APOE and Alzheimer disease: Overall, there is a tendency that protein levels are more likely increased (positive effect size, β) than decreased (negative effect size, β) in AD patients that carry the APOE ε4 allele (Fig. 1a,b) and those homozygous for APOE ε3 allele (Fig. 1c) but not for APOE ε2 patients (Fig. 1d).