[COPD and systemic inflammation. A link for comorbidity].

Patients with chronic obstructive pulmonary disease (COPD) frequently have other chronic diseases (comorbidity) that worsen their clinical status and prognosis. Systemic inflammation may be an important pathogenic factor. The present article critically reviews some of the less well known areas in this context. For example, there is no clear definition of systemic inflammation in COPD, its prevalence is highly dependent on the inflammatory marker (or combination of markers) used in its identification, its origin is probably multifactorial and the evidence supporting an association between systemic inflammation and the presence of comorbidity in COPD is circumstantial. Finally, although several studies have evaluated the effect of inhaled glucocorticosteroids on systemic inflammation, the results are contradictory. Therefore, the association between systemic inflammation and comorbidity in COPD is a tempting, but unproven, one.