Cigarette smoke accounts for more than 80% of chronic obstructive lung disease cases in the U.S. It contains irritants that inflame the air passages, setting off a chain of events that damage cells in the lung, increasing the risk for both COPD and lung cancer.
Different effects of smoking can lead to emphysema or chronic bronchitis, but smokers generally have signs of both conditions.
Smoking is the major cause of emphysema. In some rare inherited disorders, emphysema can develop in nonsmokers.
The key process leading to emphysema is not well understood. It appears that inflammatory cells (T lymphocytes, neutrophils, and alveolar macrophages) release chemicals called enzymes that attack the tissue in the deepest part of the lung where oxygen and carbon dioxide are exchanged. As a result, the bronchioles detach from the alveoli, and holes appear. Airways become narrowed, and breathing out becomes difficult.
The typical COPD patient is a current or former smoker, over age 50, with a pack-a-day habit of more than 20 years. Lung function continues to get worse as the person ages.
On the positive side, smoking rates in the U.S. are dropping, and the proportion of adults under 55 with COPD is gradually declining. This indicates that the high death rate will eventually level out. In particular, the rate of COPD in young African-Americans is declining significantly. The rate in younger Caucasians is not decreasing as dramatically.
Review Date: 04/10/2010
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.