Illustration of a man and a woman carrying a large blue vaccine bottle between them as they walk along the tops of other bottles
USC experts are using data and findings from their research to press for action on disparities in health and well-being. (Illustration/Klaus Vedfelt/Getty Images)

He survived the Vietnam War and came home alive, unlike so many others his age.

Four decades later, the veteran was living on the streets of Los Angeles — and he was HIV-positive. He had been kicked out of his home when the property manager found out about his methamphetamine use. Homeless for more than nine months, he struggled to control his HIV. His anti-viral medications kept getting lost, stolen or confiscated by police officers and sanitation workers. He struggled to find food to eat and bathrooms to relieve himself. And his meth use continued.

USC health researcher Ricky Bluthenthal thinks of the man often — and of his downward spiral to street life. He also considers the health risks the veteran’s HIV poses to others and how they could’ve been avoided. Whether through unprotected sex or drug use, the chances the man would spread the virus to others were “quite high,” says Bluthenthal, associate dean of social justice at the Keck School of Medicine of USC. And it happened because of the stigma surrounding drug use.

We’ve created a system that really immiserates a particular subpopulation of people. And then when we go to help them, we often don’t even try very hard.

Ricky Bluthenthal

This raises crucial questions about how we structure society, he says: If people become homeless, do they have a say in how they live their lives? If they use drugs, do they lose the right to housing and health care? If their needs and desires are at odds with the system trying to serve them, whose fault is it when their lifestyle leads to disease and dysfunction on our streets?

“We’ve created a system that really immiserates a particular subpopulation of people,” says Bluthenthal, professor in the Division of Population and Public Health Sciences. “And then when we go to help them, we often don’t even try very hard.”

With racial and socioeconomic inequality comes health inequality — but USC researchers and experts are shining light on this issue. For Bluthenthal, that means examining the complex ways drug addiction, homelessness and HIV infection are linked and searching for solutions. Other USC researchers bring expertise in psychology, economics, communication, sociology and biomedical engineering to bear on the study of health disparities. They tackle varied challenges, from vaccine hesitancy to personal fitness to the wealth gap. But they share a common goal: creating a more equitable society.

Why Gay Black Men Face Health Disparities in HIV Risk, and How to Help

1 in 99 Americans are likely to contract HIV. For Black men who have sex with men, that figure drops to 1 in 2.

Nationally, the rate of new HIV infections is plateauing, if not declining. But that’s not the case among young Black gay and bisexual men. According to 2016 data from the Centers for Disease Control and Prevention, 1 in 99 Americans are likely to contract HIV, the virus that leads to AIDS. For gay white men, the risk is significantly higher: 1 in 11. For Black men who have sex with men, though, the numbers are startling: an estimated 1 in 2 will be diagnosed with HIV.

Lindsay Young wants to know why — and what can be done to reduce transmission in this vulnerable population.

Young is an assistant professor of communication at the USC Annenberg School for Communication and Journalism who completed her postdoctoral studies at the Chicago Center for HIV Elimination. Working extensively with the Black community in Chicago, Young and other researchers found that the area’s young Black gay and bisexual men tended to report fewer risky behaviors, fewer partners and more preventive behaviors than their white counterparts, yet their HIV rates are much higher.

When the researchers dug deeper, they found the answer in the men’s environment. They were more likely to lack access to health care. They faced more stigma in their community around having sex with men, so they shied away from seeking help and tended to go undiagnosed for longer periods. And the community itself was small and insular, making it easier for the virus to travel from person to person.

In response to these conditions, Young’s team went into the community and identified highly connected and influential people who agreed to be trained in talking about HIV prevention with their peers. They learned how to persuade friends to use pre-exposure prophylaxis, a daily medication that is highly effective at preventing HIV.

The researchers then checked people who called a local information line about the medication against lists of friends provided by the study participants. Young and her team confirmed that people who called the info line were more likely to be connected to study participants who had undergone peer training compared with study participants who had not yet been trained.

One man in his late 20s who went through the training had grown up in South and West Chicago and was born with HIV. When the researchers met him, he had only recently started identifying publicly as bisexual. As he participated in the study, he grew increasingly comfortable in his own identity and began to understand the importance of helping others feel the same way.

“If we achieve nothing else in these types of interventions,” Young says, “making people feel more empowered and comfortable in their own skin ­— and increasing their desire to share that experience with others — is quite important.”

How Genetics and Family Factors Combine to Create Health Disparities

In a sense, life can be seen as starting with two lotteries, says researcher Titus Galama. “One is the genetic lottery,” he says. “The other lottery is your family. You cannot choose your family or your genetic makeup.” Someone born with a “lucky” genetic draw in a wealthy household is more likely to live a longer life and receive more and better education.

“What I’m interested in is the implications for our understanding as a society of the meaning of equality of opportunity,” Galama says. “What does meritocracy mean when families and genetic makeup are such important factors?”

He studies the nexus of economics and genetics as a senior economist with the Center for Economic and Social Research at the USC Dornsife College of Letters, Arts and Sciences. He also directs the Center for the Study of Health Inequality. In his research, he tries to understand how early-life conditions — like nutrition, a mother’s education and household resources during a child’s first few years — can influence outcomes later in life. This area of research is called gene-by-environment interplay, and it’s at the cutting edge of a field called social-science genetics.

As people get older, the disparities in health between rich and poor widen. Workers from lower socioeconomic groups tend to work in more physically demanding, and perhaps more dangerous, jobs than workers with higher socioeconomic status. “If you look at doctors, they live much longer on average, while construction workers are literally doing back-breaking work,” Galama says. “Basically, if you don’t have much wealth or education, you have to rely more on your physical health, whereas wealthy people have the luxury to protect their health, because they can afford it. And being in good health helps people be more productive.”

By age 60, 7% to 8% of people earning high incomes report being in fair to poor health. That figure rises to 45% among people earning low incomes.

In later adulthood, the disparities among people from different socioeconomic groups can be vast. By age 60, Galama says, 7% to 8% of high-income individuals report being in fair to poor health, compared with about 45% of low-income individuals. By finding out what causes these disparities, Galama and other social science geneticists hope to start building critical bridges to improve health and well-being for all.

In one real-world example, Galama and his colleagues studied a basic income program in Colombia that provided extra money to poor families — on the condition that their children go to school and visit the doctor. Three years into the program, they found it led to more wealth, better jobs and more happiness for participating families. Financially supporting people, particularly those at the margins of society, and encouraging their children to get an education and health care has the potential to lift communities out of poverty.

Wearable Tech Helps USC Scientists Study Factors Behind Health Disparities

Activity trackers like an Apple Watch or Fitbit can help people stay healthy. Not only do they measure exercise but they also collect useful data on heart rate, sleep and circadian rhythm. Not everyone has access to these devices, however, which can leave some vulnerable people in the dark about their health.

Ritika Chaturvedi wants to find out more about those people, so the research scientist provided Fitbit trackers to 1,200 study participants, most with low-income and minority backgrounds. The idea is to see how they go about their daily lives in real time. She conducts the work through the USC Schaeffer Center for Health Policy and Economics, in partnership with USC’s Understanding America study.

Most people answer questions about their health when they visit their doctor, she says. “But doctors only see individuals maybe once a year, or once every two years, when something is wrong or they come in for a physical. You don’t really have a sense of how people behave over time.”

Fitbits, on the other hand, track steps, sleep and heart rate, day in and day out. The study’s participants — Blacks, Native Americans and people from households where Spanish is the primary language — wear the wrist devices for a year. The data collected are available to them as well as the USC researchers.

The point of this entire experiment is to identify the barriers to healthy behavior so we can develop interventions, all measured through something that’s very objective.

Ritika Chaturvedi

Participants also fill out a survey about what researchers call “social determinants of health”: racism, discrimination, poor access to health care, food insecurity, economic instability, educational issues and so on. By combining survey results and tracking data, the researchers hope to understand the factors that keep people from staying healthy and then come up with ways to counter them.

For example, in a neighborhood with a high crime rate, Fitbit data may confirm what participants say in their survey: They feel it is unsafe to walk or exercise outside. But what if many in the neighborhood go to church? Maybe a local organization or government agency could provide churches with treadmills and a plan that incentivizes community exercise.

Says Chaturvedi: “The point of this entire experiment is to identify the barriers to healthy behavior so we can develop interventions, all measured through something that’s very objective.”

USC Research Reveals Why Some People Don’t Want COVID-19 Vaccines

The same Understanding America study at USC is providing invaluable information on another area of health disparities: COVID-19 vaccines. With colleagues in USC’s Center for Economic and Social Research, researcher Wändi Bruine de Bruin started tracking Americans’ reactions to the coronavirus pandemic starting on March 10, 2020. More than a year later, the team has found disparities by age, race and political affiliation as people across the country reacted to the threat of this highly infectious, sometimes lethal virus.

Study researchers now survey a panel of about 6,000 people in the U.S. every two weeks. Since April 2020, they’ve asked respondents if they would be willing to get vaccinated. “There have been differences in vaccine hesitancy in racial and ethnic groups, but they are getting smaller,” says Bruine de Bruin, Provost Professor of Public Policy, Psychology and Behavioral Science at the USC Price School of Public Policy.

A bigger predictor of vaccine hesitancy than race, she says, is education. The lower their education level, the less inclined they are to get vaccinated. The percentage of adults without a college degree who say they are unlikely to get vaccinated is about the same among Black and white people — 32% and 35%, respectively. But the percentage of adults without a college degree who are unsure about getting vaccinated is much higher among Blacks (23%) than whites (11%).

Another intriguing finding from the study: Older adults are more likely to believe they could die from the virus than younger adults, but they perceive less risk of getting COVID-19, having to quarantine or running out of money. Additionally, an American’s likelihood of wearing a mask and observing social distancing guidelines could be predicted by whether they identify as a Democrat (more likely) or a Republican (less likely).

People look to others around them to inform their behaviors.

Wändi Bruine de Bruin

Long before COVID-19, Bruine de Bruin had studied why people do or don’t get vaccines. “One insight from that work,” she says, “is that people look to others around them to inform their behaviors.” That led her to advocate for the “vaccine selfie” — when newly vaccinated people take a picture of themselves at the vaccine site to share on social media.

“Then their friends and family will realize that this person has gotten vaccinated,” she says. “That should increase the likelihood that they will also get vaccinated.”

Bruine de Bruin saw this dynamic play out in her own life when she posted a vaccine selfie. A friend reached out after seeing the picture, wanting to know why she got vaccinated and how she could be sure it was safe. Bruine de Bruin explained her thinking and in doing so, persuaded her friend. “She decided to get vaccinated,” she says, “because she trusted my opinion.”

Where We Live Can Harm Our Health — and Our Kids

It’s clear that many aspects of our personal lives, like our racial and ethnic background, class status or the neighborhood where we live, can affect our well-being. To untangle those factors and their links to health disparities, Brian Finch, a research professor of sociology at USC Dornsife and director of the Southern California Population Research Center, crunches big data.

One study Finch published this year explored how living in neighborhoods with gangs affects birth outcomes like being born early or underweight, even among residents who aren’t gang members. When gangs take over a neighborhood, the violence can scare businesses away, he says, creating fewer economic opportunities. Neighbors stop talking to neighbors because it feels unsafe to be outside. Shootings put whole blocks on edge.

If you’re not allowed to use social spaces because they are controlled by gangs or if you’ve got to keep your eyes out constantly for gang activity, it’s just not a healthy environment.

Brian Finch

“It’s ambient stress,” he says. “You don’t have to experience it yourself. It’s there in your neighborhood. If you’re not allowed to use social spaces because they are controlled by gangs or if you’ve got to keep your eyes out constantly for gang activity, it’s just not a healthy environment.”

And we now know, Finch adds, that the health of a woman at the time she becomes pregnant and the conditions during her pregnancy can affect the health of her baby.

Scouring Los Angeles County and city data, they found that accounting for the presence of gangs “explained a number of disparities between non-Hispanic Black infants and non-Hispanic white infants,” he says. And tragically, mothers-to-be could only do so much to mitigate the damage. “All your behaviors during pregnancy, whether you attend prenatal care and that kind of thing — even controlling for those factors didn’t completely reduce the disparities.”

Illustration of a woman and a man carrying a blue bar between them as they climb other blue bars arranged like a graph

USC researchers tackle health disparities with the goal of creating a more equitable society. (Illustration/Klaus Vedfelt/Getty Images)

USC Experts Press for More Action on Health Disparities

For years, Finch has studied health disparities in specific populations, hoping his work would lead to solutions for underserved communities mired in poverty. Instead, he’s watched these disparities spread to great swaths of American society.

We’ve been under a longstanding, long-term onslaught of income inequality. It seems there’s a big bifurcation going on in this country right now.

Brian Finch

“We’ve been under a longstanding, long-term onslaught of income inequality,” he says. “It seems there’s a big bifurcation going on in this country right now.”

Addiction. HIV. Early childhood health and well-being. Barriers to fitness. Vaccination rates. Life expectancy. USC experts say the evidence is there: Health disparities in the United States are real and in many cases, profound. Even more concerning, the problems aren’t getting any better. Finch fears they may be getting worse.

Twenty-five years ago, as a graduate student, Finch wrote papers documenting health disparities and cited research that came before him. Today, his grad students cite the papers he and his colleagues wrote in the 1990s on the same inequities. He wonders when, as a nation, we will finally decide we have enough evidence to act.

“We’ve spent so many decades documenting disparities,” he says. “We’ve got to begin to turn the corner on that. If you do believe, like I do, that the social determinants of health are driving disparities, then it all just seems kind of intractable and almost unfixable — unless we are willing to deal with the major social problems of our time.”

The issue is gaining attention, as evidenced by President Joe Biden’s recent appointment of a health equity czar to address health disparities. But until major progress is made, Bluthenthal knows that people like the veteran he met on the streets of Los Angeles will continue to struggle. His research shows that homelessness alone puts individuals at higher risk of poor health outcomes. That effect is magnified for people from marginalized and underserved populations.

In a study published in May, Bluthenthal and colleagues found that certain groups of drug users were less likely than others to have access to naloxone, a drug that can prevent death from opioid overdose. Whites were more likely to have access to the drug than Blacks or Latinos, as were housed people relative to those without housing.

Bluthenthal’s goal for his research is to connect such data to the larger social inequities that lead to intractable addiction problems, both at the individual level and for communities. “The other thing is beginning to advocate, through telling stories, for a more systemic, more structural response to the problem of substance use disorder.”

“We have to get better at creating the evidence that connects structural conditions to institutional problems,” he says. “We have to begin asking new questions.”

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