Trends in socioeconomic inequalities in mortality from ischaemic heart disease and stroke in Australia, 1979-2006

Background: This study investigates secular trends in ischaemic heart disease (IHD) and stroke mortality by socioeconomic status (SES) in Australia to determine if absolute and relative differences between low and high SES areas have changed over time. Methods: IHD and stroke mortality data for adults aged 35-74 years and corresponding population data from Australian censuses for 1979-2006 were stratified into quintiles using an area-based measure of SES and analysed by quinquennia (and 2004-06). IHD and stroke (rates per 100,000) adjusted for age, country of birth, and rurality were compared across SES strata (separately by sex) using Poisson regression. Results: Mortality declined monotonically over the study period in all SES groups and both sexes. Absolute differences between low and high SES groups narrowed for IHD in females (27 to 23 per 100,000) and stroke in males and females (16 to 13, and 13 to 7 per 100,000, respectively), although absolute differences widened for IHD in males (52 to 63 per 100,000). Relative declines were greater in high compared to low SES groups for IHD (28% average quinquennial decline in high SES; compared with 21% in low SES for males; 30% and 21% for females), and for stroke (25% average quinquennial decline in high SES; 21% in low SES for males; 26% and 23% for females). Conclusion: Differences in mortality rates between lower and higher SES groups narrowed for both IHD (in females) and stroke (in males and females) from 1979-2006, indicating that the epidemic decline is now at a late stage when low SES groups are benefiting more, in absolute terms, than high SES groups. However males in the lower SES groups are still at an earlier stage of the epidemic decline in IHD mortality.