More than half of long-term smokers and ex-smokers have lung disease and don’t know it, according to a new study. Research published in the edition of JAMA Internal Medicine found that 55 percent of those who passed a lung-function test had some respiratory impairment.
“The impact of chronic smoking on the lungs and the individual is substantially underestimated when using lung-function tests alone,” senior study author James D. Crapo, MD, a professor of medicine at National Jewish Health, said in a news release. “Lung disease is common in smokers whose lung-function tests fall within population norms,” he added.
Lung-function tests measure how well your lungs work and are used to diagnose chronic obstructive pulmonary disease (COPD), a group of lung diseases that blocks airflow and makes breathing difficult. Emphysema and chronic bronchitis are two of the most common forms of COPD, the third leading cause of death in the United States.
As part of the diagnosis process, patients are asked to blow into a device called a spirometer to measure how much air they can blow out in one second and how much total air they can force out of their lungs. An individual’s results are compared to population norms and adjusted for age, height and gender.
For the study, Crapo and his colleagues evaluated 8,872 people ages 45 to 80 who had smoked at least a pack of cigarettes a day for 10 years. Most smoked more than a pack a day, and nearly half were considered disease-free based on their lung-function test.
The researchers then reevaluated the group that passed the lung-function test. Based on participants’ CT scans, physical abilities, use of respiratory medication and respiratory symptoms, the study team determined that 55 percent actually had respiratory problems. The researchers reported that most were likely to have early-stage COPD.
On the basis of CT scans alone, Crapo and his colleagues saw airway thickening or emphysema in 42 percent of the undiagnosed participants. In addition, 23 percent of the people in the study experienced significant shortness of breath compared to 4 percent of those who had never smoked.
The investigators also found 15 percent of the smokers thought to be disease-free took six minutes to walk 1,000 feet compared to 4 percent of nonsmokers. Smokers who thought their lungs were healthy had a much lower quality of life than those who never smoked.
Recent research has shown that CT screening heavy smokers’ lungs can lead to early detection of lung cancer and reduce deaths by 20 percent. Early detection of COPD using this technology may also bring about early treatment that can control symptoms and ultimately improve quality of life.
The study authors expressed their hope that the study’s findings will encourage long-term smokers to get lung CT screenings to detect early stages of these devastating diseases.