Understanding How the Intersectionality of Race and Socioeconomic Status Predicts and Promotes Health Disparities

Socioeconomic status is one of the most important determinants of how resources are allocated in society, Williams said. “In virtually every country in the world where we have data, it is a predictor of variations in health.” But in the United States, he noted, low socioeconomic status does not exist in a vacuum—it is related to race and ethnicity. Williams cited data on median household income from the U.S. Census Bureau in 2017, which showed that for every dollar a White household receives, Asian American households receive $1.23, Hispanic households receive 73 cents, and households who identify as Native American or Black receive only 59 cents. “What is stunning about the 59-cent figure for [Black households] is that is identical to the Black-White gap in income in 1978,” Williams said. These income figures, he noted, underestimate the gap in economic status, because, compared to White communities, people of color have markedly less wealth and thus far fewer economic reserves at their disposal.

But socioeconomic differences alone do not fully account for the racial and ethnic disparities in health, Williams said. Race intersects with socioeconomic status at every level of education and income, such that Black communities have worse health than White communities at every level of income and education. To understand these striking racial inequities, Williams particularly pointed to how races have been physically separated by enforced residence in certain areas (known as residential segregation), with the intention of protecting White households from Black households and fostered racial inequality (Williams and Collins, 2001). Racial segregation may no longer be legal, but its effects persist, and it impacts access to resources and thus, health risks and access. “Think of segregation like a burglar at midnight,” he said. “It slips into the community, awakens no one, but once it shows up valuables disappear, like quality schools and safe playgrounds, and access to good jobs and a healthy environment and safe housing and access to high quality transportation and high-quality medical care. Research in the United States indicates that all of these wonderful resources vary by your zip code, vary by your neighborhood, vary by where you live.” Rigorous empirical analyses of national data in the U.S. reveal that access to opportunity at the neighborhood level, created by segregation, accounts for racial disparities in income and education (Chetty et al., 2020; Cutler and Glaeser, 1997).

Segregation also creates an inequitable distribution of health care services and those living in predominately Black neighborhoods have less access to health care than neighborhoods that are exclusively White and that the health care they have access to is generally of lower quality (White et al., 2012).

Segregated neighborhoods where the residents are predominately underrepresented minorities are also linked to higher levels of exposure to life stressors in multiple domains of life (Sternthal et al., 2011), Williams said. In addition, people who have been historically disenfranchised are also subject to interpersonal discrimination. Research on one aspect of discrimination, indignities in routine interpersonal encounters, called everyday discrimination, reveals that such exposure is linked to numerous negative health outcomes including cognitive impairment, poor sleep, and cardiovascular events (Barnes et al., 2012; Johnson et al., 2021; Lewis et al., 2006; Williams et al., 1997).

The consequences of this lifelong segregation, stress, and discrimination is “weathering,” Williams said. Biological weathering, sometimes called accelerated aging, indicates that chronological age captures not just age, but the degree of exposure to these repeated stressors over years and related physiological dysregulation (Geronimus et al., 2010; Sternthal et al., 2011). Future research, Williams said, could take into account these environmental stressors and their role in biological weathering. Achieving equity will require not just studies of distinct exposures and biology, he said, but also “interventions in the neighborhood conditions, the drivers of the inequities in the first place.”

Experts working in CNS disorders have only recently begun to take these environmental risk factors into account, said Bernadette Boden-Albala, the director and founding dean of the University of California, Irvine's future School of Population and Public Health. “Early studies were primarily done around CNS disorders in White populations, and really focused on biological risk factors,” she said, and the assumption was that relatively few contributors to conditions such as stroke were modifiable. But over the past 20 years, Boden-Albala continued, the focus has shifted to thinking about the impact of the social and structural environment (Figure 1), “everything from food availability to pollution to transportation, to structural barriers to community resources.”

FIGURE 1

The Determinants of Inequities in Neurological Disease, Health, & Well-Being Framework. This schematic shows the many complex influences that play a role in disparities in equity surrounding neurological health and well-being. Structural issues (more...)

Now, she said, scientists have identified the risks of particulate matter in the air, noise pollution, lack of access to green space, temperature, and even poor neighborhood cohesion for disorders such as Alzheimer's disease, epilepsy, and stroke.

One of the ways that stressors from the built environment can manifest is in sleep health, said Dayna Johnson, a sleep epidemiologist and assistant professor in the Department of Epidemiology at the Rollins School of Public Health at Emory University. Good sleep health is, on its own, “necessary for memory and learning, emotional regulation, immune and inflammatory function, metabolism, and cardiovascular regulation,” she said. Poor sleep is linked to a number of adverse health outcomes, she added, “including cognitive decline, dementia, cardiovascular risk factors such as stroke, as well as mortality.”

Poor sleep and undiagnosed sleep disorders are more common in racial and ethnic minority groups, she continued. “Different features of the physical environment, such as noise, as well as living in areas with a higher population density” can contribute to short sleep duration and poor sleep quality.

To reduce these inequities in health, Boden-Albala said, “clearly identifying and really addressing structural barriers is key.” Interventions might address issues such as the effects of historical redlining and inclusion in clinical trials and community engagement, she noted. These interventions could also be innovative, including community networks and health models, and multidisciplinary teams, she said.

Johnson said that she is working on one of those interventions, examining how weatherizing homes could improve sleep and cognitive function, and she mentioned another study which found that clearing and landscaping local environments resulted in reduced crime and an increased sense of safety, thus reducing structural barriers to improving health.

Examining Health Effects of the Built Environment Early in the Lifespan

Disparities in CNS disorders across the lifespan may have their roots earlier in development, said Daniel Hackman, associate professor at the University of Southern California's Suzanne Dworak-Peck School of Social Work. “This can be due to disparities that emerge in childhood and adolescence and persist,” he said, “or to early differences in psychosocial and biological development that may be part of the risk pathway to later emerging disparities.”

There are many opportunities for the environment to influence child and adolescent development, Hackman said. “In most developmental theories,” he explained, “children are thought to develop within a broader, dynamic, multi-level context in which individuals grow up nested in micro-level environments such as families and peer relationships that are themselves nested in higher level or meso-level contexts, such as physical environments, including pollution and toxin exposure, social environments, service environments.” Importantly, for children, these higher-level environments include schools, he explained.

Systematic divestment is the purposeful withdrawal of investment which can lead to a lack of improvement or infrastructure within a neighborhood or community.³ Neighborhood disadvantage related to the systemic divestment in communities Williams highlighted, are associated with worse mental health in adolescence, Hackman explains, “as well as biological indicators of stress or weathering.” But there is less research for CNS disorders, he said.

Hackman highlighted one study from his research team which used the Adolescent Brain Cognitive Development (ABCD) study,⁴ a longitudinal study of nearly 12,000 youth and their families that began at ages 9–11. His group has already shown that higher neighborhood disadvantage was associated with decreased working memory performance and a pervasive pattern of lower performance across tasks and neurocognitive domains, as well as lower cortical surface area (Hackman et al., 2021). “Neighborhoods appear to matter in a certain respect for brain development,” he said. “With the caveat that causal evidence is lacking thus far.” More research is clearly needed, he said, especially in the potential role for any CNS disparities in childhood and adulthood.

Under-resourced neighborhoods, which are often the product of structural racism, can have their effects on brain health throughout the lifespan via exposure to neurotoxins, said Micaela Martinez, the director of environmental health at WE ACT for Environmental Justice (WE ACT). For example, she said, lead exposure can come from old plumbing or paint used in homes built before 1978 as well as from modern toys imported from other countries. There is no safe level of lead, she noted, but there are both socioeconomic and racial disparities in childhood lead exposure. Citing the 2011 to 2016 National Health and Nutrition Examination Survey (NHANES), Martinez showed that Black children ages 1 to 5 have 1.35 times the blood levels of lead of White children.⁵

Lead isn't the only neurotoxin of interest, Martinez said; there is also mercury. Many skin-lightening products contain mercury, she explained, because it is a blocker of melanin. Using a product containing this neurotoxin is dangerous not only for the users, she said, but it can put everyone living with a user at risk “because mercury can vaporize and it is odorless and colorless.” In a survey that WE ACT conducted of 297 women and femme-identifying people of color living in upper Manhattan, Martinez said, “25 percent of all women surveyed used skin lightening products at some point in their life, and 57 percent of Asian American respondents used skin lighteners” (Edwards et al., 2023).

Not only does exposure to these products cause direct physical harm which is disproportionally experienced by communities of color, she said, but it also causes psychological and social harm “because these products are grounded in Eurocentric beauty standards and white supremacy.” The net result, Martinez continued, is that the burden of environmental racism—and its impacts on health—falls heaviest on communities of color.

Connecting Environmental Factors with Downstream Health Impacts

Manly said that most of the data showing disparities in CNS disorders are collected as clinical data and cannot directly show the impact of the environment. How then, Manly asked, can researchers understand the influence of environmental risks and the built environment as drivers of CNS disorders.

In response, Johnson said that scientists “aren't collecting the data necessary to answer that question.” To collect those data, she said, researchers need to measure structural racism and structural discrimination.

It is radical interventions that will address the fundamental causes of CNS diseases and disorders, Boden-Albala added. “I do not think that we have been brave enough yet to bring those kinds of interventions.”

Implementing Change in the Face of Public Backlash

Currently, 30–40 percent of the U.S. population rejects concepts such as structural racism and encourages these topics be excluded from research and discussion, highlighted a workshop participant. The participant wondered how researchers and activists can implement change in this type of environment.

In response, Martinez said that “we can't change everybody's mind to be onboard with understanding the legacy of white supremacy in this country, but what we can do is use the resources that are available and that are going to be more and more available in the next few years to try to tackle some of these issues.” She highlighted the Inflation Reduction Act, which includes funding for environmental justice initiatives.⁶ It is a tough situation, she said, but “we also have one of the greatest environmental justice opportunities that will come in our generation.”

Williams agreed that the situation is challenging and said that working with communication experts would be key to successfully helping people emotionally connect with stories from systematically disadvantaged communities. “We know that there is an empathy gap; [people feel more empathy for the suffering of someone of their own race than someone of a different race,] but there are narrative strategies that can be used to reduce the empathy gap,” he said.

Mitigating Neighborhood Disadvantages through Supportive Communities

During the panel discussion, Manly took a question from the audience inquiring of the panel whether there are any protective factors “like family structure, social support, community cohesion that might mitigate the negative effects of neighborhood disadvantage” on CNS disorders and disparities.

Hackman answered that while his own research has shown that systemically divested neighborhoods are associated with differences in brain development, there is other research which details the positive effects of supportive and warm parenting and social support (Brody et al., 2017, 2019; Rakesh et al., 2021; Whittle et al., 2017). He also emphasized that protective factors and opportunities can be found in environments such as schools. They are not only places for teaching and learning, he said, but also environments that promote social and emotional development across the board. Thinking at a higher level, there is also a role for policy to create protective factors through programming and interventional approaches which could lead to broader structural change, Hackman concluded.

There is evidence that social networks can be protective, Boden-Albala said. “Neighborhoods that are more cohesive are neighborhoods that have less stroke, for example.” Now, Boden-Albala added, her group is looking at whether family-supported management of hypertension risks could be more effective than an individual being solely responsible for managing his or her own health. Boden-Albala is also examining family support in Latino and Vietnamese communities in Southern California and looking for barriers to social network support in order to help inform policy changes by government agencies. Social networks could be a powerful factor in protecting community members from the inequities posed by their environments, Boden-Albala said. Incorporating positive factors such as social support, she suggested, could be just as important for reducing disparities in CNS diseases and disorders as decreasing environmental risks.

Understanding Biological Pathways Linking Early Environment and Later Health

People living in historically marginalized communities not only may have higher risks of neurotoxin exposure, as emphasized in the first session by Martinez, but they also are more likely to be exposed to early childhood adversities, which are powerfully linked to later health outcomes, said Katie McLaughlin, a professor of psychology at Harvard University. Trauma and adversities in childhood can lead to changes in brain development, she said, but many of those changes can actually help children adapt to the stress of their environment. Still, she continued, this short-term adaptation comes “at a long-term cost in terms of increasing risk for physical and mental health problems later on in life.”

Early-life adversity, McLaughlin said, also increases the biological weathering that Williams had spoken of. “The body literally ages more quickly in children who have experienced early life adversity,” McLaughlin said. This embedding of the environment in a child's body, she said, is a key mechanism that can contribute to health disparities.

But these consequences of early life adversity aren't inevitable, McLaughlin continued. She presented data from her lab from a survey of more than 11,000 U.S. children showing that health disparities were reduced by between one-third and one-half in states with generous social safety nets for low-income families (Weissman et al., 2023). This suggests, she said, that policy solutions can reduce the consequences of early childhood adversities “if we have the political will to make them happen.”

When Amezcua asked McLaughlin about the potential for interventions to reduce disparities in childhood, McLaughlin said that resilience could be found at multiple levels. At the family level, she said, social support can be a powerful protective force against the long-term biological consequences of early-life adversity. “In many cases this can be the presence of just a single adult who has invested emotionally in that child's well-being,” she explained.

At a more macro level, McLaughlin agreed with Hackman that supportive school environments could also protect against some of the negative effects of adversity. Both of these social contexts, she emphasized, can hurt or help. McLaughlin referred to her recent scholarly work showing that when children grow up in a context that is structurally stigmatizing toward an identity they hold, such as race or sexual orientation, that stigma can leave measurable impacts on the size of the brain's hippocampus and other brain developmental markers that are associated with CNS diseases and disorders (Hatzenbuehler et al., 2022).

On the other hand, McLaughlin said, in a social context that is supportive of a child's identity, which could be familial, school, or another context, “you see not only a reduction in risk, but that those contexts can actually protect you against these individual sources of stress and adversity.”

Highlighting the Burden of Alzheimer's Disease and Alzheimer's Disease-Related Dementias on Minority Communities

Since 1970, life expectancy among American Indian and Alaska Native communities has risen from 47.5 years to 71.8 years (Manson and Buchwald, 2021), said Spero Manson, Distinguished Professor of Public Health and Psychiatry, director of the Centers for American Indian and Alaska Native Health, and the Colorado Trust Chair in American Indian Health within the Colorado School of Public Health at the University of Colorado Denver's Anschutz Medical Center. Unfortunately, he said, this increase in life expectancy has had implications for the occurrence of Alzheimer's disease and Alzheimer's disease-related dementias (AD/ADRD) among this population. In the 1970s, American Indian and Alaska Native communities were generally unaware of AD/ADRD due to the reduced life expectancy of most Native communities, Manson said. “We have seen at least an eight- to tenfold increase in the prevalence of AD/ADRD” as life expectancy has increased.

A higher prevalence of AD/ADRD also exist in the Black and Latinx communities, said Monica Rivera Mindt, Professor of Psychology, Latinx Studies, and African and African American Studies at Fordham University, and a professor of neurology at the Icahn School of Medicine at Mount Sinai. Black and Latinx adults are up to twice as likely to develop AD/ADRD as White adults, she said, and they have higher risks at earlier ages and greater symptom severity. If current population estimates prevail, she said, Black and Latinx Americans will constitute 40 percent of families affected by AD/ADRD. “This is just simply unacceptable.”

Cultural factors account for some of the differences in AD/ADRD and in CNS disorders more broadly, Rivera Mindt added. Citing Manly's research, Rivera Mindt said that poor education, acculturation, and socioeconomic status are associated with higher risks for cognitive impairment and even dementia in some cases (Rentería et al., 2019). “Cultural heterogeneity is also an important factor,” she said. In her own work, she showed differences within subpopulations, finding that Puerto Rican adults have higher risks for cognitive impairment than Mexican American adults.

Finally, Rivera Mindt said that syndemics—the cooccurance of two or more diseases or disorders in a population—is an important issue to consider. “Syndemics is just a way of thinking about these different systems or spheres of influence and where they intersect,” she said. That may mean, she explained, that more complex interventions, working on multiple levels, would be needed.

Understanding the Impact of Traumatic Brain Injury and Spinal Cord Injury on American Indian and Alaska Native Communities

AD/ADRD are one of three major CNS disorders that are especially high among American Indian and Alaska Native communities, Manson said. Acute spinal cord injury rates are among the highest in the United States among American Indian and Alaska Native people, he said, “largely as a function of the environments in which many of us live.” Socioeconomic conditions, including lower seatbelt use, increased alcohol-use disorders, and neighborhoods with fewer pedestrian safeguards affect driving in American Indian and Alaska Native communities, Manson explained, leading to higher rates of motor vehicle accidents. “It is no accident,” he said, that American Indians experience motor vehicle accidents and spinal cord injuries at rates that are between four and eight times higher than the rates among non-Hispanic White counterparts in places like Arizona and New Mexico.

Finally, Manson said, the rate of traumatic brain injury (TBI) “among the military personnel and now our veteran population is substantially greater than any other subsegment.” Military personnel are, of course, exposed to the dangers of combat, he noted, but American Indian and Alaska Natives are also exposed to “high rates of interpersonal violence that lead to physical injury and often TBI.”

These populations experience higher rates of CNS disorders, but affordable and accessible care is “typically not available to Native people,” Manson said. To help reduce inequities in case, he continued, policy makers will have to pay attention to how care is structured and financed.

Promoting Resilience via Community for American Indians and Alaska Natives

Even as American Indian and Alaska Natives experience disproportionate diagnosis of CNS diseases and disorders, Manson said, community ties, such as those highlighted by Hackman, Boden-Albala, and Williams, can play an important role in resilience. “There are those wellsprings of resilience in Native communities that make a difference in terms of both risk and protection, and ultimately, coping with the consequences,” he said.

When Amezcua inquired about the factors that could sustain this resilience, Manson said that decreasing inequities in CNS disorders in American Indian and Alaska Natives could be driven by diversifying the scientific workforce and understanding that community-based participatory research “actually improves our science.” Incorporating community partners, he said, would help researchers bring in the communities' own experiences and models of their conditions. Community input, he explained, provides important constructs that scientists might attend to “both in terms of our science as well as preventive and clinical care.” This community-based participatory research, Manson added, improves science as well as “the nature of care that our people deserve.”

Reviewing Strategies for Increasing Equity and Inclusion in Clinical Trials

“Innovation [in] science and medicine is really only meaningful if it is accessible to all and applies to all,” said Jason Mendoza, the head of multiple sclerosis and immunology at U.S. Medical, at Biogen. However, he added, because of regulatory requirements and a need to isolate potential safety concerns for drugs under investigation, patients with comorbidities are often excluded from phase III clinical trials. Just as underserved patients are already experiencing inequities in access to care, he said, they also end up excluded from clinical trials. “African Americans comprise approximately 14 percent of the U.S. population but usually have less than 5 percent representation in clinical trials,” Mendoza said. “For Hispanics, who make up 18 percent of the US population, clinical trial participation is about 1 percent.”

The equitable inclusion of community partners is key at every step of the research process, “from study, question design, implementation, and even dissemination,” agreed Rivera Mindt. Black and Latinx populations are more likely to get AD/ADRD, but they remain underrepresented in research on these CNS disorders, she said, “which again is unacceptable.”

To promote equity and inclusion, Mendoza said, Biogen is now making efforts to better reflect national population demographics in its clinical trial recruitment. This not only increases equity, he said, but it increases confidence in the trials' results. As an example, Mendoza cited recent COVID vaccine trials run by several companies. “Those trials had enrollment targets for underrepresented populations, and the company has actually slowed down enrollment to ensure that communities of color were represented and made up about one-third of the total enrollment,” he said. Now, Biogen is doing the same for lupus clinical trials, he added.

Rivera Mindt said that in her own studies in Harlem she and her colleagues have worked to incorporate the community. As they scale up across the country, Rivera Mindt said, the result is not just equity, but is better research as well. The internal reliability of the studies gets better as researchers take into account sociocultural factors, she said, and the results are also more generalizable “by making them more inclusive and more representative as we move forward.”

It can be challenging, however, to recruit patients from underserved populations, in part due to recruitment methods, said Jon Strum, founder and host of the RealTalk MS podcast,⁷ which provides scientific education and outreach to those living with or caring for someone with multiple sclerosis (MS). Another challenge is fear, he said, some of which is from the many historical failures that have led to the death of clinical trial participants. But “some of that fear simply stems from a lack of reliable information,” he said. “It is the most fundamental fear, fear of the unknown.”

“It is difficult to motivate change without first creating understanding,” Strum said. He uses his podcast, he said, to combat fear with education and information. He also builds engagement with the MS community by encouraging them to contact him with their feedback. Once patients and caregivers have reliable knowledge, Strum explained, they feel more empowered to participate in clinical trials as they see fit. “It is basic communication, conversations in easy-to-understand language,” he said. “That is the not-so-secret sauce.”

When Amezcua asked Strum about increasing diversity in studies, Strum said some of the most effective methods he had found involved bringing in thought leaders from underserved communities. They “can speak directly to the barriers that they face every day,” he said, “and in many cases dispel some of the false information that is sometimes too closely held.” He recalled that after having conversations with those thought leaders on his podcast, clinical trial investigators would report an uptick in trial recruitment. Strum also emphasized the importance of partnering with patient advocacy groups which can extend the reach of a message.

Facing the Key Challenges to Implementing Culturally Based Interventions

Amezcua asked panelists to share some of the key challenges they faced implementing culturally based interventions. Rivera Mindt said that one of the key challenges for national work is that most of the work of a culturally based intervention takes place in a very local context. Those on the ground, she explained, need to know their local populations and tailor their response. “Each of us does not have to be an expert in all things, and we don't have to do everything all at once,” she said. “But we do need to know the populations that we are working with.”

Another challenge, Rivera Mindt said, is that there has been a rush toward diversity in studies, but not enough thought given to whether the people designing those studies have the right expertise. “Big projects, clinical trials, organizations need to take their time and make sure they have the appropriate expertise, regardless of a person's background, in order to do the best possible job with the populations they want to understand and serve,” she said.

Amezcua agreed and noted that this would require cultural humility and addressing researchers' implicit biases. Following a question from the audience, she asked the panel how genetic differences might be weighed against equity-related issues when studying health outcomes.

All outcomes are influenced by both genes and environment, replied McLaughlin, but only one of those is something that scientists, communities, and policy makers can directly influence. “Ultimately the DNA that we are born with is the DNA that we stay with,” she said. “So, the place where we have an opportunity to intervene is in those environmental factors.”

Epigenetics, Manson said, is also a place where scientists can learn more about the early life effects of environment that might have long-term impacts. “I think that's where the action will be, at the intersection of in person and environment,” he said.

Mendoza noted that there are genetic differences in risk factors for diseases such as MS or amyotrophic lateral sclerosis (ALS) and said that it is possible to keep an eye on both genetics and environment. “I think there's room for both in this area,” he said.

Rivera Mindt agreed that looking at genetics, environment, and epigenetics would be valuable. She also offered a word of caution, noting that race is a sociocultural construct and to be mindful of conflating race and genetics.

Encouraging Research on Resilience as Well as Environmental Change

As many researchers and community partners emphasized during the workshop, the disparities in CNS disorder prevalence and severity, as well as disparities in access to research and care, arise from a multitude of factors, including race, socioeconomic status, sexual and gender minority status, early-life adversity, and much more. As such, Williams said, research should consider approaches to disparities in CNS diseases and disorders from multiple angles. “We need research priorities to identify the resilience resources as well as the upstream mechanisms that play an important role,” he said, “and we need interventions to improve neighborhood conditions, the drivers of inequities in the first place.”