Unwinding of Medicaid enrollment and increased uninsured emergency department visits in California

Objective To examine the association between post–pandemic era Medicaid eligibility redeterminations (“unwinding”) and emergency department (ED) payer mix in California. Methods We conducted a retrospective secondary analysis of California's quarterly ED visit data (2021–2024) across 281 general acute-care hospitals, using interrupted time-series analysis. Results During unwinding, Medicaid ED visits declined by 0.37 percentage points (pp) and uninsured ED visits increased by 0.16 pp per quarter (P <.001) relative to the pre-unwinding period. The largest Medicaid declines occurred in investor-owned (0.87 pp, 11.9%) and medium-sized (0.47 pp, 7.4%) hospitals (P <.001). In contrast, the largest increases in uninsured visits occurred among hospitals in rural (0.29 pp, 46.7%) and high-poverty (0.24 pp, 7.7%) areas, in addition to small hospitals (0.22 pp, 25.8%) (P <.001). Private visits saw an immediate decrease of 0.49 pp (P <.001), followed by a continued reduction of 0.15 pp per quarter (P <.05), showing flattening of the previously increasing trend. Medicare visits increased by 0.18 pp per quarter (P <.001) relative to the pre-unwinding period. Conclusion Medicaid unwinding was associated with a decline in Medicaid ED visits and a corresponding increase in uninsured ED visits, with varying impacts across hospital types in California.