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

ABSTRACT

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.