August 26, 2024—Nancy Krieger, professor of social epidemiology at Harvard T.H. Chan School of Public Health, has conducted research at the intersection of social justice, science, and health for more than three decades. Below, she discusses her most recent study, published in JAMA Network Open, about epigenetic aging and racial, economic, and environmental injustice.
Q: What were you exploring in this study and what did you find?
A: Our big question was: Are early and adult life exposures to racial, economic, and environmental injustice tied to accelerated aging and increased risk of premature mortality?
We explored this question by studying participants’ epigenetic age—otherwise known as their biological age, which can differ from chronological age—and their socioeconomic conditions during infancy and early childhood. Epigenetic age can be ascertained from modifications to DNA that affect gene expression but do not alter the underlying sequence of genes, and these modifications can be detected using blood samples.
We had obtained blood samples from more than 1,000 participants enrolled in a previous study I’d led, called My Body, My Story. This study, focused on racism and risk of cardiovascular disease, included only U.S.-born Black and white participants between the ages of 35 and 64. We identified their epigenetic ages to determine who did or didn’t experience epigenetic age acceleration, that is, had an epigenetic age older than their chronological age. We then examined the relationships between epigenetic accelerated aging and exposure to diverse types of racialized, economic, and environmental injustice during participants’ early life, such as where they were born (including in a previously Jim Crow state or not); their birth states’ levels of conservatism at the time of their birth, measured by policies; and their parents’ educational level. We also examined current exposures to fine particulate air pollution; neighborhood poverty and racial segregation; and household poverty. We then repeated our study among the more than 6,000 participants enrolled in another study, the Multi-Ethnic Atherosclerosis Study, in order to see if our results held across a different population.
One of our key findings was significant accelerated epigenetic aging among Black participants who were born in a state enforcing Jim Crow laws during the time Jim Crow was legal and/or who were born in a state with a high level of political conservatism at the time of their birth—as indicated by more conservative policies pertaining to abortion, criminal justice, drugs and alcohol, education, the environment, civil rights, gun control, labor, social welfare, and taxation. We also observed accelerated epigenetic aging across all participants, regardless of racialized group, who were born to households with low parental education, a measurement that suggests low economic resources.
Q: What are the major takeaways?
A: Our findings could provide a pathway to understand why some groups die at earlier ages than others from the same illnesses. They suggest that racial and economic injustice have an impact on the likelihood that someone biologically ages faster and is therefore at higher risk of premature mortality from chronic diseases, usually from cardiovascular and other cardiometabolic diseases.
Another takeaway is the importance of remembering that there’s no way to live disembodied. Among academics, policymakers, journalists, and many others, there is rightly a lot of concern about how present-day societal conditions impact health. But people don’t just suddenly have a body today. They embody the conditions in which they were born and in which they grew up. To understand an individual’s health status and risk of premature mortality, you need to understand not just their present, but also their past. That applies on a population level as well. To understand health inequities, we need to remember that there are many, many people alive today—anyone in their sixties and older in the U.S.—who were born when Jim Crow was legal. That matters to our current day. It isn’t ancient history or even the distant past.
Q: How do you think these findings could be used by researchers or policymakers?
A: Our study can clearly speak to those working on policies around reparations and poverty alleviation. But rather than having immediately obvious and easy policy implications, I would say the study is more meant to begin expanding understanding. Our results are thought-provoking; I would never claim they’re definitive. They’re a start. Our findings can inspire and encourage others to collect more evidence on epigenetic aging and social justice or injustice, especially given that we now have improved technology to do so. Such embodied evidence can help inform efforts to bring us closer to a society in which people can live lives that are as healthy as possible, unmarred by injustice.
Photos: iStock: Onuchcha; courtesy of Nancy Krieger