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

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 and 19 did not. Previous quasi-experimental studies took advantage of this state-specific policy implementation and found increased insurance coverage in expansion compared with nonexpansion 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 nonexpansion states.

Study Design: Seven states that expanded Medicaid eligibility in 2014 and 6 nonexpansion states were selected based on available data. The US Census American Community Survey was queried for insurance coverage from 2011 to 2016 and the CDC Behavioral Risk Factor Surveillance System from 2010 to 2018. Difference-in-difference linear mixed models were used to estimate and compare insurance coverage and screening mammogram rates between expansion and nonexpansion 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 nonexpansion states (p = 0.001). The increase in Medicaid coverage was significant in expansion compared with nonexpansion states (p < 0.001). A similar trend was seen in screening mammogram rates in women from low-income households in expansion vs nonexpansion states (p = 0.049).

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