It’s well established that at the DNA level, humans are about 99.9% identical. But the slight genetic differences that account for the remaining 0.1% can have significant consequences when it comes to genetic research.
In genome-wide association (GWA) studies, scientists look at hundreds of thousands of single nucleotide polymorphisms (SNPs) to find which ones occur more often in people with a trait or condition as compared to those without it. In the case of a disease, SNPs that differ significantly between the two groups can give scientists guidance in understanding its cause, developing treatments or determining whether a person with a certain genetic profile is likely to be affected. Unfortunately, associations between SNPs and a trait or condition often apply only to people of a particular ethnic background. This may be due to genetic differences between populations, or to environmental differences such as culture or geographic location.
And most of the large GWA studies are conducted in only one ethnic group: Northern Europeans. This means there are limits on how much benefit people from other groups are getting out of this exciting type of research.
After the jump, learn about some of the reasons that groups other than those with European ancestry have so far been left behind in the race to understand the genome:
1. Geography: Many of the large GWA studies have been carried out in Europe. The population there isn’t as diverse as it is in the United States, so there’s not a lot of opportunity to study people with African or Asian ancestry. Japan and China have fairly strong research communities, but so far they have not produced many large GWA studies.
2. Disease Prevalence: Many of the conditions that have been studied so far by GWA studies in the United States are more prevalent in Caucasians. It takes a lot of patients to do a robust GWA study, so it has been easier to study Caucasians first. (For example, Caucasian Americans are twice as likely to develop multiple sclerosis as African Americans)
3. Access: Health care disparities and proximity to research centers are not evenly distributed across ethnic groups. If researchers don’t have patients from a particular ethnic group to enroll in a study, that group can’t be represented.
It’s up to funding agencies like the National Institutes of Health to provide the incentives that will encourage researchers to carry out studies in groups that have so far been largely left out of GWA studies.
At 23andMe our goal is to give everyone, regardless of their ethnic background, the most information we can from their genome. But we also strive to provide our customers with only the very best information that has been rigorously reviewed by the scientific community. That means we can only report data in the Gene Journal (now called Health and Traits) for ethnic groups in which the associations have been validated.
Fortunately, this situation is likely to be temporary. Just a few years ago, there were no GWA studies of any ethnic group. With the passage of time, more research covering a greater proportion of the world’s population will be completed, and 23andMe will be able to report the results of these studies..