Chronic obstructive pulmonary disease (COPD) is a type of obstructive lung disease characterized by long-term breathing problems and poor airflow. The main symptoms include shortness of breath and cough with sputum production. COPD is a progressive disease, meaning it typically worsens over time. Eventually, everyday activities such as walking or getting dressed become difficult. Chronic bronchitis, and emphysema are older terms used for different types of COPD. The term "chronic bronchitis" is still used to define a productive cough that is present for at least three months each year for two years. Those with such a cough are at a greater risk of developing COPD. The term "emphysema" is also used for the abnormal presence of air or other gas within tissues.The most common cause of COPD is tobacco smoking, with a smaller number of cases due to factors such as air pollution and genetics. In the developing world, common sources of air pollution are wood combustion and cooking fires. Long-term exposure to these irritants causes an inflammatory response in the lungs, resulting in narrowing of the small airways and breakdown of lung tissue. The diagnosis is based on poor airflow as measured by lung function tests. In contrast to asthma, the airflow reduction generally does not improve much with the use of a bronchodilator.Most cases of COPD can be prevented by reducing exposure to risk factors. This includes decreasing rates of smoking and improving indoor and outdoor air quality. While treatment can slow worsening, no cure is known. COPD treatments include smoking cessation, vaccinations, respiratory rehabilitation, and often inhaled bronchodilators and steroids. Some people may benefit from long-term oxygen therapy or lung transplantation. In those who have periods of acute worsening, increased use of medications, antibiotics, steroids, and hospitalization may be needed.As of 2015, COPD affected about 174.5 million people (2.4% of the global population). It typically occurs in people over the age of 40. Males and females are affected equally commonly. In 2015, it caused 3.2 million deaths, more than 90% in the developing world, up from 2.4 million deaths in 1990. The number of deaths is projected to increase further because of higher smoking rates in the developing world, and an ageing population in many countries. It resulted in an estimated economic cost of US$2.1 trillion in 2010.