May 11, 2016
About half of current or former smokers have respiratory symptoms similar to COPD (chronic obstructive pulmonary disease) and an increase of COPD-like symptom flare-ups, despite no COPD diagnosis and tests that show normal lung function.
Those are the findings of a new study appearing in the New England Journal of Medicine titled “Clinical Significance of Smokers with Preserved Pulmonary Function” that was co-authored by David Couper, PhD, clinical professor in the Department of Biostatistics at the University of North Carolina’s Gillings School of Global Public Health. The study was coordinated by the Collaborative Studies Coordinating Center at UNC Chapel Hill.
The researchers also found that many of the current and former smokers in the study showed COPD-like symptoms, such as shortness of breath and difficulty exercising. They also reported a high rate of respiratory medication use despite a lack of data from clinical trials about appropriate treatment of this particular patient population.
The results prompted the researchers to question of whether the definition of COPD should be adjusted to include such individuals presenting with these symptoms. The researchers also stated that the study highlights a large, understudied patient population who might nevertheless benefit from early treatment intervention.
“These symptomatic smokers without COPD have similar outcomes to symptomatic smokers with COPD and tend to have worse outcomes than smokers diagnosed with COPD but who report fewer symptoms of COPD,” said Couper.
COPD, a progressive lung disease that makes it hard to breathe, is the third leading cause of death in the United States. Cigarette smoking is the leading cause of COPD. The condition is currently diagnosed using spirometry, a test that measures how much air an individual breathes out and how fast. Researchers have long observed that some current and former smokers appear to have respiratory symptoms associated with COPD – such as coughing and shortness of breath – despite having normal spirometry tests. However, the extent and clinical implications of this problem were unknown until this study was completed.
The study examined respiratory symptoms and measured lung function with spirometry among 2,736 current or former smokers (40 to 80 years of age) during 2010-2015, as well as controls who had never smoked. Respiratory symptoms were present in about half of the current or former smokers despite normal spirometry readings. Participants who had respiratory symptoms despite normal spirometry had an increased rate of exacerbations or “flare ups” of their symptoms. Using computed tomographic (CT) imaging scans of the lung, the researchers also found a high incidence of thickening of the airways, a sign of lung disease.
Couper said the study opens the door for further inquiry.
“Having identified this particular sub-group of smokers with symptoms but whose lung function does not meet the definition of COPD, the next stage is to characterize them biologically and find an effective way to treat them,” he says.
The study was funded by the National Heart, Lung, and Blood Institute (NHLBI) and the Foundation for the National Institutes of Health (FNIH).