Wisconsin experience indicates that expanding public insurance to low-income childless adults has health care impacts.

As states consider expanding Medicaid to low-income childless adults under the Affordable Care Act, their decisions will depend, in part, on how such coverage may affect the use of medical care. In 2009 Wisconsin created a new public insurance program for low-income uninsured childless adults. We analyzed administrative claims data spanning 2008 and 2009 using a case-crossover study design on a population of 9,619 Wisconsin residents with very low incomes who were automatically enrolled in this program in January 2009. In the twelve months following enrollment in public insurance, outpatient visits for the study population increased 29 percent, and emergency department visits increased 46 percent. Inpatient hospitalizations declined 59 percent, and preventable hospitalizations fell 48 percent. These results demonstrate that public insurance coverage expansions to childless adults have the potential to improve health and reduce costs by increasing access to outpatient care and reducing hospitalizations.