Temporal Trends in Acute Coronary Syndrome Incidence in Aboriginal and Non-Aboriginal People in Western Australia

Aboriginal Australians experience a disproportionate burden of acute coronary syndrome (ACS), contributing to health disparities. Evidence on changes in ACS incidence is limited. This study investigates temporal changes in the gap between Aboriginal and non-Aboriginal populations in ACS incidence and case fatality within the context of the Closing the Gap initiative, a national policy framework to reduce inequalities.

This population-based cohort study used linked hospital and mortality data for Western Australian residents aged 25 to 84 years. Incident ACS cases (2003-2020) were identified using a fixed 18-year lookback. Age-standardized incidence rates were calculated using prevalence-adjusted denominators and direct standardization. Average annual percentage changes in incidence, case fatality, and Aboriginal-to-non-Aboriginal incidence rate ratios were estimated from Poisson regression, stratified by sex and age-group (25-54, 55-84 years). Estimates were derived separately for pre-Closing the Gap (2003-2008) and post-Closing the Gap periods (2009-2016; 2017-2020).

The annual at-risk population was 1 215 300 in 2003 and 1 765 564 in 2020. We identified 4097 Aboriginal (mean age: 52.3, 40.8% women) and 64 805 non-Aboriginal (mean age: 65.1, 31.3% women) incident ACS cases. Aboriginal people had a higher prevalence of diabetes (58.5% versus 26.4%) and chronic kidney disease (27.5% versus 10.9%). ACS rates declined across all Aboriginal age/sex groups, although only significant between 2009 and 2016 for older men (-4.9%/y [95% CI, -8.9% to -0.7%]) and younger women (-4.8%/y [95% CI, -8.7% to -0.7%]). There were limited changes in incidence rate ratios between 2003 to 2008 and 2017 to 2020, respectively, in men (25-54 years, 5.2-5.6; 55-84 years, 2.9-2.1) and women (25-54 years, 10.3-10.0; 55-84 years, 2.9-3.6). Case fatality remained 20% to 50% higher among Aboriginal than non-Aboriginal people across periods and age-sex strata (risk ratios, 1.2-1.5).

Despite some evidence of declines in ACS incidence among Aboriginal groups, disparities with non-Aboriginal people persisted. Sustained Aboriginal-led efforts are needed to address underlying determinants and reduce the gap.