ACE and chronic obstructive pulmonary disease: COPD-chronic obstructive pulmonary disease, NLF-normal lung function controls, VBD-voluntary blood donor controls, p-p value, OR-odds ratio, CI-confidence interval, N-number of subjects, eNOS-endothelial nitric oxide synthase, ACE-angiotensine converting enzyme.<br>aadjusted for age, sex and smoking status, badjusted for age and sex.