Association for Public Policy Analysis & Management

Research Objective: End stage renal disease (ESRD), a costly medical condition associated with substantial morbidity and mortality, can be prevented or delayed with effective management of chronic disease, particularly diabetes and hypertension. However, the uninsured have limited ability to finance health services and often forego preventive and chronic disease care. We examined the impact of Medicaid expansion on the incidence of ESRD in the non-elderly adult population.

Study Design: A quasi-experimental differences-in-differences study of the incidence rate of ESRD in the non-elderly adult population in the United States. We calculated quarterly incidence rates by geolocating incident patients within Public Use Microdata Areas (PUMAs), which are contiguous geographic areas of at least 100,000 persons nested within states. We estimated linear models comparing pre- versus post-expansion changes in the incidence rate in PUMAs in expansion versus non-expansion states. Models were adjusted for age group, sex, race/ethnicity, time-varying PUMA-level economic characteristics with fixed effects for year-quarter, season, and PUMA. To allow for a transitional period, the post-period was split into a transitional first year post-expansion and up to 3 years after the first post-expansion year. Robust standard errors accounted for clustering by state. We confirmed parallel pre-policy trends between expansion and non-expansion PUMAs.

Population Studied: An annual average of 194,793,035 persons aged 19-64 years in 2,351 PUMAs in the 50 states and DC from 2012 through 2017 from American Community Survey microdata. Over the study period 347,288 incident ESRD patients were identified using the ESRD Medical Evidence Form (CMS 2728) and geolocated within a PUMA.

Principal Findings: The mean quarterly ESRD incidence rate for the 19-64 population in 2012 and 2013 was 67.8 cases per million in expansion states and 78.5 cases per million in non-expansion states. While incidence increased in both expansion and non-expansion states over the study period, Medicaid expansion was associated with 1.7 fewer incident ESRD cases per million (95% CI: -3.28 to -0.17), relative to concurrent trends in non-expansion states. This observed effect represents a 2.5% relative reduction in incidence. These findings were robust to exclusion of early- and late-expanding states, and time-varying covariates. When the one-year post-expansion transitional period was not included in the model, Medicaid expansion was associated with 1.4 fewer incident cases per million (95% CI: -2.64 to -0.11), relative to non-expansion states. In triple-difference models, we did not find evidence that the effects of Medicaid expansion varied by age, sex, race/ethnicity, and baseline levels of poverty.

Conclusions and Implications: The ACA’s Medicaid expansions were associated with a small but meaningful reduction in incidence of ESRD in the non-elderly adult population. This study extends evidence of the positive health impacts of Medicaid expansion under the ACA. Reduction in the incidence of ESRD may be particularly important for states that have not yet expanded Medicaid due to their higher baseline incidence rate. The findings also demonstrate the potential for spending on expansions of Medicaid coverage to generate offsetting reductions in spending in the Medicare program, the primary payer for the ESRD population in the US.