The Affordable Care Act was signed into law in 2010, expanding Medicaid and improving access to care for millions of low-income Americans. Fewer uninsured individuals reduced the cost of uncompensated care, consequently improving the financial health of hospitals. We hypothesize that this amelioration in hospital finances resulted in a marked improvement of quality measures in states that chose to expand Medicaid. To our knowledge, the impact of Medicaid expansion on the Medicare population has not been investigated. Using a difference-in-difference analysis, we compare readmission rates for four measures from the Hospital Readmission Reduction Program: acute myocardial infarction, pneumonia, heart failure, and coronary artery bypass graft surgery. Our analysis provides evidence that between 2013 and 2021 expansion states improved hospital quality relative to non-expansion states as it relates to acute myocardial infarction readmissions (p = 0.015) and coronary artery bypass graft surgery readmissions (p = 0.039). Our analysis provides some evidence that expanding Medicaid improved hospital quality, as measured by a reduction in readmission rates. Using visualizations, we provide some evidence that hospital quality improved for the other two measures as well. We believe that a refinement of our estimation method and an improved dataset will increase our chances of finding significant results for these two other measures.

翻译：《平价医疗法案》于2010年签署成为法律，该法案扩展了医疗补助计划并改善了数百万低收入美国人的医疗可及性。未参保人数的减少降低了无偿医疗的成本，从而改善了医院的财务状况。我们假设，这种医院财务状况的改善导致选择扩展医疗补助计划的州在质量指标上出现显著提升。据我们所知，医疗补助计划扩展对医疗保险参保人群的影响尚未得到研究。通过双重差分分析，我们比较了医院再入院减少计划中四项指标的再入院率：急性心肌梗死、肺炎、心力衰竭和冠状动脉旁路移植手术。我们的分析证明，在2013年至2021年间，扩展州在医院质量方面相对于非扩展州有所提升，具体体现在急性心肌梗死再入院率（p = 0.015）和冠状动脉旁路移植手术再入院率（p = 0.039）的改善。我们的分析提供了一定证据，表明扩展医疗补助计划通过降低再入院率来衡量，改善了医院质量。通过可视化分析，我们还为另外两项指标的医院质量提升提供了一些证据。我们相信，通过改进估计方法和完善数据集，将增加我们在另外两项指标上发现显著结果的可能性。