We used the categorical SQ levels defined by Thorgeirsson et al.7. The SQ levels were 0 (1–10 cigarettes per day), 1, (11–20), 2 (21–30) and 3 (31 or more). Each increment represents an increase in SQ of 10 cigarettes per day. Most of the cohorts in our study have maximal CPD recorded on each sample but a few have collected average CPD (Supplementary Table 1). We examined the distributions of CPD across cohorts and found no large differences between those cohorts with average or maximal CPD. The mean and standard deviation of the CPD measurements in each cohort are given in Supplementary Table 1. The Ever/Never and Current/Non-current phenotypes used were those collected by the individual cohorts. Not all cohorts had all three phenotypes collected. Precise details of the phenotypes collected in each cohort are given in Supplementary Table 1. An assessment would typically be questionnaire-based, following a structure such as: Tick the option that best describes you:-I smoke now-I don’t smoke now. I have stopped for … years.-I have never smokedAbout how many cigarettes do you or did you smoke per day?Put the number of years you have smoked.
