Type 2 diabetes, prostate cancer, multiple sclerosis — out of the nearly 200 reports 23andMe currently offers covering common and complex diseases, there are at least a few you have heard of. This familiarity is part of the reason why the Disease Risk reports are one of 23andMe’s most talked-about features. But looking at the genetics of a disease — and connecting that information to individuals — is a whole new way of thinking for most people. In this post, I’ll run through the basic nuts and bolts of a 23andMe Disease Risk report.
Each 4-star, or Established Research Disease Risk report contains information about the disease and its biology (located in the “How It Works” tab at the top of the page under the title of the report) and about established associations between genetic variants and disease risk (located in the “Technical Report” tab). The highlight of each report, however, is the individualized estimate of your risk for the condition. This estimate is based on your genetics, information about specific genetic variants that has been scientifically vetted, and publicly available statistics on how common the disease is. You’ll find this risk estimate in the section called the “Odds Calculator” under “Your Genetic Data”:
The example above shows that my risk of developing Type 2 Diabetes over my lifetime (estimated at 79 years) is 26.3%, based on my genetics and information applicable to people with Asian ancestry. The lifetime risk for the average Asian person is 20%, so I am at slightly increased risk based on genetics.
So what can I do with my risk information? Two sections underneath the Odds Calculator are relevant here. One, “Genes vs. Environment”, gives a rough idea of the relative influence of genetic and non-genetic factors for a condition or trait. Type 2 Diabetes, for example, is influenced strongly by non-genetic or environmental factors. So even if your results indicate a relatively higher risk for Type 2 Diabetes based on genetics, there are many environmental factors that influence your risk, and measures one can take to lower that risk. Some of these are listed immediately below “Genes vs. Environment” in the “What You Can Do” section.
The remainder of the report provides more detailed information about individual genetic variants used in the report to calculate a person’s risk. Below “What You Can Do” is a chart called “Marker Effects” (see picture below) showing the relative impact of each genetic variant on risk in the applicable ethnicity.
Mousing over each bar will display the location of that variant in the genome and your genotype — the two DNA letters you received from mom and dad — for that variant, as well as its effect.
For instance, my genotype at the second SNP, called rs1801282 and located in the PPARG gene, is CC. This genotype is associated with the highest odds out of all the genotypes for this SNP in East Asians — but that odds is only 1.04 times higher than average (because most East Asians have the CC genotype). The chart also tells me that most of my individual SNP risks are close to average, but my genotype at one SNP, rs7903146 in the TCF7L2 gene, contributes the most to my overall 1.32 times higher risk for type 2 diabetes. That’s why the red bar is tallest for that SNP.
For more information about each SNP, I can click on the “Technical Report” tab near the top of the page. The Technical Report lists each SNP used in the risk calculations with adjusted odds ratios for for each applicable ethnicity. (If you are sharing genomes with people at the Extended Level, you will also see their results here next to yours.) And for those who just can’t get enough, lists of scientific references used to justify each SNP’s inclusion in the report are provided for further reading.
Keep in mind…
When viewing a Disease Risk report, make sure to take everything in context. An elevated genetic risk is not necessarily cause for concern and a decreased or typical risk is not a reason to adopt unhealthy behavior. Both genetics and non-genetic factors influence our health and risks for diseases and science doesn’t yet know all of these factors or the exact effect of each one in every population. This is true even if we consider only the genetic factors. The handful of genetic variants used to calculate your risk for each Established Research report are only those variants that currently have strong evidence for being risk factors, and often, each variant only contributes a small amount to your risk. 23andMe will update the reports and your risk estimates as our knowledge improves, but they will necessarily remain works in progress.
As such, each genetic risk estimate represents only an approximation of the contribution of your genetics to your risk for disease, based on currently available knowledge. This information can still be very useful — the genetic variants included in the report on Venous Thromboembolism (current customers click here), a clotting disorder, have strong effects on one’s risk and knowledge of that risk could potentially be lifesaving. And simple healthy living goes a long way!
As with all of 23andMe’s Health reports, you are encouraged to contact your personal physician, a genetic counselor, or other medical professional if you are concerned or have questions about your results. 23andMe has partnered with Informed Medical Decisions, Inc., which provides independent genetic counseling services for 23andMe customers.
Current customers can learn more helpful tips and answers to common questions in our FAQ. In the next post, I discuss the reports available under Carrier Status for Inherited Conditions, which are especially relevant for those planning a family.