Medicaid Expansion and Medicare-Financed Hospitalizations Among Adult Patients With Incident Kidney Failure.

Importance: Although Medicare provides health insurance coverage for most patients with kidney failure in the US, Medicare beneficiaries who initiate dialysis without supplemental coverage are exposed to substantial out-of-pocket costs. The availability of expanded Medicaid coverage under the Patient Protection and Affordable Care Act (ACA) for adults with kidney failure may improve access to care and reduce Medicare-financed hospitalizations after dialysis initiation. Objective: To examine the implications of the ACA's Medicaid expansion for Medicare-financed hospitalizations, health insurance coverage, and predialysis nephrology care among Medicare-covered adults aged 19 to 64 years with incident kidney failure in the first year after initiating dialysis. Design, Setting, and Participants: This cross-sectional study used a difference-in-differences approach to assess Medicare-financed hospitalizations among adults aged 19 to 64 years who initiated dialysis between January 1, 2010, and December 31, 2018, while covered by Medicare Part A (up to 5 years postexpansion). Data on patients were obtained from the Renal Management Information System's End Stage Renal Disease Medical Evidence Report, which includes data for all patients initiating outpatient maintenance dialysis regardless of health insurance coverage, treatment modality, or citizenship status, and these data were linked with claims data from the Medicare Provider Analysis and Review. Data were analyzed from January to August 2022. Exposure: Living in a Medicaid expansion state. Main Outcomes and Measures: Primary outcomes were number of Medicare-financed hospitalizations and hospital days in the first 3 months, 6 months, and 12 months after dialysis initiation. Secondary outcomes included dual Medicare and Medicaid coverage at 91 days after dialysis initiation and the presence of an arteriovenous fistula or graft at dialysis initiation for patients undergoing hemodialysis. Results: The study population included 188 671 adults, with 97 071 living in Medicaid expansion states (mean [SD] age, 53.4 [9.4] years; 58 329 men [60.1%]) and 91 600 living in nonexpansion states (mean [SD] age, 53.0 [9.6] years; 52 677 men [57.5%]). In the first 3 months after dialysis initiation, Medicaid expansion was associated with a significant decrease in Medicare-financed hospitalizations (-4.24 [95% CI, -6.70 to -1.78] admissions per 100 patient-years; P = .001) and hospital days (-0.73 [95% CI, -1.08 to -0.39] days per patient-year; P < .001), relative reductions of 8% for both outcomes. Medicaid expansion was associated with a 2.58-percentage point (95% CI, 0.88-4.28 percentage points; P = .004) increase in dual Medicare and Medicaid coverage at 91 days after dialysis initiation and a 1.65-percentage point (95% CI, 0.31-3.00 percentage points; P = .02) increase in arteriovenous fistula or graft at initiation. Conclusions and Relevance: In this cross-sectional study with a difference-in-differences analysis, the ACA's Medicaid expansion was associated with decreases in Medicare-financed hospitalizations and hospital days and increases in dual Medicare and Medicaid coverage. These findings suggest favorable spillover outcomes of Medicaid expansion to Medicare-financed care, which is the primary payer for patients with kidney failure.