income groups were 1.7 and 10.4, respectively. A fully adjusted model revealed that both income and education were independently associated with dental implant use. Odds ratios for implant use in the highest education and income groups were 2.13 [95% CI = 1.94–2.35] and 4.85 [95% CI = 3.78–6.22] compared with the lowest education and income groups, respectively. From a model with standardised variables, income showed slightly stronger association than education. Conclusion: This study reveals a public health problem that even those with the highest education but low income might have limited accessibility to dental implant services.