The three lung function traits we studied are correlated. The overall and genetic correlations were: 0.88 and 0.87 between FEV1 and FVC; 0.46 vs 0.35 between FEV1 and FEV1/FVC and; 0.038 and -0.17 between FVC and FEV1/FVC (transformed traits, as studied in UK Biobank and SpiroMeta15, respectively). One might expect variants showing strongest association with FEV1 and FEV1/FVC to be of greatest relevance for COPD and genetic correlations of -0.76 and -0.9 have been reported between COPD and FEV1 and FEV1/FVC, respectively42. We show, however, that variants associated with one of these traits also tend to be associated with one of the other two lung function traits studied (for example, all but 2 signals for FVC are also associated (P<0.05) with FEV1, Supplementary Table 4). Although classification of COPD in UK Biobank was based on pre-bronchodilator spirometry, we have previously shown that this leads to minimal misclassification of moderate-severe (GOLD 2-4) COPD43. The effect size estimates for COPD associations could be influenced by differences in case ascertainment between the follow-up studies. Motivated by avoidance of potential winner’s curse bias for
