Trends in the shape of the income–mortality association in Sweden between 1995 and 2017: a repeated cross-sectional population register study

OBJECTIVE: We investigate recent trends in income inequalities in mortality and the shape of the association in Sweden. We consider all-cause, preventable and non-preventable mortality for three age groups (30–64, 65–79 and 80+ years). DESIGN AND SETTING: Repeated cross-sectional design using Swedish total population register data. PARTICIPANTS: All persons aged 30 years and older living in Sweden 1995–1996, 2005–2006 and 2016–2017 (n=8 084 620). METHODS: Rate differences and rate ratios for all-cause, preventable and non-preventable mortality were calculated per income decile and age group. RESULTS: From 1995 to 2017, relative inequalities in mortality by income increased in Sweden in the age groups 30–64 years and 65–79 years. Absolute inequalities increased in the age group 65–79 years. Among persons aged 80+ years, inequalities were small. The shape of the income–mortality association was curvilinear in the age group 30–64 years; the gradient was stronger below the fourth percentile. In the age group 65–79 years, the shape shifted from linear in 1995–1996 to a more curvilinear shape in 2016–2017. In the oldest age group (80+ years), varied shapes were observed. Inequalities were more pronounced in preventable mortality compared with non-preventable mortality. Income inequalities in preventable and non-preventable mortality increased at similar rates between 1995 and 2017. CONCLUSIONS: The continued increase of relative (ages 30–79 years) and absolute (ages 65–79 years) mortality inequalities in Sweden should be a primary concern for public health policy. The uniform increase of inequalities in preventable and non-preventable mortality suggests that a more complex explanatory model than only social causation is responsible for increased health inequalities.