To examine the effect of smoking on the causal pathway between the SNPs and the traits of interest, an adjustment for smoking was applied. The subgroups of ‘ever-smokers’ and ‘never-smokers’ were analyzed separately, and the stratum-specific estimated effects were combined within each individual study using inverse variance weights before meta-analyzing over studies. Additional adjustments were undertaken by adjusting for pack-years among the ever-smokers with these data available, and repeating the analyses.
