Difficulty breathing and a constant cough often are the first signs of chronic obstructive pulmonary disease (COPD), an umbrella term that includes emphysema and chronic bronchitis.
COPD, the third leading cause of death in the United States, kills more than 120,000 Americans each year, and many of the 24 million adults who have the disease or are likely to be diagnosed have never heard of it.
The National Institutes of Health cites three risk factors for the disabling disease.
Smoking. Although the lung damage occurs gradually, most people with tobacco-related emphysema begin to experience symptoms of the disease between the ages of 40 and 60. Current or former smokers account for as many as nine of 10 COPD-related deaths.
Environmental exposure. People who have had long-term exposure to lung irritants such as certain chemicals, dust or fumes in the workplace are at increased risk. Heavy or long-term exposure to secondhand smoke or other air pollutants also may contribute.
Genetic factors. In some people, COPD is caused by a genetic condition known as alpha1-antitrypsin (AAT) deficiency, the lack of a protein necessary for proper lung and liver function. The National Heart Lung and Blood Institute estimates that as many as 100,000 Americans have the deficiency, which can lead to COPD in people who never have smoked or had long-term exposure to harmful pollutants.