We estimated the additive array heritability of each individual's long-term average age and BMI-adjusted BP residuals using GEAR v0.7.730. Array heritability estimates may be more sensitive to artifacts than GWAS results57, so we restricted our analysis to the largest group of individuals, non-Hispanic whites, that were run with the same reagent kit and type of microarray (n=73,133)46. We used only autosomal data, a common practice in array heritability estimation, and also LD-filtered our data so no two pairwise SNPs had r2>0.8 with a standard greedy algorithm in plink v1.0758. This resulted in 547,922 genotyped SNPs, and 3,796,606 imputed SNPs restricted to rinfo2>0.8. Because of population stratification, we used PC-Relate29 to estimate kinship coefficients rather than the standard GCTA estimates31 which assume a homogeneous population; we also compared the results to those obtained using the standard GCTA kinship estimates with PC adjustment. We used GEAR rather than GCTA to estimate heritability since the PC-Relate kinship matrix estimate was not positive definite; this can be explained by the fact that the matrix entries are computed based on different allele frequencies, i.e., those
