Affordable Care Act State-Specific Medicaid Expansion: Impact on Health Insurance Coverage and Breast Cancer Screening Rates

Background: Under the Affordable Care Act, states were given the option to expand Medicaid in 2014. By the end of 2014, 32 states had opted to expand Medicaid while 19 did not. Previous quasi-experimental studies took advantage of this state-specific policy implementation and found increased insurance coverage in expansion compared to non-expansion states. With longer-term data now available, we studied the effect of Medicaid expansion on changes in insurance coverage and mammography rates in expansion and non-expansion states.

Study Design: Seven states which expanded Medicaid eligibility in 2014 and six non-expansion states were selected based on available data. The U.S. Census American Community Survey was queried for insurance coverage from 2011-2016 and the Centers for Disease Control and Prevention Behavioral Risk Factor Surveillance System from 2010-2018. Difference-in-difference linear mixed models were used to estimate and compare insurance coverage and screening mammogram rates between expansion and non-expansion states before and after 2014.

Results: The increase in insurance rates for all persons covered by some type of health insurance after Medicaid expansion was significantly different in expansion than non-expansion states (p=0.001). The increase in Medicaid coverage was significant in expansion compared to non-expansion states (p<0.001). A similar trend was seen in screening mammogram rates in women from low income households in expansion versus non-expansion states (p=0.049).

Conclusion: Medicaid expansion states saw greater improvement in total insurance and Medicaid coverage, and in mammogram rates in lower income women, when compared to non-expansion states after Medicaid legislation was passed. Our study demonstrates that people do take advantage of expanded eligibility by acquiring insurance and this may improve access to preventive measures such as screening mammography.