Main characteristics of the population at index event in relation to the three study groups.

Group A: patients with at least one severe exacerbation of chronic obstructive pulmonary disease (E-COPD)in the three-year pre-index period; Group B: patients with only moderate E-COPD in the three-year pre-index period; Group C patients without E-COPD in the three-year pre-index period.SD = standard deviation.' % of the whole population.'' COPD is not considered as a comorbidity.1p2 p