MONDAY, June 22, 2015 (HealthDay News) -- Millions of long-term smokers may have undiagnosed lung disease, a new study finds.
Fifty-five percent of those who pass lung function tests still have a respiratory impairment, researchers report.
But, using advanced imaging techniques along with walking and quality-of-life tests can reveal early signs of chronic obstructive pulmonary disease (COPD). An incurable, progressive disease, COPD is associated with smoking and is the third-leading cause of death in the United States, the researchers added.
"Smokers who have 'normal' lung-function tests often have significant respiratory disease. Many of those smokers likely have the early stages of chronic obstructive pulmonary disease," study author Dr. Elizabeth Regan, an assistant professor of medicine at National Jewish Health in Denver, said in a hospital news release.
"We hope these findings will help debunk the myth of the healthy smoker and highlight the importance of smoking prevention and cessation to prevent lung disease and other long-term effects of smoking," Regan added.
The study involved almost 9,000 people between the ages of 45 and 80 who had smoked at least one pack of cigarettes daily for 10 years. Most smoked more than one pack per day, but about half of them were considered disease-free based on their lung-function test results.
To diagnose COPD, patients must blow as hard and as long as they can into a device called a spirometer. This measures how much air they can force out of their lungs and how much they can blow out in just one second depending on their age, size and gender.
When the researchers used additional criteria to assess the participants' lung function, such as CT scans, use of respiratory medication and quality-of-life issues, they found most of those considered "disease-free" had some sort of lung problem.
The study was published June 22 in the journal JAMA Internal Medicine.
Lung scans found emphysema or airway thickening in 42 percent of those thought to be free of lung disease. Meanwhile, 23 percent of the participants had significant shortness of breath compared to almost 4 percent of those who never smoked.
The researchers also found that 15 percent of those in the study took six minutes to walk about 1,000 feet, compared to 4 percent of nonsmokers. Smokers who thought their lungs were fully functioning also had much worse quality of life than those who didn't smoke.
Lung imaging tests can help detect lung cancer, and reduce cancer deaths among former heavy smokers by 20 percent, the researchers said. Diagnosing and treating diseases like COPD early on can also improve people's long-term quality of life, they added.
Visit the U.S. Centers for Disease Control and Prevention for more on the health effects of smoking.