Our final sample consisted of 37,463 participants, with an average age of 63.9 years (SD = 7.7). Of those, 13% had APOE ε2/ε3, 61% had APOE ε3/ε3, 24% had APOE ε3/ε4, and 2% had APOE ε4/ε4. Table 1 shows the study sample characteristics, including mean age with SD, as well as the number of participants in each age group, by APOE genotype. There was a significant difference in mean age and the distribution of age categories by APOE genotype (P < 0.001), reflecting a smaller proportion of older participants with ε3/ε4 and ε4/ε4 in our data (see Figure S2 in supporting information). This finding is consistent with previously reported differential survival based on APOE status. 28 Aside from BMI (P < 0.01), all other sociodemographic and lifestyle characteristics did not differ among APOE groups.
