Association between vehicle ownership and disparities in mortality after myocardial infarction

Access to reliable transportation is fundamental in the management of chronic disease. The purpose of this study was to investigate the association between vehicle ownership at the neighborhood-level and long-term mortality after myocardial infarction (MI).

This is a retrospective observational study evaluating adult patients admitted for MI between January 1st, 2006, and December 31st, 2016. Neighborhoods were defined by census tract and household vehicle ownership data was obtained from the American Community Survey courtesy of the University of California, Los Angeles Center for Neighborhood Knowledge. Patients were divided into 2 groups: those living in neighborhoods with higher vehicle ownership, and those living in neighborhoods with lower vehicle ownership. The cutoff of 4.34% of households reporting not owning a vehicle was used to define a neighborhood as one with "higher" vs "lower" vehicle ownership as this was the median value for the cohort. The association between vehicle ownership and all-cause mortality after MI was assessed using Cox proportional hazards regression models.

A total of 30,126 patients were included (age 68.1 +/- 13.5 years, 63.2% male). After adjusting for age, sex, race/ethnicity, and medical comorbidities, lower vehicle ownership was associated with increased all-cause mortality after MI (hazard ratio [HR] 1.10; 95% confidence interval [CI] 1.06-1.14; p<0.001). This finding remained significant after adjusting for median household income (HR 1.06; 95% CI 1.02-1.10; p = 0.007). Upon comparison of White and Black patients living in neighborhoods with lower vehicle ownership; Black patients were found to have an increased all-cause mortality after MI (HR 1.21, 95% CI 1.13-1.30, p<0.001), a difference which remained significant after adjusting for income (HR 1.20; 95% CI 1.12-1.29; p<0.001). There was no significant difference in mortality between White and Black patients living in neighborhoods with higher vehicle ownership.

Lower vehicle ownership was associated with increased mortality after MI. Black patients living in neighborhoods with lower vehicle ownership had a higher mortality after MI than White patients living in similar neighborhoods but Black patients living in neighborhoods with higher vehicle ownership had no worse mortality than their White counterparts. This study highlights the importance of transportation in determining health status after MI.