Linear regression of age, age2, sex, height and ancestry principal components was undertaken on FEV1 (milliliters) and FEV1/FVC (percentage). The residuals were transformed to ranks and subsequently to normally distributed z scores, and were then used as the phenotype for association testing under an additive genetic model using software specified in Supplementary Table 1. Appropriate tests for association in related individuals were applied where necessary, as described in the Supplementary Note.
