Table 2. Risk stratification scheme.

APOE ε2 carriers are assigned to the high or the low risk strata according to APOE genotype. Risk is assessed for all other subjects according to TOMM40 genotype. APOE ε2/2, APOE ε2/3 and VL/VL subjects are considered to be at low risk. Certain genotypes are considered high risk in the context of the targeted age range for the delay-of-onset clinical trial. Subjects with any of three 523 genotypes, S/L, S/S, and S/VL will be placed in the high risk category if he or she enters the trial at or older than the age indicated. 523 genotype frequencies are from the Cache County Study of Memory cohort (n=2,042)⁶⁸. APOE genotype frequencies are for Caucasian controls from Farrer et al. (n=6,262)⁴³.

523 or APOE genotype	Genotype frequency	Risk for the Study
For APOE ε2 carriers
APOE ε2/2	1%	All low risk
APOE ε2/3	13%	All low risk
APOE ε2/4	3%	All high risk
For non-APOE ε2 carriers
523 L/L	2%	All high risk
523 L/VL	13%	All high risk
523 S/L	14%	≥74 is high risk
523 S/S	17%	≥77 is high risk
523 S/VL	36%	≥76 is high risk
523 VL/VL	18%	All low risk