Importance
Over the last decade, acute myocardial infarction (AMI) incidence and mortality have decreased substantially. Yet it is unknown whether these improvements were consistent across communities of different economic status and geographic regions, for which efforts to improve cardiovascular disease prevention and management may have had variable impact.
Objective
To determine whether trends in county-level risk-standardized AMI hospitalization and mortality rates varied by county-based median income level.
Design
Observational study from 1999 to 2013.
Setting
National study of U.S. counties.
Participants
County-level risk-standardized (age, sex, race) hospitalization and 1-year mortality rates for AMI from 1999 to 2013 were measured for Medicare beneficiaries ≥65 years.
Exposures
Counties were stratified by median income percentile using 1999 U.S. Census Bureau data, adjusted for inflation: low (<25th), average (25–75th) or high (>75th) income groups.
Main Outcome and Measure
We examined the effect of income on the slope of AMI hospitalizations and mortality. We measured differences in rate of change in AMI hospitalizations and mortality by county income and by the 4 U.S. geographic regions. We also tested for a ‘lag’ effect among low-income counties.
Results
In the 15-year period, AMI risk-standardized hospitalization and mortality rates decreased significantly for all three county income groups. Average hospitalization rates were significantly higher among low-income counties compared with high-income counties, with rates for low-income counties in 2013 lower than for high-income counties in 1999 (853 versus 1,123 per 100,000 person years, respectively). 1-year mortality rates after hospitalization for AMI were similar across county income groups, decreasing from 1999 (31.5%, 31.4%, and 31.1%, for high, average and low income counties, respectively) to 2013 (26.2%, 26.1%, and 25.4%). The rate of decline in AMI hospitalizations was similar for all county income groups; however, low-income counties lagged behind high-income counties by 4.3 (95% CI 3.1 to 5.9) years. There were no differences in trends across geographic regions.
Conclusion and Relevance
AMI hospitalization and mortality rates declined among counties of all income levels, though hospitalization rates among low-income counties lag behind. These findings lend support for a more targeted community-based approached to AMI prevention.