Checking for Alzheimer's risk with 23andMe

By Razib Khan | April 15, 2011 11:21 am

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.


Comments (7)

  1. They don’t yet seem to be offering results for Huntington’s Disease. This would seem to be technically straightforward, at least for initial detection. Is this the result of political pressure against making such information available outside of a controlled context?

  2. The real “risk” for Alzheimer’s is complex and weakly understood (and quite possibly changing). 23andMe is only dealing with probabilities and associations (not true individual risk) — many will gain a false sense of relief from their results, and of course others may have an excessively heightened sense of alarm from their results. The cautionary verbiage that 23andMe offers is fine (and necessary), but, people being people, will still tend to read too much into their individual results.

  3. Re: Dr. Daniel MacArthur
    The APOE gene results in early onset Alzheimer’s. Dr. Suzanne DeLaMonte at the Rhode Island Hospital, Brown University, said on the Dr Oz Show last Friday that nitrosamine is a serious toxin to brain neurons and that very low density lipoproteins which APOE stops its ability to metabolize it. What produces very low density lipoproteins? One source is fructose metabolism in the liver which was discussed in June 10, 2011 NY Times Magazine on work done at the San Francisco Medical Center by Dr. Lustig. About 30 percent of the metabolic products by the liver is very low density lipoproteins which can be determined by a blood test. Dr Oz thinks that genes are not the major cause but it is our diet. I agree with HFCS excess in our drinks and processed foods as being the major cause of obesity and the metabolic disorders such a diabetes 2 and heart disease. Search Vitamin D too.

  4. Ian

    Got my kit today, so I suppose I’ll find that out in the not-so-distant future. Pretty sure there’s nothing of the sort on my father’s side – counting him, there are four siblings over 75 in that family, and there were three nearly-double first cousins (shared three grandparents with my father) who made it past 80. Much less certain about things on my mother’s side…

  5. Zxcv

    Huntington’s Disease is caused by a short tandem repeat and cannot be genotyped by their chip.

  6. Thanks, Zxcv. I wasn’t aware that their testing method had that sort of limitation.


Discover's Newsletter

Sign up to get the latest science news delivered weekly right to your inbox!

Gene Expression

This blog is about evolution, genetics, genomics and their interstices. Please beware that comments are aggressively moderated. Uncivil or churlish comments will likely get you banned immediately, so make any contribution count!

About Razib Khan

I have degrees in biology and biochemistry, a passion for genetics, history, and philosophy, and shrimp is my favorite food. In relation to nationality I'm a American Northwesterner, in politics I'm a reactionary, and as for religion I have none (I'm an atheist). If you want to know more, see the links at


See More


RSS Razib’s Pinboard

Edifying books

Collapse bottom bar