APOE and early-onset autosomal dominant Alzheimer disease: When we considered the APOE ɛ4 haplotype, we found that the prevalence of symptomatic Alzheimer’s disease was different across groups at age 40–45 years (Fig. 3A, Supplementary Table 4, P = 0.05), with the greatest prevalence in female ɛ4 carriers (44.4% versus 11.5% for female non-carriers, 9.5% for male non-carriers and 25% for male ɛ4 carriers).