A Precision Public Health Study on the Divergence of Life Expectancies Over Time in United States Counties

Ensuring healthy lifespans and promoting equity in health outcomes is a critical component of the United Nations Sustainable Development Goals, and progress has largely been measured using national life expectancy averages. While national averages reveal broad trends over time, they also largely obscure differences and inequalities at the subnational level. In studies of sustainability and public health, divergence refers to the increasing difference between two values over time. A major topic of interest is how subnational units, such as counties, deviate from the national average over time. In this work, we examined how three factors critical to evaluating the health of communities and quality of life, namely life expectancy, education, and income, have deviated in the United States at the county level in comparison to the national average. We found that while deviations in income and education have remained largely constant, the life expectancies of some counties have increased significantly over the national average, while others have stalled or even decreased in comparison. There has been a systematic divergence in life expectancies in US counties over a 34-year period leading to increasing disparities between counties. Gains in life expectancy were primarily concentrated in metropolitan areas while rural counties lagged, increasing urban-rural disparities over time. Identifying the upward or downward trends in life expectancy at the county level and understanding the root causes and risk factors driving those trends is critical to formulating customized Precision Public Health interventions and policies to improve health outcomes and create sustainable communities.