We compared three states that substantially expanded adult Medicaid eligibility since 2000 (New York, Maine, and Arizona) with neighboring states without expansions. The sample consisted of adults between the ages of 20 and 64 years who were observed 5 years before and after the expansions, from 1997 through 2007. The primary outcome was all-cause county-level mortality among 68,012 year- and county-specific observations in the Compressed Mortality File of the Centers for Disease Control and Prevention. Secondary outcomes were rates of insurance coverage, delayed care because of costs, and self-reported health among 169,124 persons in the Current Population Survey and 192,148 persons in the Behavioral Risk Factor Surveillance System.

This comes from the description of methods of a recent article in the New England Journal of Medicine. The article was mentioned by the New York Times on July 26. I like the plots in Figure 1.

The Times provides some context as to why it is seen as “controversial” whether Medicaid expansions positively impact health outcomes:

Medicaid expansions are controversial, not just because they cost states money, but also because some critics, primarily conservatives, contend the program does not improve the health of recipients and may even be associated with worse health. Attempts to research that issue have encountered the vexing problem of how to compare people who sign up for Medicaid with those who are eligible but remain uninsured. People who choose to enroll may be sicker, or they may be healthier and simply be more motivated to see doctors.

See also earlier post.