COPD, or chronic obstructive pulmonary disease, is a progressive disease that makes it hard to breathe. Progressive means the disease gets worse over time.
COPD can cause coughing that produces large amounts of a slimy substance called mucus, wheezing, shortness of breath, chest tightness, and other symptoms.
Cigarette smoking is the leading cause of COPD. Most people who have COPD smoke or used to smoke. However, up to 25 percent of people with COPD never smoked. Long-term exposure to other lung irritants—such as air pollution, chemical fumes, or dusts—also may contribute to COPD. A rare genetic condition called alpha-1 antitrypsin (AAT) deficiency can also cause the disease.