Fig. 3
Unweighted analysis of the relationship between age and gender-related differences in the annual decline in lung function (FEV1%) pred/year according to smoking. The squares/dotted line represents never smokers, the triangles/dashed line represents former smokers, and the diamonds/solid line represents current smokers. Recreated with permission from BioMed Central publisher and was first published by Gan et al. [64]