What Causes Chronic Obstructive Pulmonary Disease (COPD)?

Medically reviewed by Susan Russell, MD

Chronic obstructive pulmonary disease (COPD) is an inflammatory, progressive lung disease that constricts the airways and makes breathing difficult. Long-term exposure to harmful substances and irritants—like cigarette smoke, dust, fumes, chemicals, and air pollution—is the most common risk factor for COPD. This can lead to two main types of COPD: chronic bronchitis and emphysema.

The airways are normally elastic and stretchy and can easily inflate and deflate as you breathe. When you inhale, the air sacs (alveoli) fill with air, expanding like tiny balloons. The air sacs relax and deflate when you exhale, moving air out of the lungs.

COPD causes the airways to become narrowed, and less air flows in and out, making breathing difficult. This can occur for a number of reasons:

• Mucus clogs or blocks part of the airway

• The airways are swollen and inflamed

• The lungs, airways, and air sacs become damaged and less stretchy

• The walls between air sacs are destroyed

Related: What Causes Asthma?

Types of COPD and Their Causes

Two main types of COPD are associated with damage to the airways and breathing difficulties. These types include:

• Chronic bronchitis: The airways (bronchial tubes) are irritated, inflamed, and narrowed after long-term exposure to irritants. This irritation causes mucus to build up. Many people with the disease cough up mucus (phlegm). The combination of mucus and narrowed airways can make breathing difficult.

• Emphysema: The alveoli are damaged due to repeated exposure to harmful irritants. This damage causes the air sacs to lose their elasticity and shape and become saggy. This makes it harder for the lungs to expand to breathe in and out.

Both chronic bronchitis and emphysema make breathing difficult and can lead to shortness of breath, a persistent cough, wheezing, and other symptoms. Most people with COPD have both chronic bronchitis and emphysema.

What's The Difference Between Chronic Bronchitis and Emphysema?

Chronic bronchitis and emphysema have a few differences, including:

• Bronchitis affects the airways, whereas emphysema affects the air sacs.

• Bronchitis causes an excess of mucus in the lungs, leading to chronic cough.

• Bronchitis is reversible, and emphysema is not.
  

Is COPD Hereditary?

COPD most often develops due to long-term exposure to cigarette smoke, dust, chemical exposure at work, or air pollution. A small number of people have a hereditary genetic disorder that increases their risk of developing COPD.

A genetic condition called alpha-1 antitrypsin (AAT) deficiency is associated with an increased risk of COPD. AAT is a protein produced in the liver that helps protect the lungs. Your lungs are more vulnerable to damage from smoking and environmental pollutants if your liver does not make enough AAT.

Up to 3% of people with COPD are thought to have AAT deficiency. AAT deficiency occurs if you inherited a mutated (changed) AAT gene from both parents. You are a carrier for the condition but probably don't have the deficiency if you inherited a mutated gene from only one parent.

Inherited AAT deficiency is linked to a higher risk of COPD and a greater chance of developing the disease at a young age. Not everyone with this deficiency will develop COPD. You can lower your risk by not smoking and taking precautions to avoid exposure to harmful chemicals and air pollution.

Talk to a healthcare provider about testing to see if you have inherited AAT deficiency if you have a parent with COPD. They can order a blood test to check the level of AAT in your blood. Low levels of AAT may indicate you have a deficiency. A healthcare provider may advise genetic testing to find the mutation.

Who Gets COPD?

Some people are more likely to develop COPD than others:

• Age: COPD is commonly diagnosed in people aged 40 and older.

• Family history: People with inherited AAT deficiency and smokers with a family history of COPD are at a higher risk.

• Sex: Rates of COPD are higher in women than in men. Some evidence suggests that women may be more vulnerable to cigarette smoke and other irritants than men. Women are also more at risk of early-onset and more severe COPD.

Risk Factors

A risk factor is something that increases a person's chances of developing a disease. COPD risk factors include smoking, occupational exposure to irritants, pollution, and asthma.

Smoking

Smoking is the leading cause of COPD. Up to 90% of COPD cases are linked to cigarette smoking. The more a person smokes, as well as the longer they smoke, can increase the risk and severity of the disease.

Cigarette smoking creates harmful toxins that can weaken the lungs and increase the risk of infection, narrow airways, and destroy air sacs in the lungs. These complications can contribute to a higher risk of COPD.

Secondhand smoke can increase the risk of the disease. Even non-smokers regularly exposed to toxins in smoke are at risk. Vaping nicotine, marijuana (cannabis), and smoking cannabis flower also increase a person's chances of developing COPD.

Occupational Exposure to Irritants

Exposure to chemicals and fumes of harmful substances at work can damage the lungs and increase your risk of COPD. Long-term exposure to grain and flour dust, coal mine dust, welding fumes, silica, cadmium, and isocyanates (common in auto body paints and varnishes) have all been linked to COPD.

Indoor and Outdoor Pollution

Both indoor and outdoor pollutants can irritate airways and harm lung health. Smog (smoke and fog) is outdoor air pollution that contains many particles. Some of these particles can damage the lungs and airways and increase your chances of developing COPD.

Indoor pollutants, such as mold, pet dander, dust mites, and asbestos, can have detrimental consequences on lung health. Combustible pollutants like firewood smoke and furnaces that use gas or coal can also lead to the development of COPD.

Asthma

Having asthma as a child or as an adult is associated with a higher risk of COPD. Research has shown that people with asthma have a 12.5 times higher risk of the disease than those who do not.

Childhood asthma has been shown to reduce lung function, which can persist well into adulthood and raise the risk of COPD. Not everyone with asthma will develop COPD. Proper treatment of asthma and not smoking can lower the risk of COPD and other lung health complications.

Related: What Causes Sleep Apnea?

A Quick Review

COPD occurs when damage from smoking or long-term exposure to harmful irritants—chemical fumes, dust, and pollution—causes the airways to become inflamed and swollen, making it hard to breathe. A family history of the disease and a personal history of asthma may also increase the risk of the disease. Not smoking and protecting yourself from harmful irritants and chemicals can help protect your lungs and reduce your risk.

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