A major study led by researchers from Yale School of Public Health (YSPH) has uncovered significant differences in life expectancy across U.S. states and the District of Columbia over the last hundred years.
Published in JAMA Network Open, the study highlights how public health policies, social conditions, and environmental factors have deeply influenced how long people live, depending on where they are born and live.
The research team, which included experts from Yale, the University of Michigan, and the University of British Columbia, analyzed over 179 million deaths from 1969 to 2020. To better understand how life expectancy has changed over time, they studied people based on the year they were born, rather than just looking at yearly death rates.
This approach, called the age-period-cohort model, allowed the researchers to track the health experiences of specific generations, offering a clearer picture of how policies and living conditions shaped people’s lives as they aged.
The findings were striking. While some states saw major improvements in life expectancy, others lagged behind. For example, in Southern states like Mississippi, Alabama, and Kentucky, life expectancy barely increased for women between 1900 and 2000—less than three years of added life over an entire century.
In contrast, women in states like New York and California saw their life expectancy rise by more than 20 years during the same period.
The study also highlighted Washington, D.C., which experienced dramatic changes. In 1900, D.C. had the lowest life expectancy in the United States. But by 2000, life expectancy for women had improved by 30 years, and for men by an astonishing 38 years. Researchers suggest that changes in urban policies and shifting demographics contributed to this major turnaround.
In states with the lowest gains, researchers pointed to factors like poverty, limited access to health care, and weaker public health systems as major reasons for the poor outcomes.
Dr. Jamie Tam, a co-author of the study, noted that the health policies and economic conditions of a state greatly affect its residents’ life expectancy. States with high poverty rates and limited health care access were found to have smaller improvements in life expectancy.
The researchers used a special method to separate the effects of aging, historical events, and generational influences on death rates. This allowed them to see how things like sanitation, vaccinations, and exposure to tobacco during a person’s early years could impact their health decades later.
Lead author Dr. Theodore R. Holford explained that studying life expectancy by generation gives a more accurate view of how public health measures and social changes affect long-term health. For example, states like California that adopted smoke-free laws early on saw much better health outcomes compared to states with fewer restrictions on tobacco.
The study also looked at how quickly the risk of death doubled after age 35. States like New York and Florida showed slower increases in death rates, which suggests people were aging more healthily. Meanwhile, states like Oklahoma and Iowa had faster increases, indicating poorer health outcomes as people aged.
For men born after 1950 in many Southern states, life expectancy gains came to a halt, increasing by less than two years. In contrast, states like Hawaii and Massachusetts consistently led the nation in life expectancy for both men and women.
Dr. Holford pointed out that these differences are not just accidents of history—they are the result of decades of health policies and investments in public health. Without meaningful changes, he warned that these health gaps could continue or even worsen.
The researchers hope that their findings will encourage policymakers to take action to close the life expectancy gap across the country. Dr. Tam added that understanding health through a generational lens can help leaders see how early public health decisions can benefit people for decades.
For example, California’s early adoption of smoke-free laws not only improved health outcomes for those living there but also set a standard that other states followed. In places where such policies were not implemented, smoking-related deaths remain high.
The study’s authors argue that investing in public health and strong health policies is crucial for reducing these long-term disparities. States that fail to prioritize public health may continue to see poor health outcomes, while those that make it a priority could enjoy longer, healthier lives for their residents.
The findings suggest that early interventions, such as stronger tobacco regulations and better access to health care, could make a significant difference in life expectancy across the United States.
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The research findings can be found in JAMA Network Open.
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