Descriptions of APOE_RiskScore variable:

A risk score based on the apolipoprotein E (APOE) gene was calculated, with a
higher risk score indicating having a higher amount of genetic risk for Alzheimer’s
disease (Darst, et al. in review). APOE was coded by the e2/e3/e4 genotype formed
by rs7412 and rs429358. Risk due to APOE status was calculated according to the odds
ratio (OR) of the e2/e3/e4 genotype, as indicated in the meta-analysis of APOE
genotype frequencies in studies reported in AlzGene[1]. These ORs were based on studies of
Caucasian individuals and were calculated using the e2/e2 genotype as the reference
(e2/e2 OR=1) as follows: e2/e3 OR=1.38, e3/e3 OR=2.00, e2/e4 OR=4.45, e3/e4 OR=6.78,
e4/e4 OR=25.84.

Note that the 'APOE_RiskScore' reported here is the natural logarithm (ln) of
the OR.