Half of Smokers with Normal Lung Function Have COPD-Like Symptoms
Half of smokers with normal lung function nevertheless have lung damage and symptoms of chronic obstructive lung disease (COPD), according to a study published online in New England Journal of Medicine. The findings suggest that smokers with respiratory symptoms in the absence of a COPD diagnosis may need more treatment than once thought.
COPD is defined as a chronic limitation in airflow in the lungs and is most often caused by smoking. It is the third leading cause of death in the United States and is diagnosed when the flow of air a patient can exhale into a device called a spirometer has dropped to a certain threshold, indicating airway obstruction. The diagnosis does not take into account the frequency or severity of symptoms such as shortness of breath, cough, or reduced exercise tolerance. Many smokers have these symptoms without meeting the definition required for a COPD diagnosis, says R. Graham Barr, MD, DrPH, professor of medicine at Columbia University’s College of Physicians and Surgeons and professor of epidemiology at Columbia’s Mailman School of Public Health.
The study—SPIROMICS (Subpopulations and Intermediate Outcome Measures In COPD Study)—took a closer look at these symptomatic smokers. The investigators collected data between 2010 and 2015 on 2,736 current smokers and former smokers with a smoking history of more than 20 pack-years, from multiple centers in the United States, including NewYork-Presbyterian/Columbia.
About half of the smokers had COPD-like symptoms despite having normal spirometry readings. CT lung scans also revealed that many had thickening of the airways, which occurs in people with chronic bronchitis. Symptomatic smokers had more frequent respiratory illnesses or flare-ups that required the use of respiratory medications or medical attention, including hospitalization, than nonsmokers and nonsymptomatic smokers.
“This study shows that normal airflow does not rule out illness from chronic lung disease, particularly in people with a history of smoking and serious respiratory symptoms,” said Dr. Barr, chair of the study's steering committee and an internist at NewYork-Presbyterian.
“Although this particular study did not look at mortality rates in symptomatic smokers, the findings build on previous studies showing that lung damage detectable on CT scans—from smoking or other causes—may be an important predictor of mortality in addition to airflow limitation.”
Previous research performed by Dr. Barr and Elizabeth Oelsner, MD, MPH, assistant professor of medicine at CUMC and internist at NewYork-Presbyterian/Columbia, underlines the risk of mortality among those with emphysema (or signs of lung tissue destruction) on CT scan. One study found that smokers and nonsmokers without COPD but with signs of emphysema on CT scans had a higher mortality rate than those without lung damage. In a subsequent study, researchers found that respiratory diseases and lung cancer were the most common causes of death in people with lung damage but no airflow obstruction, including those who were not heavy smokers.
The best way to treat symptomatic smokers is still unknown. “Almost all clinical trials have only studied COPD as defined by spirometry. It’s possible the usual COPD medications would work, but we don't know,” said Dr. Barr. The NIH has begun a large clinical trial to address the question. “For now, clinicians may want to pay more attention to symptoms of lung disease in addition to performing spirometry and, when appropriate, lung cancer screening in their patients with a history of cigarette smoking.”
This study was supported by grants (HHSN2682009000019C, HHSN268200900013C, HHSN268200900013C, HHSN268200900014C, HHSN268200900015C, HHSN268200900016C, HHSN268200900017C, HHSN268200900018C, HHSN268200900019C, and HHSN268200900020C) from the National Heart, Lung, and Blood Institute of the National Institutes of Health and by the Foundation for the National Institutes of Health.