Two recent papers in The Lancet Public Health, authored by Miller School Ph.D. alumnus Samuel L. Swift, Ph.D., and colleagues, examine the association between unsecured debt in early adulthood and long-term exposure to poverty with premature mortality among adults in the United States.

In one of the new Lancet Public Health articles, Dr. Swift and colleagues used data from the National Longitudinal Survey of Youth 1979 to follow nearly 7,000 participants over more than three decades. They identified distinct trajectories of unsecured debt in early adulthood, including constant low debt, constant medium debt, increasing debt, and no debt, and then examined how those patterns related to premature mortality in midlife.

The team found that adults whose unsecured debt increased over early adulthood had a substantially higher risk of premature mortality compared with those who maintained low levels of unsecured debt. Notably, individuals with no unsecured debt also appeared to be at elevated risk in unadjusted analyses, suggesting that the absence of debt may, for some, reflect exclusion from financial systems rather than financial stability.

A companion paper extended this work by examining cumulative exposure to poverty during adulthood, again finding that greater exposure was associated with a higher risk of premature mortality.

Together, the studies add longitudinal, nationally representative evidence to a growing body of research linking financial strain to health outcomes.

A Path Shaped at the Miller School

Dr. Swift traces his development as a social epidemiologist back to his training as a Ph.D. student at the University of Miami Miller School of Medicine.

“I had an amazing experience at the University,” he said. “I still work to this day with my mentor, Dr. Adina Zeki Al Hazzouri, who ignited my passion for causal inference and social epidemiology. She remains a person I greatly respect and look up to this day.”

He also emphasized the depth of methods training he received during his doctoral studies. “I received excellent stats and epidemiology training from Drs. Hlaing, Koru-Sengul, Wang, Balise, Florez, Feaster, Reis, Elfassy, and Bailey. I would like to thank them for helping me to get to where I am now.”

That foundation in rigorous epidemiologic methods and causal inference positioned him to ask complex questions about how social and economic systems shape risk over the life course.

Debt as a Social Determinant of Health

Dr. Swift’s interest in unsecured debt emerged from both personal observation and scholarly work on the social meaning of financial obligations.

“The thing that got me most interested in debt and social epidemiology more broadly was the aftermath of the 2008 Great Recession, and what I believe are lasting health consequences in the United States reflected in our stagnated life expectancy,” he said.

He also points to the influence of anthropologist David Graeber’s book Debt: The First 5,000 Years. “In this book, Dr. Graeber explains that debt reflects our social contract; in other words, it is a system we use to say who deserves trust, respect, and resources in society,” Dr. Swift said. “Some of the richest people on earth hold the most debt, which reflects the enormous trust that society puts in these people.”

For the Lancet Public Health work, the team focused on unsecured debt, such as credit cards, payday loans, and certain types of personal loans, which typically carry high interest rates and do not directly build wealth.

“While secured debt like mortgages builds wealth, unsecured debt (the type we studied), like payday loans and credit card debt, can be a tool used to extract resources from lower-income persons, increasing financial insecurity,” Dr. Swift said. “For me, debt is a complex and fascinating social determinant of health.”

What “No Debt” Can Mean in an Unequal System

One of the most striking patterns in the study was the finding that having no unsecured debt was not always a marker of stability.

“That was the most interesting part of the paper,” Dr. Swift said. While the higher risk of premature mortality in the no-debt group was not statistically significant after adjustment, the pattern raised important questions.

“We posit that the ‘no debt’ group was worse than the ‘low debt’ group for exactly that reason, being completely locked out of the system, to where you are not even able to take out credit cards or loans, is also dangerous,” he said. “So, being able to take on some debt may reflect that you have access to some resources, while high unsecured debt may reflect increased poverty and financial instability.”

In that sense, both increasing unsecured debt and complete exclusion from credit systems can signal structural disadvantage and heightened health risk.

Policy, Prevention, and the Role of Public Health

Dr. Swift views the findings within a broader discussion about poverty as a fundamental cause of poor health in the United States.

“This is a big question,” he said when asked about potential solutions. “I will start by saying I believe poverty is a fundamental cause of poor health in the United States, and that there are interventions spanning political ideology on how we should address this.”

“When I look at the public health literature, I see good evidence that policies promoting increased access to affordable housing, healthcare, food, education, and higher wages are all anti-poverty and pro-public health policies,” he continued.

Specific to unsecured debt, he notes that states have experimented with anti-predatory lending laws and interest rate caps on certain loans. “There is some literature on anti-predatory lending laws, and many states have caps on interest rates on certain types of loans. I think more research on those laws is needed, and I hope to do some of that research myself in the coming years.”

Advice for Emerging Researchers

For current students and trainees who want to study social and economic drivers of health, Dr. Swift encourages looking beyond traditional disciplinary boundaries.

“Read literature from other fields!” he said. “For me, learning a little economics (I am no expert) has really helped my thinking. I also recommend learning the history of social movements and social science research because there are literally hundreds of years of thought on these topics, and nothing we do is devoid of that context.”

His work illustrates how bringing together rigorous epidemiologic methods, economic concepts, and social theory can generate new insights into how financial systems influence who lives — and who dies — prematurely.

Written by Deycha Torres Hernández, published on December 12, 2025.