Incidence and survival after acute myocardial infarction in Indigenous and non-Indigenous people in the Northern Territory, 1992-2004

Objective: To estimate the incidence and survival rates of acute myocardial infarction (AMI) for Northern Territory Indigenous and non-Indigenous populations. Design and participants: Retrospective cohort study for all new AMI cases recorded in hospital inpatient data or registered as an ischaemic heart disease (IHD) death between 1992 and 2004. Main outcome measures: Population-based incidence and survival rates by age, sex, Indigenous status, remoteness of residence and year of diagnosis. Results: Over the 13-year study period, the incidence of AMI increased 60% in the NT Indigenous population (incidence rate ratio (IRR), 1.04; 95% CI, 1.02-1.06), but decreased 20% in the non-Indigenous population (IRR, 0.98; 95% CI, 0.97-1.00). Over the same period, there was an improvement in all-cases survival (ie, survival with and without hospital admission) for the NT Indigenous population due to a reduction in deaths both pre-hospital and after hospital admission (death rates reduced by 56% and 50%, respectively). The non-Indigenous all-cases death rate was reduced by 29% as a consequence of improved survival after hospital admission; there was no significant change in pre-hospital survival in this population. Important factors that affected outcome in all people after AMI were sex (better survival for women), age (survival declined with increasing age), remoteness (worse outcomes for non-Indigenous residents of remote areas), year of diagnosis and Indigenous status (hazard ratio, 1.44; 95% CI, 1.21-1.70). Conclusions: Our results show that the increasing IHD mortality in the NT Indigenous population is a consequence of a rise in AMI incidence, while at the same time there has been some improvement in Indigenous AMI survival rates. The simultaneous decrease in IHD mortality in NT non-Indigenous people was a result of reduced AMI incidence and improved survival after AMI in those admitted to hospital. Our results inform population-specific strategies for a systemwide response to AMI management.