Co-morbid disease in COPD: more than a coincidence

Chronic obstructive pulmonary disease (COPD) is a major cause of disability and death worldwide. Its prevalence and mortality are increasing disproportionately among the elderly, women, persons of lower socioeconomic status, and the populations of developing countries (Anthonisen 1988; Borson et al 1998; Andreassen and Vestbo 2003). There is increasing recognition that COPD is a complex disorder, with many associated co-morbidities. The term “co-morbid” has traditionally been interpreted as “a medical condition existing simultaneously but independently with another condition in a patient.” However, this does not seem to fit the more recent research on patients with COPD as co-morbid conditions occur more frequently in these patients that would be expected by chance...