Analyses of larger samples using Haploview (5), that expanded the samples of this study to a total of 245 EAs (minor allele frequencies for SNP-1: 0.30; SNP-2: 0.50; SNP-3: 0.36; SNP-4: 0.30) and 37 AAs (minor allele frequencies for SNP-1: 0.50; SNP-2:0.26; SNP-3: 0.16; SNP-4: 0.08), provided further evidence that the two SNPs have a high degree of linkage disequilibrium (LD) (Figure 2). ANCOVA did not detect significant differences in hippocampus volumes among the populations studied (p>0.6); since there are no differences in the phenotype in the different populations studied, population stratification is unlikely to be the cause of the observed differences. Whole brain gray matter analyses did not reveal any other regions with significant difference between the genotypes. There were no significant findings associated with the other two (flanking) SNPs (SNP-1 and SNP-4).
