How is COPD Caused?


Chronic obstructive pulmonary disease (COPD) is caused by long-term inhalation of substances that irritate our lungs and airways, which leads to irreversible damage over time. 

Affected people tend to have breathing difficulties in addition to a myriad of other symptoms. These are present all the time, but the disease is marked by exacerbations where symptoms become more pronounced.

What Is COPD?

COPD is a chronic condition that causes difficulty in breathing; it can be prevented and treated but not cured. The condition is fairly common; an estimated 391.9 million people were affected globally in 2019.1 It also caused 3.23 million deaths in the same year, making it the 3rd leading cause of death worldwide.2

The term COPD encompasses two conditions called chronic bronchitis and emphysema. To understand how these conditions affect the lungs, we need to dive into the anatomy and function of the lungs for a moment. 

Anatomy of the Lungs

Imagine the lungs as two large balloons which branch off into multiple smaller balloons (the air sacs or alveoli). There are large breathing tubes (airways or bronchi) leading into the lungs and smaller tubes (bronchioles) which lead into the alveoli. These tubes take air into and out of the lungs and alveoli.

All of our organs (like the lungs, brain, heart, and kidneys) need a sufficient supply of oxygen to work properly. When we breathe in air, it travels through the airways into the lungs and then into the alveoli. From here, the oxygen in the air diffuses into our blood. 

Carbon dioxide is produced by our organs as a waste product; this is carried to the lungs by the blood. As oxygen flows out of the alveoli into the blood, carbon dioxide also flows out of the blood into the alveoli (gas exchange). The carbon dioxide then goes into the airways, and we breathe it out when we exhale.

For this process to run smoothly, our alveoli need to remain elastic with intact walls - inflating and deflating adequately as we breathe in and out, and our bronchioles and bronchi need to be open and unobstructed to allow air to move in and out.

Long-term exposure to respiratory irritants is responsible for COPD. This exposure causes inflammation and ultimately a distortion of the normal structure of the lungs and/or airways. In chronic bronchitis, inflammation of the airways leads to increased production of mucus and airway narrowing. 

Hair-like structures in the airways called cilia move in concert and help to push mucus up and out of the airways. The movement of these cilia is also affected by chronic inflammation. They cannot clear up the excess mucus produced, leading to difficulty in expiration and air trapping within the lungs.3

In emphysema, the alveoli have their walls destroyed by chronic inflammation and become far less elastic. This results in their inability to contract effectively to push air out when we exhale, as well as causing the smaller tubes leading into them to collapse. These processes result in an inability of the lungs to properly get the air out, making them hyperinflated.4

In both chronic bronchitis and emphysema, the end result is obstruction of normal airflow. Although they are described as separate entities, there is often significant overlap between the two, with some alveolar damage coexisting with airway obstruction and vice versa.5

Causes And Risk Factors Of COPD

Certain things have been found to either directly cause or significantly increase one’s chances of developing COPD. These will be discussed below.


Of the known causes of emphysema and chronic bronchitis, cigarette smoking is the most common. Cigarette smoke contains several chemicals (such as carbon monoxide and tar), which when inhaled act as lung irritants that cause inflammation and narrowing of the airways and damage to the alveoli. Thus, it can lead to both emphysema and chronic bronchitis.

As a matter of fact, cigarette smoking is such a potent cause of COPD that even exposure to secondhand smoke has been connected to the development of the condition.6

Similarly, water pipe smoking - and exposure to secondhand smoke from it - which is wrongly believed to be less harmful than cigarette smoking, is also associated with the development of COPD. Marijuana smoking in people who also smoke cigarettes has been shown to further increase the risk of COPD.8

Fumes And Dust Exposure

Exposure to toxic fumes and dust, which usually occurs at work, is also an established cause of COPD.Some identified particles include coal, silica, grain, and flour dust, as well as welding fumes and pesticides.

Air Pollution

Exposure to outdoor air pollutants like nitrogen dioxide and ozone is associated with the occurrence of COPD, especially in the developed world.9

The story is a bit different in developing countries, however, with indoor air pollution being the predominant cause. Long-term exposure to biomass fuels used in cooking or indoor heating is a more common cause of COPD in such countries.9


Several genetic causes of COPD are currently being investigated, but alpha-1 antitrypsin deficiency is the most established one.10

Alpha-1 Antitrypsin Deficiency

Certain substances in our lungs destroy harmful foreign materials, such as bacteria. These are called enzymes, and they have the ability to destroy our normal lung tissue as well. Alpha-1 antitrypsin is a protein that is produced by the liver and gets to the lungs via the blood, where it controls the activity of these enzymes.

Alpha-1 antitrypsin deficiency (AATD) is an inherited condition that is a significant risk factor for COPD. Lung enzymes are not regulated in people with AATD, resulting in the destruction of both foreign materials and the alveolar walls - leading to emphysema.11

Chronic Respiratory Infections During Childhood

The chances of developing COPD are much higher in smokers who had pneumonia in childhood; the risk is even higher in people who had both childhood asthma and pneumonia.12

Symptoms of COPD

Below are some of the symptoms of COPD:

  • A cough that lasts a long time
  • Bringing up a lot of sputum (mucus/phlegm), which could range in appearance from clear to yellowish or greenish
  • Breathlessness when carrying out non-strenuous activities or even at rest
  • Repeated respiratory infections
  • Fatigue
  • Wheezing

Although the disease is a long-term one, patients tend to have exacerbations. These are identified by a marked worsening of symptoms, happening in a short time. Exacerbations are often caused by bacterial or viral infections, and they worsen the destruction of the lungs and the outlook for patients.12

How COPD is Treated

Treatment options for COPD are varied, and you and your healthcare provider will decide on the best option(s) for you. These include:

  • Bronchodilator drugs that can open the airways to improve breathing
  • Anti-inflammatory medicines - Steroids could be prescribed in a pill or inhaler form to reduce airway inflammation
  • Antibiotics - These are given during exacerbations caused by bacterial respiratory infections
  • Antiviral drugs - Viral infections like influenza can also cause exacerbations. In such cases, antiviral drugs may be prescribed
  • Oxygen therapy - You might be given additional oxygen if your blood oxygen levels are found to be low
  • Vaccines - Prevention of respiratory infections also helps to prevent acute exacerbations. You might therefore be given vaccines like the flu vaccine or the pneumococcal vaccine
  • Pulmonary rehabilitation - A comprehensive program designed to improve the overall health and quality of life of people with respiratory conditions
  • Lung transplant - This is often the last resort in selected patients.

Outlook For COPD

Because damage to the lungs and airways is irreversible, COPD cannot be cured. The outlook for patients depends on factors like the severity of the disease, frequency of exacerbations, and continued exposure to respiratory irritants. Patients with a milder form of the disease, fewer exacerbations, and little or no irritant exposure have more favourable outcomes.

Additionally, because smoking also increases the risk of conditions like lung cancer and coronary heart disease, these are often found in patients with COPD. Other conditions commonly found with COPD include pulmonary hypertension, heart failure, diabetes, and mental health issues like anxiety and depression. The presence of any of these other diagnoses worsens outcomes in COPD patients.

Reducing Your Risk Of COPD

There are things you can do to reduce your chances of getting COPD and prevent worsening of the disease when you have it:

  • Stop smoking - This significantly reduces your chances of developing the disease as well as disease exacerbations. You can get help here
  • Avoid environments with poor air quality
  • Be physically active
  • Eat a balanced diet
  • Seek psychological and social support - This can improve mental health and well-being. Educational resources and support services are available from the British Lung Foundation, the American Lung Association, and the Lung Foundation Australia


COPD is a progressive and irreversible respiratory disease that can significantly worsen a person’s quality of life. The majority of cases are caused by cigarette smoking, but air pollution and exposure to other lung irritants can also result in COPD. Although it cannot be cured, it is potentially treatable and preventable. If you are at high risk of developing it or if you already have COPD, speak to your healthcare provider today about things you can do to ensure you live a long and healthy life!


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  8. Tan WC, Lo C, Jong A, Xing L, FitzGerald MJ, Vollmer WM, et al. Marijuana and chronic obstructive lung disease: a population-based study. CMAJ [Internet]. 2009 Apr 14 [cited 2022 Aug 23];180(8):814–20. Available from:
  9. Hansel NN, McCormack MC, Kim V. The effects of air pollution and temperature on COPD. COPD: Journal of Chronic Obstructive Pulmonary Disease [Internet]. 2016 May 3 [cited 2022 Aug 22];13(3):372–9. Available from:
  10. Silverman EK. Genetics of COPD. Annu Rev Physiol [Internet]. 2020 Feb 10 [cited 2022 Aug 23];82:413–31. Available from:
  11. Brode SK, Ling SC, Chapman KR. Alpha-1 antitrypsin deficiency: a commonly overlooked cause of lung disease. CMAJ [Internet]. 2012 Sep 4 [cited 2022 Aug 23];184(12):1365–71. Available from:
  12. Wedzicha JA, Seemungal TA. COPD exacerbations: defining their cause and prevention. Lancet [Internet]. 2007 [cited 2022 Aug 23];370(9589):786–96. Available from:
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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