These variants are actually unlinked. Plus, it doesn’t matter if the genetic factors are linked, providing you take this into accout when you calculate the odds ratios.

]]>However, one thing I don’t understand is that when calculating the combined odds ratio for the genetic factors you assume that the different risk variants are not correlated. Surely this can’t be correct?

Doesn’t genotype imputation work because the opposite is true? (i.e. variants in the genome are indeed correlated.)

]]>You might explain “over what period of time” and “what are my odds of dying with Alzheimer’s at 80 compared to dying without having ever gotten it?”

Two others points. I know I’ve seen several Navigenics reports and all of them have had an APOE-linked genotype reported. But I don’t subscribe and can’t remember which marker or chip.

Finally, you might explain risk over time. Adrienne Cupples and Lindsay Farrer did a lot of work to assemble some risk curves:

http://journals.lww.com/geneticsinmedicine/Abstract/2004/07000/Estimating_risk_curves_for_first_degree_relatives.4.aspx (Genetics in Medicine 2004)

You might explain “over what period of time” and “what are my odds of dying with Alzheimer’s at 80 compared to dying without having ever gotten it?”

]]>As a quick example, suppose you had a high risk factor with a frequency of 25% and an odds ratio of 2 between high and low risk. You mean risk is 0.75*1 + 0.25*2 = 1.25. So the low-risk factor has an odds ratio of 1/1.25 = 0.8, and the high-risk factor has 2/1.25 = 1.6.

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