Medicaid Expansion and US Mortality Rates During the COVID-19 Pandemic, 2018-2022.

Objectives. To examine the association of state Medicaid expansion status with mortality changes during the COVID-19 pandemic in the United States. Methods. Deaths among individuals 20 to 64 years of age in 3142 counties were identified from 2018 to 2022 mortality surveillance data. Age-adjusted mortality rates were calculated for each county and by cause of death. Changes in mortality rates before and after the onset of the COVID-19 pandemic (2018-2019 vs 2021-2022) in Medicaid expansion states relative to nonexpansion states were calculated after adjustment for county sociodemographic factors and state COVID-19 vaccination rates. Results. All-cause mortality rates increased in 2020-2021 nationwide and decreased slightly in 2022. Overall, the increase was slower in Medicaid expansion states, leading to a net decrease of 31.8 (95% confidence interval [CI] = 20.9, 42.8) deaths per 100 000 person-years associated with Medicaid expansion from 2018-2019 to 2021-2022. The decrease was largest for deaths from heart disease and liver disease and was observed across subpopulations stratified by sex, age, and race. Conclusions. Increases in mortality rates were slower in Medicaid expansion states than in nonexpansion states during the COVID-19 public health emergency, suggesting a protective effect of Medicaid expansion on population health during the pandemic. (Am J Public Health. 2025;115(6):890-899. https://doi.org/10.2105/AJPH.2025.308045).