Checking for Alzheimer's risk with 23andMe

Gene ExpressionBy Razib KhanApr 15, 2011 8:21 PM


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Dr. Daniel MacArthur at Genomes Unzipped:

23andMe announced yesterday that it will now be releasing information on Alzheimer’s disease risk markers in the APOE gene to customers who purchased their recently upgraded v3 test. The APOE markers are famously associated with a major increase in risk for late-onset Alzheimer’s, with individuals carrying two copies of the ε4 version of the gene being around 15 times more likely than average to develop the disease. Customers who have been tested on the v3 platform will be able to able to access their APOE status after “unlocking” it; customers on earlier versions of the test will need to upgrade to get access. You can see screenshots of the unlocking and results pages here.

I don't put much weight on 23andMe's disease risk estimates since I have a relatively large pedigree, and my four grandparents all made it at least to age 75 (one made it to 100, and two to 80+), so I have some sense of my odds of late onset diseases. But, I will admit I was still a little anxious when "unlocking" my results for this locus. This is a classic "tail risk" event which hooks into all the cognitive biases which we as humans come preloaded with. I will probably die of cancer or heart disease, but not due to a mutation of large effect which exhibits Mendelian inheritance patterns.* But I still fear that possibility! Well, I don't have the at-risk genotype. As someone who doesn't focus too strongly on medical genetics I was surprised that Alzheimer's is 60-80% heritable. This actually makes me someone less worried about this disease for myself, as across my extended pedigree this disease doesn't seem to crop up very often (my grandparents experienced rapid mental degeneration all within the last year of their deaths, it wasn't slow and gradual). Of course this is balanced by the recurrent issues with circulatory problems and such within my family. But I take proactive efforts to mitigate the environmental component of risk elevation, as well as the gene x environment interactions. In sum, there's no long term point in being ignorant. Though I will concede depending on your own psychology there may be a short to medium term benefit to not knowing your long term risks. * In fact, I don't have much of a history of cancer in my family. So it will probably be heart disease. This is what killed all four of my grandparents, though my maternal grandfather did make it to 95 before being diagnosed with the illness.

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