Rural-urban difference in acute myocardial infarction mortality: Evidence from Nebraska

Background: Acute myocardial infarction (AMI) remains a major cause of death and disability in the United States and worldwide. Despite the importance of surveillance and secondary prevention, the incidence of and mortality from MI are not continuously monitored, and little is known about survival outcomes after 30 days of MI hospitalization or associated risk factors, especially in the rural areas. The current study examines rural-urban differences in both in-and out-hospital survival outcomes for AMI patients.

Methods: We performed a retrospective analysis using 5 years of hospital discharge data in Nebraska from January 2005 to December 2009 and Nebraska death certificate records through October 2011. Both datasets were linked by a probabilistic linkage technique using patient name, date of birth, sex, and residence ZIP code. Multivariate logistic regression was used to estimate the rural-urban difference in 30-day mortality. A Cox proportional hazard model was used to predict overall survival rate. The control variables in the study included patient age, sex, and comorbidities.

Results: From 2005 to 2009, 12,783 patients were hospitalized for AMI in Nebraska. In the 30-day mortality model, after controlling for age, comorbidities, and rehabilitation, patients in rural areas were 37% more likely to die than patients from urban areas. In the overall survival model, patients in urban areas had a lower hazard of AMI death (HR: 0.85, p <.0001) than patients in rural areas. Patients with previous history of heart failure had a significantly higher likelihood of 30-day mortality, while atrial fibrillation, heart failure, and chronic kidney disease were associated with higher overall mortality. Patients who attended at least one previous cardiac rehabilitation session had significantly lower 30-day and overall mortality (p <.0001).

Conclusions: The results from this study not only support previous findings on rural-urban disparity in 30-day mortality, but also extend them to after 30 days of AMI hospitalization. Cardiac rehabilitation is also associated with reduced mortality, a finding which has never been reported at the population level. Further efforts are needed to develop systems in rural hospitals and communities to ensure that AMI patients receive recommended care.