Frequent chronic obstructive pulmonary disease exacerbators: how much real, how much fictitious?

Exacerbations are important events in the natural history of chronic obstructive pulmonary disease (COPD). The higher the number of COPD exacerbations, the worse are the clinical and economical consequences. The distribution of COPD exacerbations is however highly variable. Some patients do not exhibit exacerbations at all whereas others suffer frequent events (i.e., "frequent COPD exacerbators"). We review the scientific evidence regarding the impact of COPD exacerbation frequency and assess whether or not these frequent exacerbators represent a unique population of COPD patients with higher morbidity and mortality risks. A definition of "frequent COPD exacerbators" is suggested to differentiate it from other related terms, such as "treatment failure" and "recurrence." The standardization of this terminology seems to be necessary to further identify COPD phenotypes in patients who have an individual susceptibility to develop frequent exacerbations. It can also be of help to refine the most appropriate therapeutic and preventative measures.