Trends in Hospital Utilization After Medicaid Expansion

Background: Medicaid expansion was associated with an increase in hospitalizations funded by Medicaid. Whether this increase reflects an isolated payer shift or broader changes in case-mix among hospitalized adults remains uncertain. Reseearch Design: Difference-in-differences analysis of discharge data from 4 states that expanded Medicaid in 2014 (Arizona, Iowa, New Jersey, and Washington) and 3 comparison states that did not (North Carolina, Nebraska, and Wisconsin). Subjects: All nonobstetric hospitalizations among patients aged 19-64 years of age admitted between January 2012 and December 2015. Measures: Outcomes included state-level per-capita rates of insurance coverage, several markers of admission severity, and admission diagnosis. Results: We identified 6,516,576 patients admitted during the study period. Per-capita admissions remained consistent in expansion and nonexpansion states, though Medicaid-covered admissions increased in expansion states (274.6-403.8 per 100,000 people vs. 268.9-262.8 per 100,000; P < 0.001). There were no significant differences after Medicaid expansion in hospital utilization, based on per-capita rates of patients-designated emergent, admitted via the emergency department, admitted via clinic, discharged within 1 day, or with lengths of stay >= 7 days. Similarly, there were no differences in diagnosis category at admission, admission severity, comorbidity burden, or mortality associated with Medicaid expansion (P > 0.05 for all comparisons). Conclusions: Medicaid expansion was associated with a shift in payers among nonelderly hospitalized adults without significant changes in case-mix or in several markers of acuity. These findings suggest that Medicaid expansion may reduce uncompensated care without shifting admissions practices or acuity among hospitalized adults.