Where you live has an increasingly greater impact on how long you live. This fact may stem largely from regional health policies and health-related behaviors that have been in place – or absent – for decades.

A new paper coauthored by Federal Reserve Bank of Boston senior economist and policy advisor Christopher Foote notes that across U.S. states, inequality in mortality increased by about 70% from 1992 to 2016. Like a recent report from the National Academies of Sciences, Engineering, and Medicine, Foote and his coauthors measure mortality rates at midlife, defined as ages 25 to 64. One of their key findings is that the increase in state-level inequality in midlife mortality is related to state-level differences in average incomes. High-income states have seen continued improvement in midlife mortality during the past three decades, while improvements in low-income states have lagged behind.

The authors contend that differing health policies and behaviors across states are a likely source of the rising income-mortality correlation. “The most promising explanation for our findings involves efforts by high-income states to adopt specific health-improving policies and behaviors since at least the early 1990s,” the authors write. “Over time, these efforts reduced mortality in high-income states more rapidly than in low-income states,  leading to widening spatial disparities in health.”

The paper, titled “Rising Geographic Disparities in US Mortality,” was published earlier this month in the Journal of Economic Perspectives. Foote’s coauthors are Harvard University T.H. Chan School of Public Health professor Ellen Meara, Dartmouth College research professor Jonathan Skinner, former Boston Fed senior research assistant Benjamin Couillard (now a Ph.D student in economics at the University of Toronto), and Boston Fed senior research assistant Kavish Gandhi.

The paper’s findings are based on state-level data on mortality, income, health behavior (as measured by smoking and obesity rates), and health-care quality from 1992 through 2016. Because the authors study mortality trends over many decades, their findings likely reflect cumulative effects of health determinants over people’s entire lives, or from when they entered adulthood.

The authors link their findings to numerous previous studies that have analyzed the effects of separate health policies, such as the introduction of Medicaid and the opening of community health centers. The evidence suggests that health policies have significant beneficial effects on the populations they serve, so the differential adoption of policies across states is potentially linked to widening disparities in health outcomes.

The effects of health policies are distinct from – but complementary to – the effects of health-related behaviors, which also differ across states. In the early 1970s, economist Victor Fuchs noted that life expectancy in Utah was much higher than in neighboring Nevada, a fact that Fuchs attributed to the healthier behavior of Utah residents. If high-income states were more likely to adopt healthy behaviors during the past several decades, then these choices could have also contributed to the rising income-mortality correlation.

Alternative explanations include deaths of despair, differing education levels, and widening income inequality

The authors relate their findings to several strands of recent research, including analyses of U.S. life expectancy. After rising steadily from the 1960s through the early 2000s, Americans’ life expectancy leveled off for about a decade and then fell slightly after 2014. Previous research links this pattern to stalled progress against heart disease and other major causes of death. Existing research also points to an increase in the number of deaths from suicide, drug overdose, and alcohol-related causes – so-called deaths of despair – as contributing to the plateau in life expectancy.

The authors confirm that deaths of despair have risen dramatically in recent years, but even now such deaths account for only about one-sixth of all midlife deaths. The authors find that other, more common causes of death, such as cancer, are behind the state-level disparities in mortality that they identify.

A second theme of existing research is the rising gap between life expectancy of college graduates and persons without four-year degrees. U.S. death certificates began recording the educational attainments of decedents in the early 1990s, and it is now well-known that mortality rates among the non-college population have risen sharply relative to mortality among college grads.

This pattern suggests that a possible explanation for the rising correlation between state-level income and mortality is that college graduates are becoming more concentrated in high-income states. The authors rule out this possibility, noting that virtually all of the increase in health inequality remains after state-level differences in college attainment are accounted for.

Finally, the authors relate their findings to rising income inequality across states. From the late 1920s until the early 1980s, average state-level incomes converged, due largely to large income gains enjoyed by Southern states, which began the 20th century relatively poor. Since the early 1980s, however, convergence in income has stalled, and state-level incomes have started moving apart.

The authors find that states where incomes grew the most since the 1980s did not enjoy the largest mortality improvements. Rather, the average level of income of the state over many decades, relative to average incomes of the other states, has the largest effect on mortality. This fact suggests that the ability of traditionally high-income states to adopt good policies and behaviors explains the rising correlation between mortality and income at the state level.

The authors hypothesize that rising inequality in midlife mortality and the tightening mortality-income correlation are the long-run effects of health determinants that have varied across states for many years. “The data suggest that residents of high-income states have enacted policies and adopted behaviors with long-run payoffs to midlife mortality that are becoming increasingly apparent over time,” they write.

Read the paper.