A major new study led by researchers at the Yale School of Public Health (YSPH) has revealed striking disparities in life expectancy across U.S. states and Washington, D.C., spanning more than a century. This comprehensive research, published in JAMA Network Open, highlights how regional public health policies, social conditions, and environmental factors have profoundly shaped life outcomes. The study analysed over 179 million deaths from 1969 to 2020, focusing on birth cohort trends rather than the more conventional year-by-year mortality rates. This approach provides a clearer view of how entire generations have experienced health over time, capturing the long-term effects of policies and living conditions.
One of the key findings is the significant variation in life expectancy gains between different regions. States in the Northeast, the West, and Washington, D.C. have generally experienced the most important improvements. For example, the nation’s capital, which had the lowest life expectancy for the 1900 birth cohort, saw remarkable gains, with life expectancy for women increasing by 30 years and for men by 38 years by 2000. In stark contrast, several Southern states, including Mississippi, Alabama, and Kentucky, reported minimal improvements over the same period, particularly for women. This divergence highlights the long-term impact of local health policies, economic conditions, and social environments.
Lead author Theodore R. Holford, the Susan Dwight Bliss Professor Emeritus of Biostatistics at YSPH, emphasised the value of using a birth cohort approach, which captures the cumulative effects of policies and social conditions that might otherwise be masked in traditional year-by-year mortality data. “Looking at mortality trends by cohort gives us a more accurate reflection of the lived experiences of populations,” Holford said. This method allows researchers to consider how early-life exposures, such as access to clean water, sanitation, vaccinations, and tobacco use, influence long-term health outcomes. It also accounts for the lasting impacts of historical events like economic recessions, public health campaigns, and environmental regulations.
The study’s findings also underscore the role of state-level health policies in shaping life expectancy. For instance, California’s early adoption of smoke-free workplace laws in 1995 led to substantial public health gains, significantly reducing smoking-related mortality over time. In contrast, states like Kentucky, which have been slower to implement similar tobacco controls, continue to face higher smoking rates and associated health problems. This contrast highlights how proactive public health measures can transform population health outcomes, reducing the long-term burden of chronic diseases.
Moreover, the researchers examined the rate at which mortality increased after age 35, using a measure known as doubling time — the period it takes for an individual’s risk of death to double. They found that states like New York and Florida, which have implemented more comprehensive public health initiatives, exhibited slower mortality escalations, reflecting healthier ageing. In comparison, states like Oklahoma and Iowa experienced much faster mortality increases, emphasising the importance of sustained health investments over the life course.
Ultimately, the authors hope their findings inspire policymakers to address the deeply entrenched health disparities that still divide the United States. They argue that without conscious efforts to expand healthcare access, strengthen public health systems, and reduce economic inequality, these gaps in life expectancy will persist or even widen. Holford pointed out, “Where you are born shouldn’t determine how long you live. But in America, it still does.” This research offers a powerful reminder that the health of future generations depends on the choices made today.
More information: Theodore R. Holford et al, All-Cause Mortality and Life Expectancy by Birth Cohort Across US States, JAMA Network Open. DOI: 10.1001/jamanetworkopen.2025.7695
Journal information: JAMA Network Open Provided by Yale University
