Chronic obstructive pulmonary disease as a systemic disease: an epidemiological perspective

Chronic obstructive pulmonary disease (COPD) has been increasingly recognised as a systemic disease. The hormonal, metabolic and musculoskeletal implications of the generalised processes involving oxidative stress, inflammatory mediators, cytokines, and endocrine hormones have only begun to be understood. Only a few studies have looked into the epidemiology of inflammatory markers in patients with chronic obstructive pulmonary disease. Common extrapulmonary effects of chronic obstructive pulmonary disease include skeletal muscle dysfunction, wasting and osteoporosis. The resulting effects of a systemic inflammation can be measured at specific extrapulmonary organs such as skeletal muscle or in more general terms using body composition, body weight or derived measures, and only a few studies have set the parameters in an epidemiological context. Nevertheless, these studies indicate an association between inflammatory markers and forced expiratory volume in one second not only in subjects with severe chronic obstructive pulmonary disease. Also, it is increasingly clear that systemic markers in chronic obstructive pulmonary disease have important effects on prognosis.