We identified a rare SNP that was associated with FEV1 extremes in heavy smokers only, after adjusting for pack-years of smoking (p=1·16 × 10−8; table 2). This intergenic SNP on chromosome 12 (chr12:114743533, MAF=0·13%) also showed weak evidence of association with smoking behaviour (p=6·12 × 10−3; appendix pp 60–62). We noted evidence for change in expression levels with increasing fetal lung age (p=0·04) for one or more probes after adjustment for multiple testing for the nearby gene TBX5 (appendix pp 58–59).
