Lower relative income is recognized as an important social determinant of health. Poor people are also less likely to invest in oral health due to limited resources. The aims of this study was to investigate the association of preventive dental scaling with income status and change in a large population. This study was done on adults aged 30 years or older from January 2014 to December 2017 in the National Health Insurance System (NHIS) database. During this period, 558,067 individuals underwent health examinations, of whom 510,864 were adults aged 30 or older. The final sample for this study sample consisted of 497,812 adults aged 30 years and older, excluding individuals with missing data. Monthly health insurance premium data were offered in 20 quintiles, which were divided into five levels, from quintile 1 (lowest income status) to quintile 5 (highest income status). Participants’ income quintiles were aggregated annually from 2014 to 2017. The cumulative number of years with lower or higher income was used to examine the association between income changes and scaling. Multivariate analysis was used to evaluate the association of income status and health insurance type with scaling. Multiple logistic regression analysis was used to assess the association of income changes with scaling between the final observation year and the baseline year and the association between cumulative income status and the scaling. Odds ratio (ORs) and 95% confidence intervals (CIs) were estimated after adjusting for potential confounders. The ORs for the income quintile 2 and 3 groups were lower than the Medical Aid group, but overall, the lower income group was receiving less scaling (p < 0.0001). As income increased, people were more likely to perform scaling (p < 0.0001). Those receiving Medical Aid were less likely to receive scaling than those with health insurance (p < 0.0001). People with more cumulative low income status were less likely to receive scaling (p < 0.0001). Those whose base year income level improved over previous four years received more scaling and the Medical Aid and quintile 1 group required three income levels to increase ORs, while the other income groups increased ORs with a single level increase in income level (p < 0.0001). Despite insurance coverage, lower incomes were associated with less scaling and participation in scaling increased as income increased. The Medical Aid and quintile 1 groups show that, unlike other income groups, participation in scaling increases only when their income rises above a certain level. High income variability, income decline, and persistently low income were associated with lower participation in scaling.
Lee et al. (Fri,) studied this question.