As most effect sizes were below 1%, we set the power analysis parameters at R 2 = 0.001% to 1% as a range for the effect size and 2,000–400,000 as a range for the sample size. For an effect size of 0.001% even a sample size of 400,000 results in a power level of only 50%, whereas for an effect size of 1% a sample size of 8,000 suffices to achieve 80% power. In our study, the average observed effect size of the top SNP was R 2 = 0.11%, resulting in sufficient (>80%) power levels at sample sizes of at least N = 7,100. A visualization of power as a function of effect size and the SNP sample size are provided in Figure S1A,B.
