TGFB1 and chronic obstructive pulmonary disease: COPD patients also had significantly higher levels of TGF-β (284.60 ± 60.50 pg/mL) compared to smokers (160.00 ± 41.80 pg/mL) and non-smokers (92.00 ± 25.00 pg/mL) (p < 0.001 and p < 0.05, respectively).