Sunday, February 27, 2011

My 23andMe Results: The Importance of Non-Genetic Risk Factors

NOTEGetting Advice About Genetic Testing

When I first saw my 23andMe results, I was very glad to see that each genetic association also had a heritability value.  For example, the disease description for Type 1 Diabetes indicates that 72-88% of the disease is determined by genetics whereas the sample description for Type 2 Diabetes indicates that 26% of the disease is determined by genetics (meaning that 74% is determined by environmental factors).  In other words, there is a lot more that can be done to prevent the onset of Type 2 Diabetes than Type 1 Diabetes.

I was also glad to see a “What You Can Do” section describing what actions high risk individuals could potentially take to prevent or manage their disease.

Although these two steps may represent the best way to currently convey this information for most associations, I think it would really help if non-genetic factors could directly be incorporated into risk calculations.

For example, I noticed that one of my Promethease results indicated that a long history of high blood sugar would increase my risk for CAD from 1.7x to 7x (for SNP rs1333049).  If 23andMe could incorporate information about my medical history directly into my risk calculations, then I think that could make the predictions much more powerful.

In addition to providing more precise risk assessments, I think incorporating non-genetic information could also actively help individuals manage their health.  For example, if I knew that losing 30 pounds would cut my risk of developing a particular type of cardiovascular disease by 50% based upon a personalized quantitative model, then I would probably be more inclined to lose that weight than if I simply knew that eating right and exercising was generally a good idea.

That said, I think there are some fundamental changes that may need to take place before such an idea could be implemented (assuming science has progressed to the point where we could provide such models for most diseases).  First, I think users need a more dynamic way to record their medical information in 23andMe.  By this I mean that users need to be able to update their medical information rather than fill out surveys at one point after they create their account.  For example, I responded that I didn’t have any serious illnesses (like cancer, cardiovascular disease, etc.), but I’m sure my answers to those questions will change over the course of my life.

In order to integrate both genetic and environmental risk factors into risk calculations, it may also be helpful to think about other ways to present genetic testing results (which I discuss in greater detail in my third post on predictive models).


  1. The issue with 23andMe's surveys is that they aren't done (as far as I can tell,) to assist in determining risk factors but to help them make "discoveries."

    As long as they have no interest in using any of the data in that way, this model, while ideal, is unlikely.

  2. Thanks for the comment.

    Perhaps my blog post was unclear. Although it would certainly be cool if 23andMe could also identify non-genetic risk factors (similar to predictions made by PatientsLikeMe,, I was talking about the slightly different task of integrating genetic and non-genetic risk factors into a risk assesment. For example, it would be OK if such models only incorporated well-established non-genetic risk factors into an overall risk assessment.

    In general, I should probably also emphasize that I would call this a "cool idea" that may be very difficult to implement at this time. @dgmacarthur provides a useful reference to about gene-environment interactions in the final paragraph of a Geomes Unzipped post I was in no way trying to imply that 23andMe failed to offer this service due to a lack of effort.


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