Health A-Z

Medical Content Created by the Faculty of the Harvard Medical School


What Is It?

Chronic obstructive pulmonary disease (COPD) refers to a group of disorders that damage the lungs. These disorders make breathing increasingly difficult over time.

The most common forms of COPD are chronic bronchitis and emphysema. Both are chronic illnesses that impair airflow in the lungs. Most cases of COPD are related to cigarette smoking.

Chronic Bronchitis
In this disorder, the air passages in the lungs are inflamed. And the mucus-producing glands in the lung's larger air passages (bronchi) are enlarged. These enlarged glands produce too much mucus. This triggers a cough. In chronic bronchitis, this cough is present for at least three months out of the year for two or more consecutive years.

You are more likely to develop chronic bronchitis if you:

  • Smoke tobacco

  • Are exposed to air pollution

  • Are exposed to airborne organic dusts or toxic gases in the workplace. Cotton mills and plastic manufacturing plants carry particularly high risk.

  • Have a history of frequent respiratory illnesses

  • Live with a smoker

  • Have an identical twin with chronic bronchitis

In this disorder, the tiny air sacs in the lungs (alveoli) are destroyed. The lungs are unable to contract fully. They gradually lose elasticity. Holes develop in the lung tissue. This reduces the lungs' ability to exchange oxygen for carbon dioxide.

Your breathing may become labored and inefficient. You may feel breathless most of the time.

You are more likely to develop emphysema if you:

  • Smoke

  • Are exposed to secondhand smoke

  • Are exposed to airborne irritants or noxious chemicals:

    • Lead

    • Mercury

    • Coal dust

    • Hydrogen sulfide

  • Live in an area with significant air pollution

Some people have an inherited form of emphysema. The lungs lack a protective protein called alpha-1 antitrypsin. In people with alpha-1 antitrypsin deficiency, lung damage can appear as early as age 30.

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From Health A-Z, Harvard Health Publications. Copyright 2007 by the President and Fellows of Harvard College. All rights reserved. Written permission is required to reproduce, in any manner, in whole or in part, the material contained herein. To make a reprint request, contact Harvard Health Publications. Used with permission of StayWell.

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