ANN ARBOR—A new University of Michigan study finds that over the last half century U.S. infant mortality rates are associated with the political party that holds the presidency, dropping relative to trend under Democrats and rising under Republicans.

The study was published online late last year by the International Journal of Epidemiology, and is spurring a lively debate, with two commentaries and a response from the authors just published by the journal.

U-M researchers Javier Rodriguez, John Bound and Arline Geronimus investigated whether the political party of the president was associated with infant mortality as part of a larger program of research meant to shed light on why infant mortality rates in the U.S.—the wealthiest nation in the world—exceed not only those of all other developed countries but also those in many less developed countries.

Earlier studies around the world have examined how different types of political and economic regimes and policies affect a variety of public health outcomes, either directly or indirectly.

For the analysis, the authors used data on infant mortality from the U. S. National Vital Statistics Reports from 1965 through 2010, beginning with the administration of Lyndon Johnson and ending halfway through Barack Obama’s first term—across nine presidential administrations.

This post-Civil Rights Movement era spans the South’s shift to the Republican Party, the introduction of Great Society programs and increasing party polarization. It also covers the introduction of important technological and therapeutic innovations that can dramatically improve the survival of babies born too soon or too small if they have access to them.

Overall, they found that over the past 46 years infant mortality rates in the U.S. have declined dramatically, dropping 75 percent from 24.7 per 1,000 live births in 1965 to 6.1 per 1,000 live births in 2010. Infant mortality rates for African-Americans, however, remain more than twice what they are for whites.

The researchers used statistical techniques to control for the overall trend of decreasing mortality and a wide range of factors other than presidential party affiliation that could affect infant mortality. These included the poverty rate, education, unemployment, income, income inequality and health-relevant behaviors like smoking.

After controlling for all these factors, they found that infant mortality rates were about 3 percent higher, relative to trend, during a typical Republican presidential year, compared with a typical Democratic one. This was the case nationwide and for black or white infant mortality rates separately.

To put the magnitude of these findings in context, researchers have estimated that the introduction of Medicaid led to a 4 percent decline in black infant mortality rates.

The authors acknowledge that there may be unknown factors that are responsible for the patterns they have uncovered and call for more research to determine whether the association they have uncovered is causal and to identify the mechanisms involved.

Related Links:

• Full study: http://ije.oxfordjournals.org/content/early/2013/12/30/ije.dyt252.full
• Commentary by Danny Dorling, Oxford University: http://ije.oxfordjournals.org/content/early/2014/02/06/ije.dyu040.full
• Commentary by Ralph Catalano, University of California-Berkeley: http://ije.oxfordjournals.org/content/early/2014/01/17/ije.dyt273
• Response by the U-M researchers to the commentaries: http://ije.oxfordjournals.org/content/early/2014/02/06/ije.dyt284