(Reuters Health) - Many current and former smokers who don’t fit the definition of chronic obstructive pulmonary disease (COPD) may still have breathing problems seen in patients diagnosed with the disorder, a U.S. study suggests.
COPD is usually caused by smoking, and symptoms include breathing difficulty, cough, excessive phlegm production and wheezing. Doctors diagnose it by giving patients drugs to open up the airways and then having them blow into a large tube connected to a spirometer, a machine that measures how much air the lungs can hold and how fast patients can exhale.
In the new study, 50 percent of the current and former smokers who performed too well on the spirometry test for a COPD diagnosis still had evidence of airway disease and breathing difficulties that limited their activities.
“These people may have an airway disease that is similar to COPD even though they do not meet the current criteria for COPD,” said lead study author Dr. Prescott Woodruff of the University of California, San Francisco.
Among the current and former smokers who did have symptoms without a formal diagnosis, 42 percent of them took drugs known as bronchodilators to relax the muscles in the lungs and open airways and 23 percent used steroids to ease inflammation that restricts airflow.
“We do not know whether these medications will be beneficial,” Woodruff added by email. “There have been no clinical trials in this population.”
Globally, more than 65 million people have moderate to severe COPD, and the condition causes about 5 percent of all deaths, according to the World Health Organization (WHO).
Most cases are caused by smoking or exposure to second-hand smoke, but working or cooking around certain toxic dusts, chemicals and fuels can also contribute, as can frequent respiratory infections during childhood.
For the study, Woodruff and colleagues reviewed data on respiratory symptoms and COPD test results for 2,736 current or former smokers and a control group of people who had never smoked.
The current or former smokers with COPD symptoms but no diagnosis based on the forced-exhalation test still had the other symptoms at nearly the same rate as people actually diagnosed with mild to moderate COPD, researchers report in the New England Journal of Medicine.
About 65 percent of patients diagnosed with mild to moderate COPD had symptoms. Only 16 percent of people who never smoked did.
Current and former smokers with COPD symptoms but no formal diagnosis also did worse on timed walking tests and lung function assessments than the current and former smokers without symptoms, the study found.
The researchers excluded people with asthma or severe obesity from the analyses, but they cannot say for sure if other underlying medical conditions contribute to some of the symptoms in participants. Because the volunteers were not a random sample, researchers also can’t say that they represent the wider population of current and former smokers. In fact, it’s also possible that participants joined the study because they had symptoms, skewing the results, the study team notes.
Even so, the findings suggest that many people are treated like COPD patients even though they don’t meet the current definition, Dr. Leonardo Fabbri of the University of Modena and Reggio Emilia in Italy noted in an accompanying editorial.
More research is needed to understand these patients because smoking might cause cardiovascular or metabolic diseases that lead to breathing problems even when people don’t have test results that suggest abnormal lung function, Fabbri said by email.
“There are patients with chronic respiratory symptoms even without spirometric abnormalities confirming COPD, suggesting indeed that we should introduce the concept of a clinical chronic pulmonary disease (CPD) induced by smoking in absence of obstruction,” Fabbri said.