In a finding that could lead to better treatment of smoking-related lung diseases, scientists are reporting that about half of current or former smokers with normal lung function have respiratory symptoms similar to COPD and an increased risk for exacerbations or "flare ups" of their symptoms despite a lack of COPD diagnosis. Many of these individuals show COPD-like symptoms, such as shortness of breath and difficulty exercising. Researchers note they also have a high rate of respiratory medication use despite a lack of data from clinical trials about appropriate treatment of this particular patient population.
In addition to raising the question of whether the definition of COPD should be adjusted, the researchers say that the study highlights a large, understudied patient population who might nevertheless benefit from early treatment intervention. Their study, which appears online and in the current issue of the New England Journal of Medicine, is funded by both the National Heart, Lung, and Blood Institute (NHLBI) and the Foundation for the National Institutes of Health (FNIH).
COPD, or chronic obstructive pulmonary disease, is the third leading cause of death in the United States. It is a progressive lung disease that makes it hard to breathe. Cigarette smoking is the leading cause of COPD. While researchers estimate that millions of Americans have COPD, many have the disease and do not know it. The condition is currently diagnosed using pulmonary function tests that measure how much air you breathe 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 a normal spirometry test (normal lung function). However, the extent and clinical implications of this problem were unknown until now.
For the current study, a research team led by scientists at several institutions, including the University of Utah, conducted an observational study called SPIROMICS (Subpopulations and Intermediate Outcome Measures in COPD Study). It includes patient data collected between 2010 and 2015. The scientists examined respiratory symptoms and measured lung function with spirometry among 2,736 current or former smokers (40 to 80 years of age) as well as controls who had never smoked. They found that respiratory symptoms were present in about half of the current or former smokers despite normal readings on lung function testing. 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.
"This study recognizes a population that was not previously considered to have disease," says Robert Paine, M.D. He and Richard Kanner, M.D., both professors of internal medicine at the University of Utah School of Medicine, were among the co-authors on the study, carried out at several sites across the country. "Further investigation of this group could lead to better treatment of smoking-related lung diseases."
"Right now we say, ‘OK, your spirometry is normal so don't worry about it," says Kanner. "These results show that we should worry about it. We need to broaden our definition of smoking-induced lung disease." Kanner adds that it will be important to conduct additional studies over a period of time to further examine smokers with respiratory symptoms but normal lung function. Do they have early-stage COPD that will progress, or is this a somewhat different condition? In addition, despite the fact that there have been no investigations into appropriate treatments, 43 percent of this group had used bronchodilators, and 23 percent had used glucocorticoids. "Right now all patients with COPD symptoms are treated with a one-size-fits-all approach," says Kanner. "We need to determine the best treatment for each subtype to see if we can do more than we are doing now."
"Clinical Symptoms of Smokers With Preserved Pulmonary Function" was published in the New England Journal of Medicine online on May 11, 2016