Early Effects of the 2014 Medicaid Expansion on Coverage and Access to Care
*Names in bold indicate Presenter
Study Design: We use restricted-access preliminary microdata from the 2014 National Health Interview Survey (NHIS) in conjunction with state geocodes for earlier years to implement a difference-in-difference research design that compares the evolution of regression-adjusted outcomes between expansion and opt-out states. In addition to estimating the impact of state expansion status on these outcomes, we estimate instrumental variables models that identify impacts on access to care, patterns of care-seeking, health status, and mental health for the average childless adult gaining insurance coverage due to the expansion.
Population Studied: We are studying childless adults in families with income below 100 percent of the federal poverty level. We will compare coverage, utilization, and health outcomes for low-income adults gaining coverage under the expansion to outcomes for similarly situated adults in opt-out states.
Principal Findings: We anticipate that the regression-adjusted outcomes being examined will differ between opt-in and opt-out states. Our research design will allow us to identify the causal effect of Medicaid eligibility on insurance status, showing the extent to which the Medicaid expansion has led to coverage gains after alternative sources of coverage are taken into account. We will also be able to measure whether Medicaid coverage makes low-income adults more likely to have a usual place of care; whether that usual place of care is more likely to be a doctor's office rather than an emergency department or clinic; and whether low-income adults are less likely to report delaying or foregoing needed care due to costs. Finally, we will estimate the short-run causal effects of insurance coverage on mental health and self-reported health status.
Conclusions: While state decisions to decline the Medicaid expansion may reduce access to insurance, differences in the ACA's implementation between opt-out and expansion states create a valuable opportunity for rigorous evaluation of the effects of Medicaid expansion on coverage, utilization, and outcomes. This study represents the first household-level evaluation of the effects of state Medicaid expansion decisions on these variables. Our basic research design uses a difference-in-difference framework to distinguish changes in regression-adjusted outcomes associated with the Medicaid expansion from permanent differences between states and from nationwide changes associated with ACA implementation.
Implications for Health Policy: This research will help policymakers in opt-out states understand the population health costs of continuing to decline the Medicaid expansion. Meanwhile, our research will help policymakers in opt-in states identify possible shortcomings in the Medicaid expansion's implementation and set health policy priorities accordingly.