I've made a 23andMe parser that can report on this. Actually, it covers quite a lot of their health results:

https://github.com/cslarsen/dna-traits

The test for Alzheimers is here: https://github.com/cslarsen/dna-traits/blob/master/py-dnatra... (the algorithm used to be patented, by the way). By closely reading the algorithm, you can probably find out yourself, given that 23andMe still lets you browse your genome.

To see all health reports, run this file on the downloaded genome: https://github.com/cslarsen/dna-traits/blob/master/py-dnatra... (you have to compile the C++ code first)

Actually was playing with the idea of monetizing off this project, but the laws in my country prohibit me from doing so. In fact, just using the program I made is illegal unless its my own genome.