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Bronchitis Causes

Bronchitis is broadly defined as an inflammation of the bronchiole tubes that deliver air to the lungs.

Smoking is the leading cause of chronic bronchitis. [© Shutterstock, 2010]
© Shutterstock, 2010
Smoking is the leading cause of chronic bronchitis.

Bronchitis Causes

Bronchitis is broadly defined as an inflammation of the bronchial tubes that deliver air to the lungs, but bronchitis causes are many and varied. There are two distinct types of bronchitis: acute and chronic. Acute bronchitis usually follows quickly on the heels of a bacterial or viral infection that spreads to the lungs, though it is sometimes due to environmental factors. Chronic bronchitis is a serious and often permanent condition caused by smoking or by inhaling air pollutants or chemicals found on factory jobsites. In some cases, it may also be related to acid reflux. Bronchitis is considered chronic if symptoms persist at least three months out of the year, over the course of two years or more.

Chronic Bronchitis Causes

Chronic bronchitis is one of the conditions categorized as chronic obstructive pulmonary disease, or COPD; emphysema is the other condition in this category, and asthma is also sometimes grouped in.

Chronic bronchitis results when the lining of the bronchial tubes thickens permanently, which gradually worsens over time and severely limits the patients ability to breathe. The cause of chronic bronchitis is nearly always environmental. According to the American Lung Association, smoking is by far the leading cause of COPD, though exposure to industrial pollutants found in factories and mining sites account for 19.2 percent of COPD cases. Among those who have never smoked, work-related chemicals cause 31.1 percent of cases.

Whatever their source, irritants damage the tiny hairs, called cilia, that line the bronchials and help clear the air passages of mucus. Even healthy lungs produce mucus, but the cilia help sweep it out so it can be absorbed by saliva. In addition to cilia damage, the problem is exacerbated by the fact that irritants also cause the mucus glands to swell, further blocking the airways. And in cases of advanced chronic bronchitis, the bronchial walls start to degenerate.

Acute Bronchitis and Infection

Acute bronchitis is most often the result of an upper respiratory infection, which can either be bacterial or viral. Usually when acute bronchitis follows a cold or the flu, the primary infection is viral and spreads to the nose, throat and down to the lungs. The viral infection, in turn, makes the lungs susceptible to a secondary, bacterial infection.

Chronic bronchitis can also be a cause of acute bronchitis. In lungs with damaged or non-existent cilia, mucus accumulates and is excreted only by coughing, a classic symptom of bronchitis. The absence of cilia makes the lungs more vulnerable to both bacterial and viral infection. In this way, chronic bronchitis often contributes to cases of acute bronchitis.

Acute Bronchitis and Environmental Irritants

Though infection is a common cause of acute bronchitis, the same environmental irritants that cause chronic bronchitis can also lead to acute bronchitis. According to the National Heart Lung and Blood Institute, smoking, as well as exposure to second-hand smoke and air pollution, can inflame the bronchial tubes and cause acute bronchitis. Household cleaning chemicals and fires may also be culprits. If nothing else, environmental irritants can make a case of acute bronchitis worse.

People exposed to harmful chemicals on the job are said to have occupational bronchitis. Over time, these chemicals can cause the bronchial tubes to thicken permanently, which leads to chronic bronchitis. In the short-term, however, people who inhale industrial chemicals or breathe in dust that gets kicked up at mining sites are at risk of contracting acute bronchitis. The condition often clears up once the patient has a chance to recover away from the job site.

Gastroesophageal Reflux Disease and Bronchitis

According to the Mayo Clinic, acute bronchitis may also result from gastroesophageal reflux disease, or GERD. Though it is not nearly as common a cause as infection or environmental irritants, GERD sufferers should be aware that bronchitis may be a complication they will face. GERD is a condition in which acids from the stomach consistently push back up through the esophagus. This irritates the lining of the esophagus and the throat, and frequently causes heartburn.

It is thought that GERD results from problems with the esophageal sphincter, a muscle that is supposed to close off the stomach from the esophagus. Pregnant women and those who have a hiatal hernia or scleroderma are considered especially at risk. In addition, obesity has also been linked to GERD. Though most of GERDs symptoms affect digestion, many are related to lung function. Wheezing and coughing are common, as are sore throat, hoarseness and difficulty swallowing.

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