Inhaled corticosteroids and pneumonia mortality in COPD patients

Abstract

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]. The “paradoxical” effect of inhaled corticosteroids increasing pneumonia incidence in COPD but reducing post-pneumonia and all-cause mortality is no paradox but due to selection and immortal time biases in the observational studies of mortality http://bit.ly/2Yd3hDh