In this issue of JAMA Internal Medicine, there is a timely and important study about the association between eligibility for Medicare at age 65 years and racial and ethnic disparities in access to care and health in the US.1 Using the “natural experiment” of Medicare eligibility, a regression discontinuity design, and information from 2 federal databases, Wallace and colleagues1 found that immediately after age 65 years, disparities between White and Black adults and between White and Hispanic adults sharply decrease. After age 65 years, there were marked reductions in the share of the population that was uninsured, without a usual source of care, unable to see a physician in the past year owing to cost, and in poor self-reported health.