BAmericans living in neighborhoods with lower incomes and education may age faster than their white neighbors, according to a new study. This may even be the case when an individual black person has a higher income or higher level of education, underscoring the extent to which an individual’s environment can affect their health.
The study, published Wednesday in PLOS ONE, builds on an emerging study 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 a person’s neighborhood may contribute to racial disparities in accelerated aging, even after adjusting for individual socioeconomic status. Researchers found that living in a “disadvantaged” neighborhood — one that includes a higher proportion of low-income residents — explains 21% of racial disparity in one DNAm measure.
It’s common knowledge that some people age at a different rate 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 rates of aging, which black individuals are more likely to be exposed to because of structural factors such as environmental racism.”
This is the phenomenon known as “weathering” – the premature biological aging people in marginalized communities experience due to stressors such as racism and poverty. It has been associated with worse health outcomes ranging from hypertension and mental illness higher infant and maternal mortality. STAT reported last year on a study showing that the brains of black Americans are aging faster than white or Hispanic adults, with signs of dementia showing up on MRI scans as early as middle age.
The new study seemed to shed better light on the environmental factors that contribute to weathering. Researchers found that PM2.5 pollution — the amount of very fine particles in the air smaller than 2.5 microns in diameter — has a much greater impact on the accelerated aging of black Americans than white Americans exposed to the same pollution. The researchers also looked at “neighborhood backlog— an index that measures, for example, the proportion of people living in a given neighborhood with less than 12 years of education or the percentage who do not own a car or live in overcrowded housing units.
It’s unclear whether differences in the impact of air pollution on aging can be attributed to black participants being more susceptible to pollution or to more exposure in ways not mentioned in this study, the authors note. Having a history of lung disease or asthma — conditions that disproportionately affect communities of color — can make a person more vulnerable.
In addition, lead author Isabel Yannatos said, “that cumulative effect of deprivation and discrimination can lead to increased stress, which can lead to a person’s body being unable to handle air pollution as well.”
Other factors that can affect people’s exposure to air pollution, even if they live in the same neighborhood, include the amount of time spent outside, having an air conditioner or air filter, the type of job or home that someone has and how long they’ve lived in the area, said Yannatos, a neuroscience doctoral student at the University of Pennsylvania.
The study focused on data on 2,960 Americans age 50 or older, drawn from the Research on health and retirement, a longitudinal cohort study examining a representative sample of approximately 20,000 people in the US. A subgroup of those participants submitted a blood sample in 2016. Researchers analyzed those samples for patterns of DNA methylation, a biological process that can alter 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 differences in epigenetic aging.
There are other limitations in the study. A big one exists in the field of social epigenetics, the authors note: a lack of longitudinal DNAm data that follows participants over a longer period of time, not just at a point in time.
“You would expect that someone who has lived in a poor area all their life with a lot of exposure to air pollution would probably look very different from someone who has recently moved to the area,” says Gloria Huei-Jong Graf, a PhD student epidemiology at the Columbia Mailman School of Public Health, who was not involved in the study. “Especially when you consider, what if it’s a gentrifying neighborhood? And the people who come to live there have it better than the people who have traditionally lived there.”
According to Emily Shantz, a Ph.D. candidate studying health geographies at the University of Waterloo. Social systems, with their unique sets of environmental, social and cultural norms, operate differently in different places, she told STAT via email.
Shantz noted that it would be interesting to see similar studies in other neighborhoods and with other racial and ethnic groups across the country to see if there are any 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 environment,” she said. “Based on decades of work by mostly black feminist scholars, we know that identities and social conditions are not additive — they inform each other.”
Future research with 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 is crucial to recognize how other structural and social factors may differently affect the aging of marginalized groups such as black women, the authors note. These can be differences in the accessibility and quality of access to health care, but also other forms of discrimination and environmental racism.
“My hope is that as a field and as a society, we really start thinking about these kinds of environmental and neighborhood factors… as one of the drivers of health in addition to individual-level issues,” Yannatos said. Once the link between the neighborhood someone lives in and their individual health is established, she hopes it will lay the groundwork for local and large-scale policy interventions that “could prevent some of these health problems and health inequalities from developing.”