Power was calculated using the program Quanto (http://hydra.usc.edu/GxE/). Assuming a quantitative expression trait with mean 0 and SD 1, a sample size of 1,490 subjects, a type I error of 5.78×10−12 and an additive allele effect, the study had a 82% power to detect the effect of a SNP explaining 4% of gene expression.
