By Deborah Leader, RN 

 Medically reviewed by Daniel More, MD

Chronic obstructive pulmonary disease (COPD) is primarily caused by long-term, cumulative exposure to airway irritants such as cigarette smoke and pollution, though it can also result from asthma and other respiratory illnesses.1 Recurrent inflammation caused by these health issues changes the lungs, progressing over time and hampering breathing.

Knowing the causes and risk factors of COPD can help you better understand the extent of your risk and what you can do to prevent the disease, which is the fourth leading cause of death in the United States.2

© Verywell, 2018

Common Causes

A number of factors can contribute to the development of COPD. Most, though not all, fall into the category of long-term irritant exposure.3 Many of the causes of COPD can trigger exacerbations with worsening symptoms as well.

Smoking and Secondhand Smoke

Smoking is by far the number one cause of COPD.4 The number of cigarettes you smoke each day and the length of time that you have smoked can increase the severity of the disease.

If you have a family history of COPD, your risk is further increased by your smoking habit. Pipe and cigar smoking, smoking marijuana and cigarettes, and/or long-term exposure to secondhand smoke, amplify the inherited risk.5 

The American Lung Association estimates that 85% to 90% of COPD cases are related to cigarette smoking,6 whether by secondhand smoke or by past or present cigarette smoking.

Occupational Exposures

After smoking, being exposed to chemicals and substances such as coal mine dust, cotton dust, silica, and grain dust in the workplace, particularly long term, is among the leading causes of COPD.7 Isocyanates, natural rubber latex, animal dander, and platinum salts are among a host of other occupational agents that can damage the lungs, leading to COPD.

Occupational exposure to vapors, dust, fumes, and gases containing hazardous materials increases the risk of developing COPD by 22%.8 In fact, you can be exposed to COPD-inducing airway irritants in the workplace even if they have not been identified as causes of COPD—yet.

Pollution/Air Quality

Smog is the most widely recognized pollutant associated with respiratory issues.9 Smog is, in fact, composed of many particles in the air. But both outside air and indoor air play a role in causing COPD.

Indoor

Indoor pollutants that can irritate airways include mold, pollen, pet dander, and particles from dust mites and cockroaches, along with secondhand smoke.10

Combustible pollutants in your home can also be a problem.11 These include fireplaces (wood smoke), furnaces, heaters, and water heaters that use gas, oil, coal, or wood as fuel sources.

Outdoor

Outdoor pollutants are also risk factors for COPD. Over 133 million Americans live in areas that exceed federal health-based air pollution standards.12 Ozone and airborne particulate matter are two key pollutants that are commonly found to be at too-high levels.

Epidemiological studies now show a link between outdoor air pollutants and risk for, as well as exacerbation of, airway diseases such as COPD. There is also strong evidence that exposure to particulate matter air pollution makes COPD symptoms worse, resulting in an increased risk of death in people who have existing COPD.13

To date, no specific medical treatment has been proven to cure COPD, so it is important to reduce your exposure to causative factors as much as you can.

Risk Factors

If any of the following apply to you, you may be at increased risk of COPD, which includes two major types of lung disease—chronic bronchitis and emphysema.

Asthma

If you have asthma, even if you’ve never smoked, research shows that your risk of developing COPD may be up to 12 times higher than those who don’t have asthma.14 If you have asthma and do smoke, the risk is still higher.

Asthma, which involves episodes of inflammation and narrowing of your airways, can usually be managed with treatment.15 Recurrent inflammation due to asthma attacks can damage your lungs, so controlling the illness is an important strategy when it comes to protecting yourself against complications of asthma, including COPD.

Infections

Severe viral and bacterial lung infections in early childhood have been associated with reduced lung function and increased respiratory symptoms in adulthood, which contributes to the development of COPD.16

Chronic lung infections, such as tuberculosis, are especially linked to COPD. If you have human immunodeficiency virus (HIV), this can also speed up the development of COPD that's caused by other factors such as smoking.

Bronchitis, an infection of the bronchi, can become chronic, especially if you smoke.

Older Age

Since COPD develops over the course of years, most people are at least 40 when they're diagnosed.17 The cumulative effects of smoking, secondhand smoke, exposure to air pollutants, and recurrent infections can damage the lungs over the years.

Rest assured, however, that aging itself does not cause COPD in the absence of these risk factors.

Socioeconomic Status

Having a lower socioeconomic status poses an increased risk of developing COPD, especially during childhood.18 Researchers aren't exactly sure why but suggest that the relationship could be related to poor nutrition, untreated lung infections, exposure to irritants, or the effects of smoking, which is now more common in lower socioeconomic groups.

Being Female

Women may have a higher sensitivity to COPD risk factors than men. Females have more severe symptoms, longer years with the disease, and a higher risk of COPD-associated death than men, even when they have lower pack-years of smoking.19

This could be due to women's typically lower body weight and lung size, which can translate to a stronger impact of inhaled particles. But it can also be related to other factors, such as immune or hormonal differences.

Lifestyle trends such as the tendency to work in factories or other places where airborne toxins (including secondhand smoke) are inhaled change over time and may vary by region. So while COPD was often associated with men who work in a factory and smoke, changes in demographics and air pollution also affect who is more likely to develop the condition.

Genetics

Alpha-1-antitrypsin (AAT) deficiency is a rare genetic disorder responsible for a small number of cases of COPD.20 When COPD is due to AAT deficiency, symptoms usually begin at a younger age than when the disease is caused by smoking.

If you have an AAT deficiency, whether or not you’re exposed to smoke or other lung irritants, you can develop COPD simply because your body doesn’t make enough of the AAT protein, which protects your lungs from damage.

Other genes have been linked to decreased lung function as well, but it's unclear what role they may play in the development of COPD.14

If you are under 45 and have been diagnosed with COPD, your healthcare provider might run a test to determine if your COPD is caused by AAT deficiency, especially if you don't have other risk factors.

Possible Contributors

Other possible COPD contributing factors include:

• Deficient lung function: Sometimes, complications or developmental issues during gestation, birth, or early childhood can affect lung size or function, eventually leading to COPD.21

• Nutrition: Malnutrition can reduce respiratory muscle strength and endurance.22 For your overall health, it’s generally recommended to keep your body mass index (BMI) in the healthy range of 18.5 to 24.9. But when you have COPD and your BMI is lower than 21, mortality increases, so it’s important to monitor this number and possibly add calories to your diet if you find that your BMI is slipping under 21.

Body Mass Index (BMI) is a dated, flawed measure. It does not take into account factors such as body composition, ethnicity, sex, race, and age. 

Even though it is a biased measure, BMI is still widely used in the medical community because it’s an inexpensive and quick way to analyze a person’s potential health status and outcomes.

Pathophysiology

The COPD disease process causes a number of distinct physiologic and structural lung changes that are responsible for the varying degree of symptoms you may experience.

Inflammation

Smoking and other airway irritants cause neutrophils, T-lymphocytes, and other inflammatory cells to accumulate in the airways.23 Once activated, they trigger a further inflammatory response in which an influx of molecules, known as inflammatory mediators, navigate to the site in an attempt to destroy and remove inhaled foreign debris.

Under normal circumstances, this inflammatory response is useful and leads to healing. In fact, without it, the body would never recover from injury.

However, repeated exposure to airway irritants perpetuates an ongoing inflammatory response that actually damages lung tissue. Over time, this process causes structural and physiological lung changes that get progressively worse.

Oxidative Stress

Oxidation is a chemical process that takes place during normal metabolism and during other processes, such as illness and injury.24 The molecules formed in oxidation can harm the body.

Natural antioxidants can help prevent the harmful effects, but they are not enough to combat the oxidation that occurs with smoking, toxins, and respiratory infections. This oxidative stress adds to inflammation of the airways and leads to the destruction of the alveoli, tiny sacks in your lungs through which you absorb oxygen into your blood. Eventually, the lung damage leads to COPD.

Airway Constriction

Inhalation of toxins and lung infections results in excess mucus production, poorly functioning cilia, and lung inflammation—all of which make airway clearance especially difficult.25 Not only do the airways to become narrow and swollen due to a buildup of material, they can also episodically spasm as the airway muscles tighten in response to irritation.

When airways constrict, a person with COPD develops the hallmark symptoms of COPD, including chronic productive cough, wheezing, and dyspnea.

Mucus Build-Up

The build-up of mucus in the lungs may attract a host of infectious organisms that can thrive and multiply in the warm, moist environment of the airway and lungs.26 The end result is further inflammation, the formation of diverticula (pouch-like sacs) in the bronchial tree, and bacterial lung infection—a common cause of COPD exacerbation.

Triggers

While you can’t control every risk factor for COPD, there are some you do have control over. The two most important: don’t smoke and do your best not to expose yourself to lung irritants in your occupation and daily life.

Knowing the common triggers and minimizing exposure to them can also help you lower your risk of developing COPD or manage your existing COPD. While indoor triggers are often easier to stay away from, avoiding outdoor triggers requires more thought and planning.

Estimating Your Risk

COPD is not reversible, but it is treatable, and there are things you can do to help prevent it. Early diagnosis leads to earlier COPD treatment and a better chance of survival.

These six questions can help you get a sense of your risk of COPD. If you are concerned, be sure to speak with your healthcare provider so you can have a formal assessment.

1) Are you 40 years of age or older?
The older you are, the greater your risk of COPD if you have risk factors. Most people don’t get diagnosed until they’re in their 50s or 60s.

2) Have you been exposed to airway irritants?
A history of exposure to noxious stimuli—tobacco smoke, air pollution, workplace irritants, etc.—is part of a risk assessment for COPD.

3) Do you get short of breath more than other people?
Dyspnea (shortness of breath) is the hallmark symptom of COPD and is generally the most commonly reported symptom. It is a result of airway narrowing. If your dyspnea is persistent, has gotten worse over time, or gets more uncomfortable when you exert yourself, it may be associated with COPD.

4) Do you cough throughout the day on most days?
Coughing is a defense mechanism developed by the body in an attempt to keep the airways free of mucus or foreign debris. People with COPD often develop a chronic cough; in fact, it is one of the most common complaints you might need to talk to your healthcare provider about. A chronic cough is long-term, persistent and does not improve with medical treatment. It doesn't have to be constant or associated with phlegm—it may be intermittent and non-productive, meaning it does not produce mucus.

5) Do you cough up mucus or phlegm from your lungs most days?
These substances are normally expelled by coughing or clearing of the throat. If you have COPD, you may cough up mucus and phlegm, and you may also feel that you can't cough it all up. Any amount of chronic mucus production may be indicative of COPD.

6) Does anyone in your family have COPD?
A family history of COPD or other respiratory ailments places you at greater risk for COPD because of genetic risk factors as well as lifestyle factors that are often shared by family members.

Research shows that having a sibling with COPD increases your risk of developing the condition more than having a spouse with the disease does.27

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Additional Reading

National Heart, Lung, and Blood Institute. COPD. National Institute of Health. U.S. Department of Health and Human Services. nhlbi.nih.gov

By Deborah Leader, RN
 Deborah Leader RN, PHN, is a registered nurse and medical writer who focuses on COPD.