Why Diversity Matters in Clinical Trials and Research

Medically Reviewed by Hansa D. Bhargava, MD on October 08, 2020
6 min read

Editor's Note: This article is part of a series in partnership with the All of Us Research Program, which collects and studies health data to help scientists identify health trends. More than 80% of participants are from groups that have been historically underrepresented in research.


You may know already that the medicines you take are tested first to see how well they work -- and how safe they are -- in studies called clinical trials. But you might be surprised to learn that the participants in these clinical trials aren't racially or ethnically diverse. And that lack of diversity can make a difference in how well we understand the effectiveness of medicines in different groups of Americans.

Though African-American people make up more than 13% of the U.S. population, they are only 5% of clinical trial participants.

More than 18% of Americans are Hispanic or Latino, but they make up only 1% of people in clinical trials.

Asian-American people are 6% of the population, but less than 2% of those taking part in studies.

Diversity matters in clinical trials. When researchers include a wide group of people, they can be more confident that the results apply to everyone who will one day take those medicines. How well a drug works, its chance of causing side effects, and the type of side effects you get can differ by ethnic group.

"The impact of not having a broad, wide range of people that participate in our clinical trials is we can not necessarily say that it will work equally well in all of those groups," says Lorna H. McNeill, PhD, MPH, associate professor and chair of the department of health disparities research at the University of Texas MD Anderson Cancer Center.

The Revitalization Act of 1993 says clinical trials funded by the National Institutes of Health (NIH) need to include minorities. Yet today, studies still have a lack of diversity.

"African Americans, Latinos, and other minority groups believe that research is important. They want to participate in research. But unfortunately, far too few of them are ever asked," says Stephen B. Thomas, PhD, professor of health policy and management, and director of the Maryland Center for Health Equity.

Issues that stand in the way of diversity in clinical trials include:

Lack of access. To join a clinical trial, you need access to the health care system and need to know that a study is available to you, McNeill says. You also need to meet the medical qualifications for the study and agree to join.

Many trials are performed at academic hospitals where people must have health insurance to get care. Black, Hispanic, and Native American people are less likely to have health insurance coverage than white people.

Even when people in minority communities do have a research hospital nearby where they can get treatment, they may not qualify for studies. Many trials exclude people with conditions like diabetes, high blood pressure, and kidney disease because they might affect the results. These diseases are more common in minority groups, who may automatically be left out, McNeill says.

Lack of information. Minority groups are less aware that they qualify to participate in studies. They may rely on their doctors or other health care providers to tell them, which doesn't always happen.

Even when African American people have access to research studies, they receive less information and education about them, McNeill says.

Lack of trust. Popular movies like Miss Evers' Boys about the Tuskegee Syphilis Study, and books such as The Immortal Life of Henrietta Lacks, describe unethical actions against African American people in clinical trials. The Tuskegee Syphilis Study investigated 600 Black men for 40 years without ever telling them the purpose of the research or giving them any treatments.

Henrietta Lacks was being treated for cervical cancer at The Johns Hopkins Hospital in Baltimore in 1951 when doctors took her cancer cells without her consent. Scientists all over the world have used her cells in research. Lacks' cells became the foundation of the multibillion-dollar biotechnology industry, but neither she nor her family ever received any compensation or acknowledgement.

McNeill says these stories don't stop every African American person from participating in clinical trials, but they do make them more cautious and skeptical about it. Although the U.S. has made its research policies more ethical since the time of Tuskegee and Henrietta Lacks, not everyone is aware of those improvements.

DNA collected during clinical trials is especially concerning to many African American people, who worry that their genetic material might later be used against them in a criminal investigation. "In many minority communities, the way they know about DNA is through crime shows," Thomas says. "There's a lot of criminal justice use of DNA, and we aren't able to clearly disentangle it from our medical use of DNA."

Lack of benefit. People in minority communities may feel that they aren't reaping benefits from their contributions to medical research. Tuskegee and Henrietta Lacks are two examples. The Havasupai Tribe is another.

In 2003, a member of this Arizona tribe sued researchers at Arizona State University after she discovered that DNA samples she'd donated for a research project on type 2 diabetes were being used for other genetic studies without her consent.

All of these cases are examples of people who participated in studies without knowing the truth and who didn't gain anything from the research. African American and Hispanic people continue to have higher rates of chronic diseases like cancer, diabetes, and high blood pressure than white people. "We've been poked and prodded. You've drawn our blood. And we're still sick. So what's going on with your research if the benefits of that science doesn't come to us?" Thomas says.

Lack of resources. It takes time and money to take part in a clinical trial. Not everyone can afford to take time off from work, travel to a center, and in some cases, pay for part of the care they receive. Research finds that people with annual household incomes below $50,000 are 27% less likely to join a clinical trial. The average household income for African American people is around $40,000.

"You might have a trial that's available to you, but if there are significant financial barriers, transportation barriers … you will decline participation because you can't adhere to the protocol that's presented to you," McNeill says.

In 2019, the FDA issued guidance to the sponsors of clinical trials to encourage them to include more minorities. It recommended that study sponsors widen the enrollment requirements to make more people eligible to participate.

The FDA also encouraged researchers to pay for study-related expenses like transportation, child care, and hotel stays. And it suggested that researchers hold studies in community-based medical centers and clinics, not just at academic centers that may be far from where people live.

Another way clinical trials can increase diversity is outreach to Black and Hispanic communities through places like churches, community events, barbershops, and beauty salons.

"We need to work with the people who already have trust in these communities, and many of them don't have MDs and PhDs behind their names. Some of them are local barbers and ministers," Thomas says. During COVID-19, he says outreach can be done virtually with tools like Zoom.

During outreach efforts, researchers can explain what a clinical trial is, what guidelines are in place to protect people who participate, and how the research will benefit them.

Once people agree to participate and enter research centers, there needs to be "in-reach," McNeill says -- clinical trial navigators who work with minorities to promote awareness and education. The coordinators who explain the study and serve as the main contact person should develop a rapport with participants and be sensitive to their concerns.

McNeill says research teams also need to hire more minority employees. Studies show that people respond better to medical professionals who look like them. "Not every single person, but somebody on that team needs to represent the racial-ethnic group of that patient," she says.

One organization making efforts to increase diversity in research is the All of Us Research Program. More than 80% of program participants are from communities underrepresented in biomedical research and more than 50% are from racial and ethnic minority groups.