Wednesday, April 11, 2012

Behavior + environment + epigenetics > genetics

A clever study by Bert Vogelstein & team of the impact of genetics on health outcomes was released last week. The study found that generally two people with the same genome (i.e. twins) were not significantly more likely than average to suffer from diseases with a genetic explanation. (n= 53,000 x 24 diseases.)

For some reason, the study's conclusion was trumpeted as revelatory, but I think this is overblown - we have long known that genetics does not dictate general health outcomes, but rather describes a general and remote tendency. We've also known that your "regular" genome does not equate to your "diseased" genome.

We've known for ~50 years that behavior and environment can have a tremendous impact on health outcomes (if you're a heavy smoker or work in a coal mine, your probability of lung cancer skyrockets regardless of your genome), and we're beginning to understand how other 'codes' such as the ribosome code and also epigenetics 'controls' DNA (though we're still far, far away from completing that understanding), so it shouldn't surprise that genetics is only a part of the health equation. If anything, the study above confirms once and for all that genetics - while part of the equation - isn't a majority explainer or even a plurality of the explanation. (Except for genetic disorders (like Tay-Sachs disease.) This isn't examined by the study.)

What I'm taking away from the Vogelstein study is that many of the public policy/privacy fears related to genomics are overblown - there are legitimate reasons to control access to your DNA - but in most cases, your insurance company learning that you have a gene that increases your likelihood of colon cancer by 10%, is less important than the insurance company knowing that you work at the Springfield nuclear plant.

Another good point here by Eric Topol: our current genetic understanding is based on a few dozen whole genome studies. It might be wise to wait until the 'n' = 1,000,000 or more profiles.

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