Black Americans who live in neighborhoods with lower levels of income and education may age faster than their white neighbors, according to a new study. This can be true even when an individual Black person has a higher income or education level — underscoring the extent to which a person’s surroundings can impact their health.
The study, published Wednesday in PLOS ONE, builds on an emerging body of research that links faster biological aging, measured by a process called DNA methylation (DNAm), to low socioeconomic status — a phrase that encompasses education, income, and wealth. The University of Pennsylvania research team is the first to show how the neighborhood a person lives in can contribute to racial disparities in accelerated aging, even after controlling for individual socioeconomic status. Researchers found that living in a “deprived” neighborhood — one that includes a greater proportion of low-income residents, among other factors — explains 21% of the racial disparity in one DNAm measure.
It’s well-established that some individuals age at different paces than others, said Corey McMillan, an associate professor of neurology at the University of Pennsylvania and one of the paper’s co-authors. But the new study “addresses some of the environmental pressures that contribute to different paces of aging, which Black individuals are more often exposed to due to structural factors like environmental racism.”
This is the phenomenon known as “weathering” — the premature biological aging experienced by people in marginalized communities as a result of stressors like racism and poverty. It’s been linked to poorer health outcomes ranging from hypertension and mental illness to higher infant and maternal mortality. STAT reported last year on a study showing that the brains of Black Americans age faster than white or Hispanic adults, with signs of dementia appearing in MRI scans as early as mid-life.
The new study looked to better shed light on the environmental factors that contribute to weathering. Researchers found that PM2.5 pollution — the amount of very fine particulates in the air that are smaller than 2.5 microns in diameter — has a much larger impact on Black Americans’ accelerated aging than white Americans exposed to the same pollution. The researchers also looked at “neighborhood deprivation” — an index that measures, for example, the portion of people living in a certain neighborhood with less than 12 years of education or the percentage who don’t own a car or live in overcrowded housing units.
It’s unclear whether disparities in the impact of air pollution on aging can be attributed to Black participants being more susceptible to pollution or having more exposure in ways that are unaccounted for in this study, the authors note. Having a history of lung conditions or asthma — conditions that disproportionately affect communities of color — could make someone more vulnerable.
Moreover, lead author Isabel Yannatos said, “that cumulative effect of disadvantage and discrimination could lead to a greater amount of stress, which could lead to someone’s body not being able to cope with air pollution as well.”
Other factors that might affect people’s level of exposure to air pollution even while living in the same neighborhood include varying amounts of time spent outside, having an air conditioning unit or air filter, the type of job or home a person has, and how long they’ve lived in the neighborhood, said Yannatos, a neuroscience doctoral student at the University of Pennsylvania.
The study was focused on data on 2,960 Americans age 50 or older, drawn from the Health and Retirement Study, a longitudinal cohort study that surveys a representative sample of about 20,000 people across the U.S. A subset of those participants submitted a blood sample in 2016. Researchers analyzed those samples for patterns of DNA methylation, a biological process that can change DNA activity, such as levels of gene expression. Looking at DNAm data, surveys, and neighborhoods based on participants’ ZIP codes, researchers used two statistical approaches to analyze how neighborhood and environmental factors contributed to racial disparities in epigenetic aging.
There are other limitations in the study. A big one exists across the field of social epigenetics, the authors note: A lack of longitudinal DNAm data that follows participants over a longer period, not just at one point in time.
“You would expect that someone who’s lived in a poor area with a lot of exposure to air pollution their entire lives, they’re probably gonna look pretty different from someone who’s moved into the neighborhood recently,” said Gloria Huei-Jong Graf, a doctoral candidate in epidemiology at the Columbia Mailman School of Public Health, who was not involved in the study. “Especially if you think about, what if it’s a gentrifying neighborhood? And the people who are moving in are more well-off than the people who have traditionally lived there.”
The results in this type of place-based study are also not fully generalizable, according to Emily Shantz, a Ph.D. candidate who studies health geographies at the University of Waterloo. Social systems, with their unique sets of environmental, social, and cultural norms, work differently in different places, she told STAT via email.
Shantz noted it would be interesting to see similar studies in other neighborhoods and with other racial and ethnic groups across the country, to see whether there are changes in the effects on accelerated aging and how much each factor contributes to disparities.
“Human bodies don’t live in a vacuum — they are constantly interacting with all aspects of their environments,” she said. ”Based on decades of work by primarily Black feminist scholars, we know that identities and social circumstances are not additive — they inform one another.”
Future research using a more intersectional approach that reflects these nuanced experiences is also on the authors’ wish list. As important as it is to quantify how much environmental factors contribute to weathering, it’s crucial to recognize how other structural and social factors can affect the aging of marginalized groups like Black women differently, the authors note. These can include differences in the accessibility and quality of health care access, as well as other forms of discrimination and environmental racism.
“My hope is that, as a field and as a society, we really start thinking about these types of environmental and neighborhood factors … as one of the drivers of health in addition to individual-level things,” said Yannatos. Once the link between the neighborhood a person lives in and their individual health has been established, she hopes the groundwork will be laid for local and larger-scale policy interventions that may “prevent some of these health problems and health disparities from arising.”