Emphysema is a form of chronic (long-term) lung disease. People with emphysema have difficulty breathing from a limitation in blowing air out. There are multiple causes of emphysema, but smoking is by far the most common.
Emphysema results when the delicate linings of the air sacs in the lungs become damaged beyond repair. Most commonly, the toxins in cigarette smoke create the damage. The lung changes of emphysema evolve slowly over years:
As the fragile tissues between air sacs are destroyed, air pockets in the lungs develop.
Air becomes trapped in these spaces of damaged lung tissue.
The lungs slowly enlarge, and breathing requires more effort.
This problem of emphysema is called airflow limitation. During lung function testing, it takes someone with emphysema far longer to empty their lungs than it does a person without emphysema.
Smoking Is a Major Cause of Emphysema
In the vast majority of people, smoking is the cause of emphysema. Exactly how smoking destroys the air sac linings in the lungs isn't known. However, population studies show that smokers are about six times more likely to develop emphysema than nonsmokers.
Estimates vary, but more than 24 million people in the U.S. likely have emphysema or another form of COPD, and probably many of them don't know it. Emphysema and chronic bronchitis are the third-leading cause of death in the U.S.
Interestingly, most heavy smokers do not develop emphysema. Why some smokers get emphysema and others do not is unknown. All heavy smokers experience other negative health effects of smoking, though.