Every human on earth is unique our genes are different, we eat different things, we live in different places. As a result, medical treatments tend to work differently on different people. Depending on your genes, a drug might cure your sickness or it might cause a side effect that makes you sicker.

In the past, many of humanitys individual variations were invisible to us, but today, new technology offers us a way to peer into each persons genome, allowing doctors to personalize treatments for each patient. This approach, called precision medicine, has been a major focus of research and investment in the last few years.

But precision medicine only works if scientists have studied people who are similar to you. If your genes are rare or unusual compared to those researchers have examined in the past, you could end up getting the wrong treatment. Since the vast majority of genetics studies are done on people of European ancestry, members of other racial groups may lose out on the benefits of precision medicine entirely. Those same groups already often receive worse health care in the United States than people of European descent get, and personalized medical treatment could make the gap in care larger.

Precision medicine is based on the idea that genes can be linked to diseases. To study this, scientists assemble a group of people, some with a disease and some without, and identify their genetic differences. If particular differences are common among the people who have the disease and absent from the people without it, then scientists can infer that those genetic patterns might be involved in the disease.

But each person has their own catalogue of genetic characteristics. Some are common in people of certain ancestral backgrounds and rare in those from other backgrounds. If scientists exclusively study individuals of one ethnic group, they may not know how to refine their treatments for a person from a different group.

A 2009 analysis of the studies that can link a genetic variant to a disease or trait showed that fully 96 percent of participants were of European descent. In a 2016 commentary in the journal Nature, Alice Popejoy and Stephanie Fullerton, respectively a graduate student and a professor at the University of Washington, showed that these studies had grown more diverse and people of European ancestry now account for 81 percent of research subjects. Things are getting better, and its still pretty darn slow, Fullerton said in an interview. And of the progress that has been made, much of it is attributable not to an increase in diversity in U.S. research but to studies conducted in Asian countries, which involve local participants.

Disparities in biomedical research exacerbate an existing gap in U.S. health care. African-Americans and Latinos are less likely to have health insurance and more likely to suffer from chronic diseases. Even controlling for wealth differences between populations, African-Americans receive worse health care.

The science underlying precision medicine threatens to make these disparities worse because it could leave any genetic differences that primarily affect nonwhite groups unstudied. Some genetic differences are prevalent in one population and rare in another. A prominent example is a gene called APOL1. Differences in this gene are common in people whose ancestors are from sub-Saharan Africa but rare in those of other backgrounds. Some of these variations increase the risk of developing kidney disease more than sevenfold, but they also seem to confer protection against African sleeping sickness. Knowing a patients APOL1 genetic makeup might be useful for guiding kidney disease treatment, and APOL1 is likely one of many genes that must be studied within a nonwhite population.

Its possible to solve the problem of underrepresentation. The National Institutes of Health fund a number of large-scale genetic research projects in the United States, and scientists there consider this a major issue. We are aware of this situation, and work is being funded to rectify the situation, said Charles Rotimi, an investigator at NIH. He pointed to initiatives like Human Heredity and Health in Africa and the Population Architecture using Genomics and Epidemiology Consortium. These projects are developing more diverse study populations to address the underrepresentation of people of non-European ancestries, in some cases going to African countries to collect genetic data. In the United States, individual investigators can also apply for smaller-scale NIH grants to study particular diseases.

Even when scientists make a conscious effort to recruit a diverse study population, they can run into hurdles. For very good reason, minority populations can be more skeptical and concerned about being involved in biomedical research, said professor Danielle Dick of Virginia Commonwealth University, who studies how genetics contribute to a persons risk of substance abuse. The good reason Dick referred to is a long history of biomedical researchers mistreating people of color, including in the Tuskegee trials and through the forced sterilization of Puerto Ricans. Dicks team and others have tried to address issues of underrepresentation by visiting various hospitals to recruit Hispanic or African-American study participants, providing educational materials about genetics research, arranging to collect samples when patients may be off work, and taking other measures to encourage participation.

But the imbalance in samples is so severe, and the rush to develop precision medicine is so swift, that the problem may not be solved before treatments are developed, and as a result, those treatments will likely predominantly help people of European ancestry. The time horizon for a lot of therapies is typically in the 10- to 15-year range, Fullerton said. Could we solve it in that time frame? Possibly. But genetic differences may already be causing disparities in treatment results between groups. Some genetic variants that are common to certain racial or ethnic groups can affect a patients tolerance for drugs, for example, so knowing about a patients genetic code can guide a physicians prescription. Doctors are observing these phenomena in the clinic already, said Nishadi Rajapakse, an NIH administrator at the National Institute on Minority Health and Health Disparities.

Clinical differences in health care are only likely to become more severe as precision medicine advances. New drugs are already targeting certain genetic differences, although none that would function primarily in one ethnic group and not in others. In the long run, people of European ancestry could benefit from ever more specialized treatments while people of color are left behind.

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Medicine Is Getting More Precise For White People - FiveThirtyEight