Chronic bronchitis belongs to a larger family of medical conditions known as chronic obstructive pulmonary disease (COPD). The term COPD is given to any condition that causes difficulty in breathing as a result of constant blocking of the airways.
Bronchitis is defined by cough, usually with some sputum production. The cough happens because the air tubes are permanently inflamed and secrete mucus. When cough and sputum have been present for more than 3 months in each of 2 consecutive years, the condition is called chronic bronchitis. In North America, about 1 person in 20 suffers from chronic bronchitis.
Smoking for many years causes about 90% of chronic bronchitis cases, and the great majority of people with chronic bronchitis are over 45 years of age. The risk of chronic bronchitis is also increased in workers employed in certain occupations such as coal mining, welding, asbestos work, or grain handling.
When breathing becomes more difficult for a person with chronic bronchitis, he or she may be experiencing an acute exacerbation of chronic bronchitis (AECB). During an acute exacerbation, breathing becomes more difficult because of further narrowing of the airways and secretion of large amounts of mucus that is often thicker than usual.
The further narrowing of airways in people with chronic bronchitis that results in AECB can be caused by allergens (e.g., pollens, wood or cigarette smoke, pollution), toxins (a variety of different chemicals), or acute viral or bacterial infections.
Bacterial infections are usually associated with mucus that turns a yellow or greenish color and is typically much thicker than usual. Colored mucus does not necessarily mean the person has a bacterial infection, however.
When a person has severe chronic lung disease from smoking, it may take something as little as a chest cold to make their breathing so severe that they must be hospitalized.