Comparison of Long-term Trends in Inpatient Utilization and Costs Between Medicaid Expansion and Non-Expansion States

The Affordable Care Act’s (ACA) Medicaid Expansion significantly increased access to health insurance coverage, yet its long-term effects on hospital utilization remain understudied. This study examines the impact of Medicaid Expansion on inpatient utilization trends across early-expansion (2010-2014), late-expansion (2015-2022), and non-expansion states. Using state-level data from the Healthcare Cost and Utilization Project (HCUPnet) from 2006-2022, a state-level and aggregated interrupted time series (ITS) analysis were conducted to assess changes in inpatient discharges, length-of-stay, and hospital costs-per-stay stratified by payer type across 35 states. Findings from the state-level ITS analysis indicate that in early-expansion states, Medicaid Expansion led to an immediate but short-term shift in the payer mix with a statistically significant increase in Medicaid-covered hospital visits and a nominal decrease in uninsured visits. However, these trends were not sustained in the long term as Medicaid discharges declined and uninsured hospitalizations began to rise again. Additionally, while hospital costs-per-stay decreased among all expansion types in the short-term, these reductions were also not maintained over time. Length-of-stay for uninsured visits experienced a statistically significant decrease in the short-term but rose again in the long-term with a similar long-term trend observed for Medicaid visits. These findings suggest that while Medicaid Expansion alleviated hospital strain in the short-term, its long-term effects on utilization remain limited. The aggregated ITS analysis, based on averaged outcomes across states grouped by Medicaid Expansion status, shows a similar pattern—highlighting a statistically significant short-term increase followed by a long-term decreasing trend in Medicaid hospital discharge rates in the early expansion group compared to the late and non-expansion groups. This suggests some promising outcomes in hospital utilization for states that have expanded Medicaid. Future research should monitor and inform improvements in the implementation and sustainability of the program which should aim not only to increase access to essential health services but also to address the multifaceted social and economic drivers of health.