Genotyping, imputation, and quality control for the COGA sample are summarized in the Supplementary materials and described in further detail in Johnson et al. (2023). APOE haplotypes were derived using two SNPs (rs429358 and rs7412), from which the number of ε4 alleles were coded (0–2) and treated as a linear variable. There were 244 APOEε4 carriers (28.14%) in the analytic sample.
