Abstract
Despite gains in overall life expectancy in the United States between 1961 and 1999, the life expectancy of a significant segment of the population is actually declining or, at best, stagnating, according to research from IHME. The study, The reversal of fortunes: trends in county mortality and cross-county mortality disparities in the United States, is the first to look at mortality trends in the US by county over such a long period of time. The work was done in collaboration with scientists at the Harvard School of Public Health.
Research findings
The researchers found that between 1961 and 1999, average overall life expectancy in the US increased from 66.9 to 74.1 years for men and from 73.5 to 79.6 for women. When looking at individual counties, however, the researchers found that beginning in the 1980s, the best-off counties continued to improve, but there was stagnation or worsening of life expectancy in the worst-off counties, where 4% of the male population and 19% of the female population experienced either decline or stagnation in mortality. In the best-off counties, men lived 9.0 years longer than those in the worst-off counties in 1983; by 1999 that gap had increased to 11.0 years. For women, the 1983 life expectancy gap of 6.7 years increased to 7.5 years by 1999.
The majority of the counties that had the worst downward swings in life expectancy were in the Deep South, along the Mississippi River, and in Appalachia, extending into the southern portion of the Midwest and into Texas. The researchers also analyzed data on deaths from different diseases and showed that the stagnation and worsening mortality was primarily a result of an increase in diabetes, cancers, and chronic obstructive pulmonary disease, combined with a slowdown or halt in improvements in cardiovascular mortality. An increase in HIV/AIDS and homicides also played a role for men, but not for women.
Analytical approach
The researchers analyzed mortality data from the National Center for Health Statistics and population data from the US Census Bureau to estimate sex-specific life expectancy for US counties for every year between 1961 and 1999. Metrics of cross-county mortality disparity were calculated, and counties were grouped based on whether their mortality changed favorably or unfavorably relative to the national average. Probability of death was also estimated from specific diseases for counties with above- or below-average mortality performance.
Research objective
One of the major aims of the US health system is improving the health of all people, particularly those segments of the population at greater risk of health disparities. While average life expectancy overall in the US has increased in the last 40 years, evidence indicates that these health gains may not be distributed evenly. This study capitalizes on the benefits of county-level analysis: counties are the smallest measurable unit for which mortality data are available, county-level data allow analyses for small subgroups of the US population, and availability of county-level socioeconomic and cause-specific mortality data allow analysis of trends in all-cause and disease-specific mortality in relation to county environmental and socioeconomic characteristics. With this county-level data, researchers can provide insight into trends in mortality and mortality disparities in US counties for a period of approximately four decades, one of the longest trend analyses of mortality disparities in the US. This research is part of ongoing work by IHME to provide timely, accurate, and comparable health measurements.
Recommendations for future work
Life expectancy decline among some US counties highlights the relative geographic disparities that continue to exist in subpopulations of the United States. The role of risk factors such as smoking, high blood pressure, and obesity in life expectancy should be further investigated, and programs that increase the coverage of interventions for chronic disease and injury risk factors in the worst-off counties, states, and regions should be established and regularly monitored and evaluated with respect to their local, versus aggregate only, impacts.
