Coevolution of education and income inequalities in mortality: is the double burden of basic education and low income becoming more lethal in Finland and Sweden over time?

BACKGROUND: Education and income are independent predictors of mortality, but they also interact so that educational inequalities in mortality are larger at low levels of income. However, the average educational attainment in high-income countries has risen during recent decades and it is unclear how these associations have changed over time. We studied these interactions in Finland and Sweden. DATA & METHODS: We used individual level register-linked data from both countries covering all individuals aged 30-64 in 3-year periods from 1994-1996 to 2018-2020. We modelled age-adjusted mortality rates (per 10 000 person-years) with three-way interactions between educational level, household income quintile and study period separately for both countries and genders using Poisson regression. RESULTS: Educational inequalities in mortality are substantially larger in lower levels of income and these inequalities are slightly larger in Finland compared with Sweden. Absolute educational inequalities in the lowest income quintile remained unchanged among men but increased substantially among women. The rate difference between basic and higher educated increased from 21 (95% CI 15 to 26) to 37 (CI 32 to 41) in Finland and from 19 (CI 14 to 24) to 31 (CI 27 to 35) in Sweden, mostly due to increasing mortality among women with basic education and low income. CONCLUSION: Due to educational expansion, the proportion of those bearing the double burden of basic education and low income is declining but they are experiencing increasing or stagnating mortality, likely driven by changes in labour market dynamics and composition of lowest educational group. Policy measures aimed at tackling health inequalities should target groups with multiple disadvantages.