Chronic obstructive pulmonary disease (COPD) is one of the most common lung diseases. It makes it difficult to breathe. There are two main forms of COPD:

• Chronic bronchitis, defined by a long-term cough with mucus
• Emphysema, defined by destruction of the lungs over time

Most people with COPD have a combination of both conditions.

Smoking is the leading cause of COPD. The more a person smokes, the more likely that person will develop COPD although some people smoke for years and never get COPD.

In rare cases, nonsmokers who lack a protein called alpha-1 antitrypsin can develop emphysema.

Other risk factors for COPD are:

• Exposure to certain gases or fumes in the workplace
• Exposure to heavy amounts of secondhand smoke and pollution
• Frequent use of cooking gas without proper ventilation