Chronic Bronchitis And Smoking

What is chronic bronchitis?

Bronchitis is defined by the NHS as a condition caused by infections in the respiratory system, leading to irritation and inflammation in the windpipes before continuing down into the lungs. The diagnosis would change to chronic bronchitis if the condition lasts for 3 months per year for over 2 years continuously.1

Like emphysema, chronic bronchitis is a type of chronic obstructive pulmonary disease (COPD) that disrupts lung functions and causes difficulties in breathing. It mainly occurs amongst the middle-aged and older population, and the symptoms can be heavily worsened by smoking.2 Whilst emphysema causes damage directly to the lungs, chronic bronchitis is caused by inflammation in the airways, leading to an overproduction of mucus in the bronchi. However, both chronic bronchitis and emphysema can cause similar effects that are detrimental to individuals’ lungs and other muscle functions.3,4 

Symptoms of Chronic Bronchitis

  • Coughing: an individual may experience cold-like symptoms due to infections and irritations in the airways. These will worsen over time if untreated.
  • Breathing difficulties: these can arise due to the overproduction of mucus, causing a blockage in the airways.
  • Weakness during exercise: as physical activities require an increased amount of oxygen intake for muscle contractions,5 experiencing breathing difficulties may lead to muscle weakness. 
  • Breathing with rattling sounds 
  • Frequent colds and flu: suffering from chronic bronchitis that is not effectively treated increases the chance of further bacterial or viral infections in the respiratory system. 

The symptoms gradually become apparent over time, and the severity varies from one to another. Some patients may also experience swelling in their limbs and weight loss.4 

Does smoking cause chronic bronchitis?

Smoking, as one of the leading risk factors of COPD,2 is the major cause of chronic bronchitis.1 Clinical research indicates that reducing smoking habits over time could effectively reduce the symptoms of chronic bronchitis, but that the resumption of smoking would promote the symptoms further.

Smoking causes inflammation of the bronchi

There are thousands of toxic chemicals present in cigarette smoke, both in the form of gas and aerosol. As the gas component gets absorbed during smoking, the aerosol particles get trapped in the airways, causing irritations and inflammation.7 Different toxins may damage the bronchi in different ways (table 1).

Toxic substance: Nicotine 

State: Liquid (Aerosol)

How it damages the airways: Increases specific nicotinic receptors in airway smooth muscle (ASM), causing hyper-responsive airways and inflammation.11,12

Toxic substance: Acrolein

State: Liquid (Aerosol)

How it damages the airways: Impairs cilia function and weakens the defences in the airways.7 

Toxic substance: Tar

State: Aerosol

How it damages the airways: Impairs cilia function and narrows the airways. 

There is also some evidence to suggest that toxic gases in cigarettes, such as formaldehyde and carbon monoxide, directly trigger bronchi inflammation.8 Their impact on chronic bronchitis is overshadowed by other conditions such as cancer and carbon monoxide poisoning.9,10  

In short, overexposure of the bronchi to the toxic chemicals from cigarettes will trigger an overt response of our physical barriers. An excessive amount of mucus is produced, ASM over-contracts, and other physical defences in the airways become overloaded. Chronic inflammation of the bronchi is a biomarker of chronic bronchitis.13  

Constant inflammation makes the bronchi less functional

Whilst inflammatory responses are helpful for the clearance of harmful chemicals, chronic airway inflammation can cause further damage to the bronchi. Acute inflammation will cause the bronchi to no longer be able to clear out the infection when the toxic substances are “stuck” in the airways for a long time. Therefore, our immune cells, such as CD8+T cells and neutrophils, would become responsible for chronic inflammation.13 

When chronic inflammation occurs due to habitual cigarette smoking, an increased amount of mucus is produced, and the airways become narrower, causing breathing difficulties. Furthermore, chronic inflammation triggered by smoking would enhance cell damage, leading to further defects of bronchial function and potentially cancer.  

Exposure to second-hand smoke

Even if you are not a smoker, exposure to second-hand smoke would put similar stresses on your health. When you are around a smoker, you breathe in the irritants involuntarily. The same substances enter your nose and mouth, and the same detrimental effects would occur in the bronchi. Children are especially vulnerable to second-hand smoke, as their airways are not fully developed. If someone is smoking, especially indoors, any children nearby would be exposed to the same types of toxins and be put at a higher risk of developing chest infections.16

Can the effects of smoking be reversed?

Although the disease cannot be cured,1 the symptoms of chronic bronchitis can be treated by structured physical training and by quitting smoking.17  

Whilst quitting habitual smoking is challenging, it is the most effective method to improve quality of life and prevent further damage to the respiratory system. Quitting smoking has been widely used as a treatment for chronic bronchitis, as it effectively reduces the severity of chronic inflammation and increases patients’ lifespan.

A moderate level of exercise can be combined with giving up smoking to reduce the symptoms of chronic bronchitis, as it allows the strengthening of our smooth muscles in the airways and lungs.17 

Tips on how to quit smoking

Cigarette smoking is addictive mainly due to the nicotine reliance that smokers develop.18 A combination of medical treatments and self-help plans may help with giving it up. Here are some tips on how to quit smoking:

  • Nicotine replacement therapy: patients are given nicotine in different forms, with the toxic chemicals removed. This can help to reduce withdrawal symptoms.
  • Moderate exercise: adopting new hobbies can help to shift focus from smoking.
  • Talking to doctors and therapists about how to overcome physical and psychological reliance. 
  • Calling a smoking helpline.
  • Setting up new targets and rewards for quitting smoking. 


Cigarette smoking is the leading cause of chronic bronchitis. The harmful chemicals that stay in the airways cause damage, such as an over-secretion of mucus, cilia dysfunction, and infections. Other than irritations in the bronchi, chronic inflammation is the most significant indicator of chronic bronchitis. Therefore, quitting smoking is the most important way to treat the disease and protect your loved ones from the risk of developing the disease. Despite having no cure for chronic bronchitis, treatments can be carried out to drastically improve your quality of life. 


  1. NHS Choices. Bronchitis [Internet]. NHS. 2019. Available from:
  2. National Health Service. Chronic Obstructive Pulmonary Disease (COPD) [Internet]. NHS. 2019. Available from:
  3. ‌Medline Plus. Emphysema [Internet]. National Library of Medicine; 2017. Available from:
  4. ‌MedlinePlus. Chronic Bronchitis [Internet]. National Library of Medicine; 2018. Available from:
  5. ‌Ferguson RA, Ball D, Krustrup P, Aagaard P, Kjaer M, Sargeant AJ, et al. Muscle oxygen uptake and energy turnover during dynamic exercise at different contraction frequencies in humans. The Journal of Physiology. 2001 Oct;536(1):261–71.
  6. ‌Rosenberg SR, Kalhan R. Chronic Bronchitis in Chronic Obstructive Pulmonary Disease. Magnifying Why Smoking Cessation Still Matters Most. Annals of the American Thoracic Society [Internet]. 2016 Jul [cited 2019 Aug 11];13(7):999–1000. Available from:
  7. ‌Centers for Disease Control and Prevention. Pulmonary Diseases [Internet]. Centers for Disease Control and Prevention (US); 2010. Available from:
  8. ‌Rastogi S, Mathur N. Respiratory effects due to occupational exposure to formaldehyde: Systematic review with meta-analysis. Indian Journal of Occupational and Environmental Medicine. 2007;11(1):26.
  9. ‌National Cancer Institute. Formaldehyde and Cancer Risk [Internet]. National Cancer Institute.; 2011. Available from:
  10. ‌Tobacco [Internet]. Available from:
  11. ‌Borkar NA, Roos B, Prakash YS, Sathish V, Pabelick CM. Nicotinic α7 acetylcholine receptor (α7nAChR) in human airway smooth muscle. Archives of Biochemistry and Biophysics [Internet]. 2021 Jul [cited 2022 Sep 1];706:108897. Available from:
  12. ‌Bacsi A, Pan L, Ba X, Boldogh I. Pathophysiology of Bronchoconstriction: Role of Oxidatively Damaged DNA Repair. Current opinion in allergy and clinical immunology [Internet]. 2016 Feb 1;16(1):59–67. Available from:
  13. ‌Moldoveanu B, Otmishi P, Jani P, Walker J, Sarmiento X, Guardiola J, et al. Inflammatory mechanisms in the lung. Journal of inflammation research [Internet]. 2009;2:1–11. Available from:
  14. ‌Jasper AE, McIver WJ, Sapey E, Walton GM. Understanding the role of neutrophils in chronic inflammatory airway disease. F1000Research. 2019 Apr 26;8:557.
  15. ‌Kim S, Nadel JA. Role of Neutrophils in Mucus Hypersecretion in COPD and Implications for Therapy. Treatments in Respiratory Medicine. 2004;3(3):147–59.
  16. ‌NHS Choices. Quit smoking [Internet]. NHS. 2018. Available from:
  17. ‌Spruit MA, Burtin C, De Boever P, Langer D, Vogiatzis I, Wouters EFM, et al. COPD and exercise: Does it make a difference? Breathe [Internet]. 2016 Jun;12(2):38–49. Available from:
  18. ‌American Cancer Society. Nicotine replacement therapy to help you quit tobacco [Internet]. American Cancer Society; 2012. 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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Yongyi Dai

Master of Science – MSc Translational Neuroscience, Imperial College London, United Kingdom

Daisy (Yongyi) is a student, currently undertaking a master’s degree in Translational Neuroscience. She aims to study and research effective gene therapies to treat neurodegenerative diseases, such as Alzheimer’s disease.

She has completed individual research projects, including “How does age affect our cooperation?” and “Composing a piece of music to aid children with autism.” She led the Sing-Along Surrey project at Royal Holloway University of London between 2020 and 2021 to connect students with residents in local care homes; and she fundraised for charities including Dementia UK and Children’s Hospice South West.

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