Mean plasma level of KL-6 was higher in the middle aged/elderly males with COPD when compared to non-smokers in the group (middle aged/elderly male non-smokers 292 ± 78 U/ml, middle aged/elderly males with COPD 556 ± 64 U/ml; p = 0.037) (Figure 1B). This evidence concerns the gene MUC1 and chronic obstructive pulmonary disease.