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.
What is going on in the body?
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:
Stage 0, or at risk for COPD. These people have chronic cough and sputum production. Their lung function tests are still normal.
Stage I, or mild COPD. Individuals in this group have mild limitations in their airflow and changes in their lung function tests. They generally have chronic cough and sputum production.
Stage II, or moderate COPD. People at this stage have worsening of airflow that leads to shortness of breath with exertion. Their lung function tests show marked limitations.
Stage III, or severe COPD. Individuals at this stage have severe airflow limitations that impair their quality of life. Their lung function tests are markedly abnormal.
What are the causes and risks of the condition?
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:
indoor air pollution, such as smoke from home cooking or home heating fuels
occupational dusts and chemicals
outdoor air pollution, such as motor vehicle exhaust fumes
previous viral infection of the lungs
untreated lung infections