APOE and Alzheimer disease: Genome-wide association studies and meta-analysis (GWAS/MA) for AD have recently identified an R47H (rs75932628) loss of function TREM2 variant as a significant risk factor for AD, conveying an increase for AD with an odds ratio of 1.3-8.8-fold (p = 0.008), an effect comparable to that of the e4 allele of the 299 amino acid APOE lipid transporter (Gonzalez Murcia et al., 2013; Guerreiro et al., 2013; Neumann and Daly, 2013; Zhao et al., 2013).