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Why is cigarette smoking strongly linked to chronic bronchitis and COPD?

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Medical illustration of the human chest showing the lungs, diaphragm, ribs, trachea, bronchus, and bronchioles, with one lung cut away to reveal internal structures. — respiratory disease The bronchioles of the lungs are the site where oxygen is exchanged for carbon dioxide during the process of respiration. Inflammation, infection, or obstruction of the bronchioles is often associated with acute or chronic respiratory disease, including bronchiectasis, pneumonia, and lung abscesses.

Cigarette smoking is a primary cause of chronic bronchitis and chronic obstructive pulmonary disease (COPD) because tobacco smoke acts as a noxious trigger that damages the respiratory system.12

In chronic bronchitis, smoking causes an increase in the size and number of mucous glands in the large airways, leading to the characteristic chronic cough and excessive sputum production. Simultaneously, smoking induces inflammation and damage in the smaller bronchioles, which can eventually lead to their obliteration. These changes disrupt the lung's ability to distribute air and oxygen effectively, causing a decline in ventilatory function.1

COPD, which encompasses both chronic bronchitis and emphysema, is strongly linked to smoking, with over 80 percent of diagnosed patients being smokers. The smoke causes progressive destruction of lung tissue and persistent airway obstruction. While the exact susceptibility varies between individuals, the only intervention proven to alter the progression of these conditions is the cessation of smoking.321