Study finds widening gap in death rates between US areas that vote for Democratic rather than Republican party

Americans living in counties that voted Democratic during presidential elections from 2000 to 2016 experienced larger decreases in death rates than residents of counties that voted for a Republican candidate, finds a study published by The BMJ today.
 
The results show that the gap in overall death rates between Democratic and Republican counties increased more than sixfold from 2001 to 2019, especially for white populations, and was driven mainly by deaths due to heart disease, cancer, chronic lung disease, unintentional injuries, and suicide.
 
The researchers suggest that this widening gap may reflect the influence of political environments on social, economic, and health policies.
 
Previous studies have shown that US counties that elect Republican candidates tend to experience worse health outcomes. However, recent trends in mortality differences for residents of Republican and Democratic counties are not known, nor are the conditions that might be driving those changes.
 
To address this uncertainty, a team of researchers set out to assess recent trends in age adjusted mortality rates (AAMRs) in the United States based on county level presidential voting patterns.
 
Their findings are based on data from the Centers for Disease Control and Prevention linked to county level data on US presidential elections. County political environment was classified as either Democratic or Republican for the four years that followed a November presidential election.
 
The researchers also repeated the analysis looking only at counties that voted exclusively Democratic or Republican throughout the two decades as well as performing an analysis using state governor election results as opposed to presidential elections.
 
The overall study period covered five presidential elections from 2000 to 2019 and included data for 99.8% of the US population. 
 
Between 2001 and 2019, mortality rates decreased by 22% in Democratic counties (from 850 to 664 per 100,000), but by only half that (11%) in Republican counties (from 867 to 771 per 100,000).
 
Consequently, the gap in mortality rates between Republican and Democratic counties jumped by 541%, from 16.7 per 100,000 in 2001 to 107 deaths per 100,000 in 2019. 
 
Over the study period, male and female residents of Democratic counties experienced both lower mortality rates and twice the relative decrease in mortality rates than their counterparts in Republican counties.
 
Black Americans experienced largely similar improvement in age adjusted mortality rates in both Democratic and Republican counties throughout the study period though residents of Democratic counties did appear to do better.
 
However, the mortality gap between white residents in Democratic versus Republican counties increased fourfold, from 25 to 101 per 100,000. As such, white residents in Democratic counties experienced 15% lower mortality rates in 2019 than white residents in Republican counties compared with just 3% in 2001.
 
Hispanic Americans had lower mortality rates than either white or black Americans, but there was little gap between those residing in Democratic versus Republican counties.
 
Rural Republican counties experienced the highest mortality rates and the least improvement over the study period, suggesting that the political environment has an important role to play in the widening urban-rural mortality gap, say the researchers.
 
The rising mortality gap between Republican and Democratic counties over the study period was largely driven by deaths due to heart disease, cancer, chronic lung disease, unintentional injuries (including drug overdoses), and suicide. 
 
This is an observational study so can’t establish cause, and the authors highlight some limitations. For example, they denoted political environment dichotomously based on the party receiving the majority vote, rather than a continuous measure such as vote share, or margin. It is also possible that poor health or social and economic factors that lead to poor health also motivate political preference.
 
However, trends were similar when comparing counties that did not switch political environment throughout the study period and when state governor election results were used, suggesting that the findings are robust.
 
As such, they conclude: “Overall, our finding that Democratic counties have experienced steeper declines in mortality than Republican counties over the past two decades builds upon previous evidence suggesting that more liberal policies, laws, and regulations may be associated with better health outcomes.”
 
And they call for further research “to better elucidate factors driving this widening difference in mortality rates between Republican and Democratic counties, to inform clinical, public health, and policy strategies to improve the health of all Americans.”
 
This study adds to mounting evidence of a link between political party affiliation and death rates and of worrisome trends associated with more conservative policies sweeping the nation, says Steven Woolf at Virginia Commonwealth University in a linked editorial. 
 
He notes that Republican-led legislatures in dozens of state capitols are passing laws to undermine health and safety regulations, ban abortion, limit LGBT+ rights, and implement more conservative policies on voting, school curriculums, and climate policy.
 
To understand the implications for population health, researchers must break with custom, he writes. “Although scientific literature has traditionally avoided discussing politics, the growing influence of partisan affiliation on policies affecting health makes this covariate an increasingly important subject of study.”