June 19, 2019

The vast majority of genomic data scientists have collected focuses on people of European descent, overlooking minority populations. As genetic-based precision medicine grows, this data gap means minorities may lack access to medical care that could reduce growing chronic disease disparities among racial and ethnic groups.

Precision medicine is an approach that allows doctors to select treatments that are most likely to be effective in protecting a patient’s health or treating their disease, based on an understanding of the patient’s individual genes, environment and lifestyle. This approach allows doctors and researchers to better predict which treatments and prevention strategies will work for which people, but it can’t be used effectively without access to accurate information for that particular individual or group.

A team of researchers from institutions across the country, including the University of North Carolina at Chapel Hill, analyzed phenotypes of nearly 50,000 non-European individuals, identifying 65 new associations and replicating 1,400 associations between genes and diseases, highlighting the need for equitable inclusion of diverse populations in genetic research.

Dr. Misa Graff

Dr. Misa Graff

Dr. Kari North

Dr. Kari North

Kari North, PhD, a professor in the Department of Epidemiology at the UNC Gillings School for Global Public Health, and Misa Graff, PhD, assistant professor in same department, are co-authors on the paper “Genetic Diversity Improves Our Understanding of Complex Trait Architecture,” which was published June 19 in Nature. North was the senior co-leader and oversaw the research and Graff was a co-junior lead.

“This is an extremely important public health issue,” Graff said. “We need to work hard to make sure that the populations most burdened by disease are not overlooked by genomic studies, because we cannot afford for disease disparities to get worse. Understanding the genes in these populations is key to targeting prevention and designing drugs that can better address their illnesses and improve quality of life.”

Overall, minority populations are affected disproportionately by chronic diseases such as hypertension, diabetes, cardiovascular disease and cancer. According to statistics from the United States Department of Health and Human Services’ Office of Minority Health, African-Americans are 80% more likely than non-Hispanic white adults to have been diagnosed with diabetes and 30% more likely to die from heart disease.

According to the Centers for Disease Control and Prevention’s National Center for Health Statistics, Hispanics (47%) and non-Hispanic African-Americans (46.8%) had the highest age-adjusted prevalence of obesity, followed by non-Hispanic whites (37.9%) and non-Hispanic Asians (12.7%).

The study, known as Population Architecture using Genomics and Epidemiology (PAGE), was founded by the National Human Genome Institute and the National Institute on Minority Health and Health Disparities to research the correlation between genetics and disease in ethnically diverse individuals in the U.S. The study was led by a large research team made up of researchers from many academic and medical research institutions across the country, including the Icahn School of Medicine at Mount Sinai, the Fred Hutchinson Cancer Research Center in Seattle and the University of Southern California.

In analyzing the genetic codes of these diverse populations and comparing them to codes from people of European descent, researchers identified 65 new genetic associations — previously undiscovered positions along a chromosome where related genetic variants are located — that have not been found previously in European populations, but have the potential to be transferable to other groups that share components of genetic lineage, such as African ancestry, which can be found in African-Americans, Hispanics and Latinos.

For instance, the association between lower HbA1c levels – which often is used as a marker for glucose control — and the gene for sickle cell anemia had been well reported in African-American populations. The team’s work demonstrates the importance of this variant in some Hispanic/Latino populations as well. When Hispanic/Latino individuals carry this sickle cell variant, as they commonly do in populations of African ancestry, the estimated values of HbA1c levels could be erroneously lower, leading an individual to incorrectly think that they are free of Type 2 diabetes or that their glucose is well under control.

“It is important that we no longer make assumptions based on what someone looks like or their perceived race — which is an inappropriate biological construct — and project what they might be at risk for or whether their disease is under good control,” said North.

Another key finding is a risk variant associated with a higher number of cigarettes smoked per day. This risk variant is virtually absent in most populations, but found at a significantly higher rate among populations with Native Hawaiian or Pacific Islander ancestry. The finding can now help identify other new biological traits that may not have been discovered.

Among the Native Hawaiian or Pacific Islander population, the variant was found in 17.2% of study participants. If the study hadn’t included this population, however, this association would not have been noticed.

As urban areas are experiencing population growth and genes are mixing more and more, including diverse groups in research becomes even more important. It also is important to acknowledge the risk of misdiagnosing diseases if diverse populations remain unstudied.

“An important step in genetic medicine is determining how often a genetic variant occurs in healthy people. If a variant is common in the wider population, it is unlikely to be harmful, but in most of our databases that ‘wider population’ is comprised mostly of European ancestry,” said North. “Unless we increase our efforts to study diverse populations, we are going to continue to make these mistakes.”

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