The gold standard of modern genomics studies, the results of which guide thousands of investigations into the genetic roots of disease and development, are based almost exclusively on people of European ancestry. Unless that changes, most of humanity might miss out on the genomic revolution.

“Geneticists worldwide must investigate a much broader ensemble of populations, including racial and ethnic minorities,” write geneticists led by Carlos Bustamente of Stanford University in a July 14 Nature article. “If we do not, a biased picture will emerge of which variants are important, and genomic medicine will largely benefit a privileged few.”

In genome-wide association studies, known as GWAS, researchers compare the genomes of hundreds or thousands of people, looking for differences in DNA. It’s hoped that GWAS will explain what’s known as the missing heritability: Scientists have so far been able to explain biologically only a small fraction of disease risks known to be hereditary.

At first, researchers expected that “common variants,” shared by relatively large numbers of people, would account for that missing heritability. These proved not to matter much, with each common variant linking to miniscule fractions of disease risk. Now researchers are concentrating on rare variants: mutations shared by relatively few people, but with powerful effects.

Whereas common variants tend to be shared across racial and ethnic groups, rare variants seem to be group-specific. Findings from one population, such as variants linked to diabetes in Europeans, often don’t appear in others. The most thorough analysis ever performed of ethnicity and genetic variation, led by Bustamente and published July 5 in Proceedings of the National Academy of Sciences, underscored this phenomenon.

A comparison of between-group overlap in rare and common variants. Carlos Bustamente/Nature

Yet as of now, genome-wide association studies focus overwhelmingly on Europeans and their descendants.

A 2009 review by Duke University geneticist David Goldstein found that 96 percent of all GWAS genomes came from people of European ancestry. Into that remaining 4 percent is crammed every other racial and ethnic group, though in absolute numbers they represent the vast majority — roughly 80 percent and growing — of humanity.

“Additionally, studies of other populations have generally included smaller sample sizes than those of participants of European ancestry,” wrote Goldstein in 2009. “Moreover, only a few studies have even included, let alone focused on, subjects with African ancestry.”

The National Institutes of Health mandated diversity in federally funded genetics studies in 1985, but the requirement hasn’t been followed. To an extent that’s understandable, as most genomics is conducted in the United States and western Europe, where most people have European ancestors. They’re a conveniently accessible study group. But with genome sequencing costs plummeting, there’s no excuse for remaining exclusive, write Bustamente and colleagues.

“It is tempting to focus on populations that are motivated, organized, medically compliant and otherwise easy to study,” they write. “We risk perpetuating the health disparities that plague the medical system. Those most in need must not be the last to receive the benefits of genetic research.”

Image: Christian Rieger/Flickr

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Citation: “Genomics for the world.” By Carlos D. Bustamante, Esteban González Burchard and Francisco M. De La Vega. Nature, Vol. 475 No. 7354, July 14, 2011.