Chronic Obstructive Pulmonary Disease (COPD) is a type of obstructive lung disease characterized by long-term poor airflow. The main symptoms include shortness of breath and cough and sputum (mucus) production. COPD is a progressive disease, which means it usually worsens over time. Eventually everyday activities, such as walking up stairs, become difficult. Tobacco smoking is the most common cause of COPD, with factors such as air pollution playing a smaller role. Diagnosis is based on poor airflow as measured by lung function tests. Most cases of COPD can be prevented by reducing exposure to risk factors, such as smoking cessation and improving air quality. There is no current cure for COPD. Some people may benefit from long term oxygen therapy or lung transplantation.