Association of Medicaid Expansion With Cardiovascular Mortality.

Importance: Medicaid expansion under the Patient Protection and Affordable Care Act led to one of the largest gains in health insurance coverage for nonelderly adults in the United States. However, its association with cardiovascular mortality is unclear. Objective: To investigate the association of Medicaid expansion with cardiovascular mortality rates in middle-aged adults. Design, Setting, and Participants: This study used a longitudinal, observational design, using a difference-in-differences approach with county-level data from counties in 48 states (excluding Massachusetts and Wisconsin) and Washington, DC, from 2010 to 2016. Adults aged 45 to 64 years were included. Data were analyzed from November 2018 to January 2019. Exposures: Residence in a Medicaid expansion state. Main Outcomes and Measures: Difference-in-differences of annual, age-adjusted cardiovascular mortality rates from before Medicaid expansion to after expansion. Results: As of 2016, 29 states and Washington, DC, had expanded Medicaid eligibility, while 19 states had not. Compared with counties in Medicaid nonexpansion states, counties in expansion states had a greater decrease in the percentage of uninsured residents at all income levels (mean [SD], 7.3% [3.2%] vs 5.6% [2.7%]; P < .001) and in low income strata (19.8% [5.5%] vs 13.5% [3.9%]; P < .001) between 2010 and 2016. Counties in expansion states had a smaller change in cardiovascular mortality rates after expansion (146.5 [95% CI, 132.4-160.7] to 146.4 [95% CI, 131.9-161.0] deaths per 100 000 residents per year) than counties in nonexpansion states did (176.3 [95% CI, 154.2-198.5] to 180.9 [95% CI, 158.0-203.8] deaths per 100 000 residents per year). After accounting for demographic, clinical, and economic differences, counties in expansion states had 4.3 (95% CI, 1.8-6.9) fewer deaths per 100 000 residents per year from cardiovascular causes after Medicaid expansion than if they had followed the same trends as counties in nonexpansion states. Conclusions and Relevance: Counties in states that expanded Medicaid had a significantly smaller increase in cardiovascular mortality rates among middle-aged adults after expansion compared with counties in states that did not expand Medicaid. These findings suggest that recent Medicaid expansion was associated with lower cardiovascular mortality in middle-aged adults and may be of consideration as further expansion of Medicaid is debated.