Chronic obstructive pulmonary disease, or COPD, is a chronic inflammatory disease that causes cough with mucus, wheezing, shortness of breath or chest tightness, all of which make breathing  difficult.

Two conditions, emphysema (which involves damage to the air sacs and leads to a lesser gas exchange in the lungs) and chronic bronchitis (which involves inflammation of the lining of the airways, causing thick mucus to build) are common conditions associated with COPD.

Symptoms are most evident when significant lung damage has already occurred, and usually worsen with time. Although COPD has no cure, proper medication and lifestyle changes can reduce some of its symptoms.

It is estimated that 11 million Americans are affected by COPD, the third leading cause of death in the U.S. The disease is more common in people middle-age or older, although it can affect people under 40.

How COPD affects the lungs

The air we breathe enters the lungs through the bronchial tubes or airways. These are connected to smaller tubes (bronchioles) that end in small air sacs (alveoli). Oxygen then passes through the walls of air sacs to enter capillaries and move into the bloodstream. At the same time, carbon dioxide moves from the blood vessels into the air sacs. This process is called gas exchange.

Both airways and air sacs are elastic and fill when we breathe in. When we breathe out, the air sacs deflate. In COPD, damage to the lungs affects elasticity in the airways and air sacs and many of the air sacs’ walls are destroyed. This leads to poor gas exchange.

Less oxygen is being fed into body tissues, and carbon dioxide, a waste gas, is less effectively expelled, resulting in shortness of breath during daily activities, general fatigue, and other symptoms.

COPD symptoms

Some of the common symptoms of COPD include:

  • Shortness of breath, even with basic physical activity;
  • Frequent cough, or cough that produces a lot of mucus;
  • Wheezing;
  • Mucus production (phlegm or sputum);
  • Tightness in the chest.

The symptoms may vary from person to person, and not everyone has all these symptoms. Some people may also experience episodes, called flares, in which the symptoms become worse and persist for several days.

Other possible COPD symptoms include a lack of energy; unintentional weight loss in later stages; swelling in ankles, feet or legs; and cyanosis (lips or fingernails take on a bluish hue).

COPD causes

The causes of COPD are not fully understood. However, long-term exposure to lung irritants damage the lungs and the airways.

For this reason, COPD is strongly associated with tobacco smoking in developed countries, while in developing countries it is often linked to exposure to fumes from cooking oils or heating in poorly ventilated houses, as well as tobacco use.

According to the American Lung Association, between 85-90% of all COPD cases are caused by cigarette smoking.

Other causes include second-hand smoke, such as exposure to tobacco smoke exhaled by others; air pollution; chemical fumes; or dust.

In rare cases, the genetic disorder alpha-1-antitrypsin (AAT) deficiency can cause COPD. AAT is a protein produced in the liver that protects the lungs, but this disorder changes its shape, and the protein cannot leave liver cells to reach the lungs.

Without this protein, white blood cells can damage the lungs (AAT deficiency is a genetic risk factor for emphysema). In rare cases, people with asthma, a chronic lung disease that inflames and narrows the airways, whose disease is not treated properly are at risk of developing COPD.

COPD prevalence in adults

Millions of Americans, and many millions more worldwide, are affected by COPD. Millions of others are thought to have this disease without knowing it because they consider their increasing breathlessness and coughing to be a normal part of aging and don’t recognize such problems as symptoms.

In fact, the COPD Foundation puts the number of diagnosed and non-diagnosed U.S. adults with COPD at around 30 million people.

In most cases, again, the diagnosis is made in middle-age adults who smoke or used to smoke. But those with long-term exposure to harmful fumes in the workplace or home, and to second-hand smoke, may also develop the disease, as could those with genetic risk factors.


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