UK Biobank participants were recruited from March 15, 2006, to July 7, 2010. Sample selection for the UK BiLEVE study started on Nov 22, 2012, and was completed on Dec 20, 2012. We initially selected 50 008 unique samples representing the extremes and middle of the percent predicted FEV1 distributions; this comprised 10 002 individuals with low percent predicted FEV1, 10 000 individuals with average percent predicted FEV1, and 5002 individuals with high percent predicted FEV1 from each of the heavy smoker and never smoker groups (figure 1). Within this dataset, 48 931 unrelated individuals passed quality control and were included in subsequent analyses.
