Chronic bronchitis is a type of chronic obstructive airway disease, or COPD. People with COPD have limitations in the flow of air through their airways. Chronic bronchitis is an ongoing inflammation of the breathing tubes.
Chronic bronchitis results from long-term exposure of the airways to irritants. These irritants include tobacco smoke, air pollution, and chemicals. They cause the airways to secrete excess mucus and to become inflamed. With time, the inflammation becomes widespread. The cells lining the airways change. The glands that produce the mucus become enlarged. Inflammation and excess mucus combine to cause a cough that produces sputum, or phlegm, almost every day.
The World Health Organization, also known as WHO, has recently developed a classification system for the severity of chronic bronchitis and other forms of COPD. There are four stages of severity, as outlined below:
Cigarette smoking is the most common cause of chronic bronchitis. The risk goes up with the amount of tobacco smoked and the number of years of smoking. Chronic bronchitis is most common in countries where smoking is prevalent. It is less common in countries where people smoke less. Passive smoking, or exposure to secondhand smoke, does increase a person's risk for chronic bronchitis.
Other risk factors for chronic bronchitis include the following: