Oral Health Mediates Income Decline Over Time in Australian Adults

The objective of this study was to investigate if poor oral health mediates income losses over a 12-y follow-up period in Australian adults. Data were obtained from adults aged ≤65 y, selected to minimize the influence of retirement, who participated in both waves (2004-2006 and 2017-2018) of the National Study of Adult Oral Health (NSAOH), nationally representative surveys of Australians aged ≥15 y. Baseline household income, categorized as low ($80,000), was the exposure, and follow-up household income was the outcome, which was inflation-adjusted using the Consumer Price Index (CPI) to ensure comparability across both waves and account for changes in purchasing power over time. Change in self-reported oral health, categorized as "good" (excellent/very good/good at both waves) or "poor" (persistently poor or declined to poor), was examined as a mediator. Marginal structural models using multinomial logistic regression and inverse probability weighting estimated indirect (mediated) effects of poor oral health on income loss, adjusting for sociodemographic and behavioral confounders. Missing data were handled using multiple imputation, and E-values assessed robustness to unmeasured confounding. A total of 707 adults were included (mean [SD] age at baseline: 41.4 [8.17] y; males: 40.6%). At baseline, 19.6%, 46.7%, and 33.7% reported low, medium, and high income, respectively, and 15% reported poor oral health. Compared to high baseline income, individuals with medium income had a 3.10 times higher risk of shifting to low income (vs. high income) at follow-up, with poor oral health mediating 5% to 7% of this effect. The population-attributable fraction for the mediated effect was 2.1%, equivalent to approximately 376,932 Australian adults whose income decline may be partly explained by deteriorating oral health. Poor oral health partially mediated long-term income decline among Australian adults, underscoring the sustained economic burden of oral health inequalities.