How much of the income inequality effect can be explained by public policy? Evidence from oral health in Brazil.

OBJECTIVES: To evaluate the association between income inequality, a public policy scale and to oral health.

METHODS: Analysis, using the Brazilian oral health survey in 2002-2003, included 23,573 15-19-year-old subjects clustered in 330 municipalities. Missing and decayed teeth and malocclusion assessments were the outcomes. Gini coefficient and a novel Scale of Municipal Public Policies were the main exposure variables. Individual level covariates were used as controls in multilevel regressions.

RESULTS: An increase from the lowest to the highest Gini value in Brazil was associated with an increase in the number of missing (rate ratio, RR=2.11 confidence interval 95% 1.18-3.77) and decayed teeth (RR=2.92 CI 95% 1.83-4.65). After adjustment for public policies and water fluoridation, the Gini effect was non-significant and public policies explained most of the variation in missing and decayed teeth. The public policy scale remained significant after adjustment with a rate ratio of 0.64 for missing and 0.72 for decayed teeth. Neither Gini nor public policies were significantly related to malocclusion. The public policy effect on missing and decayed teeth was stronger among those with higher education and income.

CONCLUSIONS: Income inequality effect was explained mainly by public policies, which had an independent effect that was greater among the better-off.