Aboriginal to non-Aboriginal differentials in 2-year outcomes following non-fatal first-ever acute MI persist after adjustment for comorbidity

Abstract

Background: We investigated the relationship between Aboriginality and 2-year cardiovascular disease outcomes in non-fatal first-ever myocardial infarction during 2000-04, with progressive adjustment of covariates, including comorbidities. Design: Historical cohort study. METHODS: Person-linked hospital and mortality records were used to identify 28-day survivors of first-ever myocardial infarction in Western Australia during 2000-04 with 15-year lookback. The outcome measures were: (1) cardiovascular disease death; (2) recurrent admission for myocardial infarction; and (3) the composite of (1) and (2). Results: Compared with non-Aboriginal patients, Aboriginals were younger and more likely to live remotely. The proportions having 5-year histories of diabetes and chronic kidney disease were double and triple those of non-Aboriginals. When adjusting for demographic variables alone, the Aboriginal to non-Aboriginal hazard ratios for cardiovascular death or recurrent myocardial infarction were 3.6 (95% CI 2.5-5.3) in men and 4.5 (95% CI 2.8-7.3) in women. After adjustment for comorbidities, including diabetes, chronic kidney disease and heart failure, the hazard ratios decreased 36% and 47% to 2.3 (1.6-3.0) and 2.4 (1.5-4.0) in males and females, respectively. Conclusions: The high prevalence of comorbidities in Aboriginal people, including diabetes, kidney disease, heart failure, and other risk factors contribute substantially to the disparity in post-myocardial infarction outcomes in Aboriginal people, reinforcing the importance of both primary prevention and comprehensive management of chronic conditions in this population. Aboriginality remains a significant independent risk factor for disease recurrence or mortality, even after adjusting for comorbidity, suggesting the need for society-level interventions addressing social disadvantage.