Inhaled corticosteroids and pneumonia mortality in COPD patients

Extract

I thank P. Almagro and co-workers for their letter, which provides updated data regarding the association between inhaled corticosteroids (ICS) and pneumonia mortality in chronic obstructive pulmonary disease (COPD). It confirms the shortage of, and need for, rigorous studies on this question. My article, on the other hand, was focusing on a methodological, causal inference explanation for the paradoxical phenomenon of observational studies reporting that ICS use increases the incidence of pneumonia in contrast with other observational studies reporting that ICS use prior to a pneumonia event decreases mortality [1].