pulmonary disorders
Chronic Obstructive Pulmonary Disease (COPD)
Etiology of COPD
There are 2 main causes of COPD: Smoking (and less often other inhalational exposures) Genetic factors Of all inhalational exposures, cigarette smoking is the primary risk factor in most countries, although only about 15% of smokers develop clinically apparent COPD; an exposure history of 40 or more pack-years is especially predictive. Smoke from indoor cooking and heating is an important causative factor in countries where indoor fires are commonly used for cooking or heating. People who smoke and have preexisting airway reactivity (defined by increased sensitivity to inhaledmethacholine), even in the absence of clinical asthma, are at greater risk of developing COPD than are those without. Low body weight, childhood respiratory disorders, and exposure to passive cigarette smoke, air pollution, and Overview of Environmental and Occupational Pulmonary Diseases (eg, mineral dust, cotton dust) or inhaled chemicals (eg, cadmium) contribute to the risk of COPD but are of minor importance compared with cigarette smoking. The best-defined causative genetic disorder is Alpha-1 Antitrypsin Deficiency , which is an important cause of emphysema in nonsmokers and markedly increases susceptibility to disease in smokers. More than 30 genetic alleles have been found to be associated with COPD or decline in lung function in selected populations, but none has been shown to be as consequential as alpha-1 antitrypsin. 