Clinical characteristics of the subjects involved in the studies.

All values are represented as median values with ranges in parentheses. Ex –smokers = not smoking for at least one year. FEV1 % predicted = Forced Expiratory Volume in 1 second as percentage of predicted value; FVC = Forced Vital Capacity. Stage means severity of COPD according to GOLD criteria. Statistical significance determined by a kruskall-wallis ANOVA followed by Dunn's multiple comparisons test or a two-way student's t-test for unpaired observations. *p<0.05, **p<0.01, ***p<0.001 compared to Control group and #p<0.05 compared to individuals with COPD stage II.