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We all "know" that smoking causes chronic obstructive pulmonary disease (COPD), but the fact is some non-smokers develop the condition, and some smokers do not. What makes the difference?

One of the ongoing mysteries of medical science is the real relationship between smoking and chronic obstructive pulmonary disease, also known as COPD. There are smokers who do not develop COPD. There are non-smokers who do. Understanding what protects smokers or harms non-smokers, with regard to the eventual development of chronic obstructive pulmonary disease, can enable good lifestyle choices.

What Is COPD?

Chronic obstructive pulmonary disease is defined by a triad of symptoms. People who have COPD typically suffer:
  • Chronic bronchitis, which is defined as a productive cough (coughing up phlegm) that lasts two years or more.
  • Emphysema, a permanent enlargement of the alveoli (air sacs) of the lungs, which makes it more difficult for them to capture air.
  • Asthma, a tightening of the passages leading to the alveoli, so less air can get into the lungs.
People who have COPD usually wake up coughing every morning. The cough up clear, colorless sputum. They are prone to bouts with severe respiratory illnesses. Colds and flu produce severe symptoms. They usually don't have trouble catching their breath until the sixth decade of life, after the age of 50, although this is the best known symptom of the disease. 
COPD usually involves both chronic bronchitis and emphysema, but these two components of the overall problem may not be expressed to the same degree. 
People who have more of a problem with chronic bronchitis tend to be obese. People who have more of a problem with emphysema tend to be thin but barrel-chested. People who have more of a problem with chronic bronchitis tend to cough up more phlegm and to suffer swelling. People who have more of a problem with emphysema may cough very little, but they tend to have to breathe through pursed lips and they need to sit up to breathe comfortably.

Differences Between Smokers And Non-Smokers With COPD

Chinese researchers have found that there are significant differences between smokers who develop COPD and non-smokers who develop COPD. Smokers tend to have more emphysema symptoms. Non-smokers tend to have more bronchitis symptoms. Smokers will have difficulty breathing even if they manage to overcome asthma and bronchitis. Non-smokers will be greatly improved just by eliminating the factors that aggravate asthma (cold drafts, dust, irritant chemicals in the air, and allergnes). 
Smokers need to reduce asthma and bronchitis symptoms, but they also need emphysema treatments.
Smokers and non-smokers also respond differently to COPD treatment. By the end stages of COPD, there's not a lot that can be done. Whether or not you have ever smoked, you are likely to need supplemental oxygen. Even with supplemental oxygen, your tissues are likely to be poorly oxygenated. Your lungs just can't get the oxygen into your bloodstream. A condition known as respiratory acidosis may develop, and respiratory failure comes soon thereafter.
Non-smokers who quit smoking early enough in the course of COPD don't get better, but they don't get worse. The loss of the ability of the air sacs to contract and hold air so the bloodstream can absorb oxygen is diminished, but the situation is less likely to become critical. This doesn't answer the question of why a non-smoker should ever develop COPD at all.
Continue reading after recommendations

  • Zhang J, Lin XF, Bai CX. Comparison of clinical features between non-smokers with COPD and smokers with COPD: a retrospective observational study. Int J Chron Obstruct Pulmon Dis. 2014. 9:57-63. doi: 10.2147/COPD.S52416. Epub 2014 Jan 8.
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