By contrast, plasma TGF-β levels weresignificantly higher in COPD patients than in healthy controls (0.018±0.0035vs 0.0073±0.0014 ng/mL, P=0.002; Figure 3B), in patients with GOLD III and IV vs GOLD Iand II disease (P<0.01; Table 2), and incurrent and ex-smokers than in never smokers (P<0.01 and P=0.012, respectively;Figure 3D). Here, TGFB1 is linked to chronic obstructive pulmonary disease.