What Explains the Association Between Historic Redlining and… : Neurology Today

Article In Brief

People who live in neighborhoods that were subject to historic redlining have experienced a greater risk for community-level cardiovascular health morbidities and specifically stroke prevalence, disproportionately affecting racial and ethnic minority communities. Experts offer strategies for addressing the disparities in outcomes and the social factors that lead to greater risk for poor brain health.

Historical redlining is independently associated with community-level stroke risk among New York City residents, beyond recognized social determinants of health (SDOH), according to a study published in April in JAMA Network Open.

The study adds to a growing body of evidence from research conducted in communities across the United States that all point to the same conclusion: redlining is toxic to cardiometabolic health. In addition, it posits that redlining is likely a key contributor to the ever-widening disparities in stroke outcomes even as the national incidence of stroke in the US is declining.

“While further research is needed, these results suggest that there may be residual effects of HRS [Historical Redlining Scores] on community stroke risk in certain New York City communities that are additive to classic SDOH defined by the Healthy People Framework,” the authors wrote.

“Similar to residual effects on community stroke risk stemming from a legacy of slavery in the southeastern US, redlining may be yet another example of historical structural racism with enduring effects on community-level cardiovascular health and specifically stroke prevalence, disproportionately affecting racial and ethnic minority communities,” they concluded.

The study included authors from Montefiore Medical Center, Columbia University Irving Medical Center, and the University of California, San Francisco and was led by Bruce Ovbiagele, MD, MSc, FAAN, professor of neurology and associate dean at UCSF and chief of staff at the San Francisco Veterans Affairs Health Care System.

“Redlining is part of the whole system of historical and structural racism that has led to all kinds of disadvantages and maldistribution of resources that affect risk of stroke and cardiovascular disease in Black and other populations that have historically been disadvantaged,” said Mitchell S. Elkind, MD, FAAN, professor of neurology and epidemiology at Columbia University Irving Medical Center and chief clinical science officer for the American Heart Association, where he also serves as senior staff science leader for all association initiatives related to stroke and brain health.

Color-Coded Redlining

During the 1930s, in the aftermath of the Great Depression, the federal Home Owners’ Loan Corp. (HOLC) was established with the goal of stabilizing the nation’s mortgage lending system and helping homeowners who were in foreclosure. Among other things, the HOLC was charged with appraising real estate risk levels of every metropolitan area in the country. It used local real estate developers and appraisers in over 200 cities to assign grades to residential neighborhoods, indicating where it was “safe” to insure mortgages.

These grades turned into color-coded maps:

• Green for the “best” neighborhoods—upper- or middle-class white neighborhoods that were “ethnically homogeneous.”
• Blue for “still desirable” neighborhoods composed of mostly White, native US-born populations.
• Yellow for “declining” neighborhoods, typically communities of first- or second-generation European immigrants.
• Red for “hazardous” neighborhoods, so characterized because of their “infiltration” of Black or “undesirable immigrant populations.” For example, HOLC assessors described one neighborhood in Minneapolis as “once a very substantial and desirable area” in decline because of the “gradual infiltration of negroes and Asiatics.”

Because many banks refused to underwrite mortgages in redlined areas, this made it difficult, if not impossible, for people in those neighborhoods to become homeowners. These discriminatory policies further disincentivized investment in these communities, producing a decades-long spiral of negative SDOH that have persisted long after the Fair Housing Act of 1968 outlawed this kind of neighborhood classification. Many neighborhoods that were labeled “Yellow” or “Red” in the 1930s remain marginalized and underserved today, often with few basic health care services, job opportunities, safe places to play and exercise, and transportation options.

A ‘Methodologically Sound’ Approach

“It is difficult to assess the link between structural and historical racism and present-day health and adverse stroke outcomes in a methodologically sound way, but these authors took an outstanding approach,” said Anjail Sharrief, MD, director of stroke prevention at UTHealth Houston Institute of Stroke and Cerebrovascular Disease.

“Even though this was a retrospective and ecological study, it still was very thoughtful in the way the authors accounted for SDOH and other important risk factors in the model, and they still found an independent association between redlining score and stroke risk.”

“It’s not just cardiovascular risk factors, it’s not just social determinants of health, it’s not just multigenerational trauma and allostatic load from historical redlining—it’s the interplay between all of these variables,” said Olajide A. Williams, MD, professor and chief of staff of the department of neurology at the Columbia University Vagelos College of Physicians and Surgeons in New York. “The effect these variables have on stroke risk always seems to be greater than the sum of the parts.”

For a long time, research into stroke risk focused on “traditional” risk factors, such as those used in the Framingham study, including age, blood pressure, diabetes, smoking, cardiovascular disease, and atrial fibrillation.

“I think this study tells us that we really need to start re-imagining the risk factor landscape and interrogating risk factors that we haven’t traditionally measured,” said Dr. Williams, whose research focuses on stroke disparities.

“The work that has been done in structural racism has unveiled the need to appreciate the relationship between stroke risk and these environmental stressors, both those of the present day and those that have lingered from legalized discrimination.”

Other studies, some national and some focused on specific cities, have reached similar conclusions about the relationship between redlining and stroke/stroke risk factors:

A study published in the Journal of the American College of Cardiology in 2022 found statistically significant increases in the prevalence of stroke as well as coronary artery disease and chronic kidney disease across more than 11,000 HOLC-graded census tracts, as the grades moved from A to D.

In the Multi-Ethnic Study of Atherosclerosis (MESA), which involves participants from Baltimore City and County, MD; Chicago; Forsyth County, NC; Los Angeles County, CA; New York City; and St. Paul, MN, investigators found that Black adults who lived in historically redlined areas had a 0.82 lower cardiovascular health score compared with those residing in grade A (best) neighborhoods.

A study published by the National Community Reinvestment Coalition in fall 2020, involving more than 12,000 census tracts nationwide, found statistically significant associations between greater redlining and stroke as well as chronic conditions such as asthma, chronic obstructive pulmonary disease, diabetes, hypertension, high high cholesterol, kidney disease, and obesity. It also found that, on average, life expectancy is lower by 3.6 years in redlined communities when compared to the communities that existed at the same time but had higher HOLC grades.

“Redlining segregated marginalized populations so severely that they didn’t have the ability to attain income, housing, social standing, safe neighborhoods, [and] schooling for their children,” said Dawn O. Kleindorfer, MD, FAAN, chair and Robert W. Brear Professor of Neurology at the University of Michigan, who studies the relationship between stroke and poverty. “It’s clear that this perpetuated a cycle over the years that had dramatic negative effects on the health of millions of people.”

The new study’s findings also debunk notions of race as an inherent “biological” risk factor for stroke. After fully adjusting for relevant risk factors, SDOH, and HRS, it found that a higher community prevalence of Black race and/or Hispanic ethnicity was negatively associated with neighborhood stroke prevalence.

“This strongly suggests that the disparities in stroke among Black and Hispanic populations are not biological but are driven by a combination of SDOH and risk factors,” said Dr. Kleindorfer. “The findings underscore the importance of awareness among neurologists around patients’ social circumstances and how those impact their health.”

“We know it’s not race, it’s the racism—but then what is the racism doing?” Dr. Sharrief asked. “How is it affecting people physiologically, biologically, and behaviorally to increase the cardiovascular risk? The idea of toxic stress, allostatic load, and generational effects that can be passed down is fascinating as a hypothesis for how race affects cerebrovascular health.”

Dr. Ovbiagele posited an epigenetic explanation for at least some of the increased risk. “There is certainly a link between historical discrimination and contemporary deprivation. But there’s also another question: Is it possible that being historically deprived biologically changes you in a way that makes you and later generations more susceptible to stroke in the contemporaneous era, through epigenetic processes that alter the patterns of gene expression through gene-environment interaction?” he asked.

Imperatives for Action and Research

With the neurotoxic legacy of structural and systemic racism stamped so thoroughly into American neighborhoods and communities, what can be done to try to reverse its effects? “That’s a question I’m asked all the time,” said Dr. Kleindorfer. “I believe we need to do more community-based participatory research, engaging communities and focusing on the issues they identify. Also, since redlining has concentrated social determinants of health in very specific areas, we need to use those redlining scores as a method for targeting community-based intervention.”

“The primary way to improve the situation is to invest in those communities that have historically been redlined,” agreed Dr. Elkind. “Support the establishment of businesses; improve schools; build healthy, safe neighborhoods; and work on those environmental factors that increase stroke and cardiovascular risk. Interventions need to be at multiple levels, focused both on individuals who live in those communities with downstream risk factors like hypertension, obesity, diabetes, and smoking but also on the community and population-level problems that give rise to those risk factors. To have an impact on reversing that generations-long legacy of maldistribution of opportunities and resources, we have to redouble our efforts to make sure that there are good health care facilities and physicians in those communities, that those neighborhoods are safe, and that people can get exercise and healthy, nutritious food.”

As an example, he cited the American Heart Association’s Social Impact Fund, which has invested over $100 million in programs in historically marginalized communities.

“We are supporting food banks, efforts to clean up neighborhoods, and make grocery stores that sell healthy food available in those communities and provide social investment and support social entrepreneurship to people who are trying to build institutions that will strengthen those communities,” he said.

“We are also working with the White House to build a Food as Medicine research program that will demonstrate the importance of healthy food and nutrition to improving the health of people with diet-related diseases. The goal is to do clinical trials at scale that will show the benefit of healthy food prescription programs that government, state, or private insurers should cover as a preventive health benefit.”

Dr. Sharrief is a lead investigator for VIRTUAL, a large clinical trial of a video-based intervention to reduce treatment and outcome disparities in adults living with stroke; the primary outcome is blood pressure control overall, while the secondary outcome is disparities in blood pressure control.

“The intervention involves team-based care for patients in the first six months after stroke, with a social worker, a pharmacist, and a nurse practitioner or physician,” she explained.

The team focuses on remote blood pressure monitoring with rapid notification as well as SDOH interventions around food and housing insecurity, insurance status, and other environmental and psychosocial factors. It also will collect data from all study participants about their experiences of discrimination and racism in the health care setting and everyday life, and how that may impact their long-term outcomes.

“We want to set them up for success and address all the factors that may affect their getting blood pressure under control,” she said. “A few interventions have been shown to improve blood pressure control, but none to date have been shown to narrow the disparities in control between racial and ethnic groups.”

Dr. Ovbiagele would also like to see research and translational initiatives focused on the epigenetics of stroke risk in marginalized communities. Environmental exposures (such as SDOH) can influence gene expression through epigenetic mechanisms, independent of the underlying DNA sequence.

“We know that epigenetic risk can be passed down through generations,” he said. “For an average 18-year-old Black man living in Harlem, in addition to the social determinants of health that affect him, he may have also inherited epigenetic markers from ancestors living in that area and started out somewhat behind even before taking those social factors into account.”

Dr. Williams agreed. “We have to look at the impact of structural racism across multiple levels. There are the physical effects, in terms of the diseases that result, like diabetes and hypertension,” he said. “Then there are the psychosocial drivers of these physical, biological diseases, including social determinants of health, but also the allostatic load associated with psychosocial distress.

“Then at the next level is epigenetics. We know that they can be passed down from one generation to the next: we’ve seen it with DNA methylation studies. Studies like this one force us to understand that the transmission of disease risk across multiple generations is not just a psychological and socioeconomic phenomenon but an epigenetic one. Of course, the adverse conditions in many of these communities haven’t changed that much since the days of legal redlining, but something else is also being transmitted from the days of Jim Crow to the present day that has made redlined populations carry risk forward from generation to generation.”

Dr. Ovbiagele thinks it may be possible to identify people who have been epigenetically impacted by historical discrimination such as redlining. “That would be the next step for us: to see if we can compare people who live in these areas that have been structurally impacted by racism, whether it be redlining or slavery, with people who contemporaneously live in areas not impacted and see if we can identify epigenetic markers,” he said.

“We know that unlike with DNA itself, we can modify the epigenome; epigenetic changes are dynamic and reversible. Several studies have identified how nutrition can reduce unfavorable epigenetics when it comes to cardiovascular disease, for example, by favorably impacting DNA methylation. Similarly, our ultimate goal would be to develop targeted nutritional, pharmacological, and other interventions designed to reduce the risk of first stroke and recurrent stroke in these populations.”

Understanding the epigenetic changes that may result from structural and systemic racism such as historical redlining will require much further research, Dr. Sharrief said.

“Once we understand what those changes are, then we need to assess how modifiable they are and the best way to modify them,” she said. “Is it a public health intervention, or are we looking at interventions that target communities or individuals? We have learned so much within just the past few years about toxic stress and allostatic load and their role in cerebrovascular disease. It’s a great time to work together and explore and understand more so that we can better understand how we address these factors.”