Income-related inequalities in oral health over time among adults from Australia, Brazil and USA
METHODS: This study used adults nation-wide oral health survey data from Australia (n=1,200 in 1999; n=2,729 in 2005), Brazil (n=13,431 in 2003; n=9,779 in 2010), and USA (n=2,542 in 1999; n=1,596 in 2005). Dental examinations and questionnaires gathered information to define ID (<21 teeth), POH, household income, age, and sex. Absolute and relative indexes of inequalities were calculated.
RESULTS: Prevalence of ID dropped over time in Australia (from 8.7% to 3.1%), and in Brazil (42.1% to 22.4%) and was stable in the USA (~8%). Absolute income inequalities in ID were highest in Brazil, followed by the USA and Australia; relative inequalities were lower in Brazil than in Australia and the USA. Inadequate dentition was higher for the poorest group in all countries and years. A remarkable reduction in absolute inequalities were found in Australia and in Brazil while relative inequalities increased both in Australia and in Brazil. No changes in absolute and relative income inequalities were found in the USA. Perception of poor oral health reduced in Australia (4.2% to 4.8%) and in the USA (24.1% to10.7%) and increased in Brazil (24.0% to 38.3%). Perception of poor oral health was higher among poorest groups in all countries and years. Absolute over time income inequalities in POH increased in Australia and Brazil and decreased in the USA while relative inequalities increased in Australia and in the USA and decreased in Brazil.
CONCLUSIONS: Income-related inequalities in ID and POH exist and are persistent over time but improvements were found. As a reduction in absolute inequality may result in increased relative inequality both should therefore be reported and interpreted.