Vitamin D in COPD - A Pleiotropic Micronutrient in a Multisystem Disease

Chronic Obstructive Pulmonary Disease (COPD) is a debilitating disease affecting an estimated 3 million people in the United Kingdom. It is characterised by progressive and irreversible airway obstruction and lung parenchymal damage, and by multisystem involvement including skeletal muscle impairment, systemic inflammation, and an increased prevalence of osteoporosis, cardiovascular disease and lung cancer. Patients with COPD have reduced dietary intake of vitamin D, spend a reduced amount of time outdoors and have been shown to have lower levels of 25-hydroxyvitamin D (25[OH]D) than age-matched subjects without COPD. The active metabolite of vitamin D, 1,25-dihydoxyvitamin D (1,25[OH]2D), is a pleiotropic hormone with effects on lung development and function, the immune system and musculoskeletal function; vitamin D deficiency also associates with increased prevalence of cardiovascular disease and cancer. This article focuses on the evidence that vitamin D deficiency is highly prevalent in patients with COPD and reviews associations between vitamin D status and lung function, muscle function and risk of osteoporosis, cardiovascular disease and cancer. The potential pathological mechanisms which may be involved are also discussed.