Chronic obstructive pulmonary disease (COPD) is a lung disease that can have several causes. Although smoking is the most common cause of COPD, there are other factors that can cause it as well. Some people smoke for many years and never develop the disease, while others develop COPD even without a history of smoking.

Read on to discover what causes COPD, along with seven of the most common risk factors.

What’s the Main Cause of COPD?

COPD is caused by inhaling certain gases or particles over an extended time period. Being exposed to these substances leads to lung damage and makes it harder for air to flow in and out of the lungs and airways. This reduced airflow makes it hard to breathe.

When you inhale, air travels down your bronchial tubes (airways). It then moves deeper into the lungs through the bronchioles, which are long, thinner tubes. The bronchioles send the air to the alveoli, which look like small, elastic air sacs.

In healthy lungs, breathing brings in oxygen and releases carbon dioxide. But in people with COPD, damage to these structures makes it harder to breathe.

There are several ways COPD can develop:

• The walls between the air sacs in your lungs break down.
• Your air sacs or airways become more rigid and can’t expand and contract properly.
• The walls of your bronchial tubes become inflamed and thickened.
• Excess mucus builds up in the airways, which can cause clogs.

When these changes happen, COPD may develop. The two main types of COPD are emphysema and chronic bronchitis.

7 Risk Factors for COPD

Several factors can raise your risk of developing COPD. Remember, not everyone with these risk factors will develop COPD. Talk to your healthcare provider if you’re concerned you might be at high risk for COPD.

1. History of Smoking

About 75 percent of people with COPD have smoked at some point in their lives. The longer you smoke tobacco, the higher your risk of developing COPD. One study found that it takes an average of 30 years of smoking for COPD to develop.

Not all people who smoke get COPD. One study found that about 20 percent of people who smoke tobacco will be diagnosed with the disease. Having a family history of COPD raises your risk even more if you smoke.

Some people think pipe or cigar smoking is safer than cigarette smoke. But studies show that these types of smoking can also lead to COPD. Vaping and smoking marijuana also increase your COPD risk.

2. Inhalation of Certain Irritants

Breathing in certain lung irritants, especially with frequent and long-term exposure, can raise your risk of COPD.

Common irritants include:

• Air pollution
• Dust
• Smoke from heating or cooking fuels
• Chemical fumes
• Smoke from wood- or coal-burning stoves

Working in environments where you’re exposed to irritants such as chemical vapors, asbestos, or diesel exhaust can increase your risk significantly. About 14 percent of all COPD cases are linked to occupational exposure (exposure in the workplace). Among people who have never smoked, about 31 percent of COPD diagnoses are linked to exposure at work.

You can lower your risk of developing COPD even if you’re exposed to these irritants. For example, wear a respirator when working around airborne particles. If you’re using a wood-burning stove or using heating fuels indoors, make sure the area is well ventilated.

3. Exposure to Secondhand Smoke

While smoking puts people at risk of COPD, you’re also at risk if you’re frequently around a person who smokes. That’s because you’re likely inhaling secondhand smoke from the other person’s smoking. Secondhand smoke from cigarettes, hookahs, pipes, e-cigarettes, or cigars can all be dangerous.

One study of people who don’t smoke found that those exposed to secondhand smoke had twice the risk of developing COPD compared to those who weren’t around people who smoke.

If someone close to you smokes, avoid being near them when they’re smoking. No amount of smoke exposure is considered safe.

4. Asthma, HIV, or Other Conditions

People who have asthma may be at higher risk for developing COPD. That risk is even higher if you have asthma and you also smoke.

Other conditions may also raise your risk of COPD. For instance, human immunodeficiency virus (HIV) and tuberculosis are two conditions that can increase your chances of developing COPD.

5. Older Age

As people age, their risk of COPD increases. Most people with the condition are 40 years old or older when their COPD symptoms start.

One study found that COPD was not very common in people under age 50. The researchers calculated how common COPD was in the following age groups:

• Age 20 to 25 — 0.18 percent
• Age 26 to 30 — 0.95 percent
• Age 31 to 35 — 1.39 percent
• Age 36 to 40 — 1.66 percent
• Age 41 to 45 — 2.10 percent
• Age 46 to 50 — 3.65 percent

6. History of Childhood Respiratory Illnesses

People who had respiratory infections when they were children may have a higher risk of COPD. One study found that respiratory issues in childhood led to reduced lung function later in life. For example, people who had asthma, ear issues, and respiratory disorders as children had a higher risk of COPD as adults.

7. Alpha-1-Antritrypsin Deficiency

Around 5 percent of people diagnosed with COPD have the genetic disorder alpha-1-antitrypsin (AAT) deficiency, or alpha-1. People with alpha-1 produce a limited amount of AAT, a protein that helps protect the lungs. In addition to COPD symptoms common in other forms of COPD, people with alpha-1 may experience year-round allergy symptoms.

A simple blood test can screen for the genetic variant that causes alpha-1. Having alpha-1 doesn’t necessarily mean you have or will develop COPD, but it can help identify your risk and guide the best strategies for preventing or treating COPD.

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