COPD Patients Who Have Never Smoked Could Be at Greater Risk of Developing Lung Cancer, Study Suggests

People with chronic obstructive pulmonary disease (COPD) appear to be at greater risk of developing lung cancer even if they have never smoked, according to a study.

COPD is the umbrella term for a group of diseases which prevents air from flowing through a person's airways and cause breathing-related problems, according to the U.S. Centers for Disease Control and Prevention (CDC).

In the early stages, symptoms may include a "nagging cough," shortness of breath, wheezing, and a tight chest. In more advanced cases, a person may have trouble catching their breath or talking and low oxygen levels in the blood may cause their lips and or fingernails may go blue or gray. They may also have problems with mental alertness, a very fast heartbeat, swollen feet and ankles, a lose weight The CDC states 15 million U.S. adults have the condition, with smoking being the leading cause.

To estimate rates of lung cancer in COPD patients who have never smoked, the authors of the paper published in the journal Thorax studied 338,548 people from South Korea from a nationally representative cohort aged between 40 to 84, with no history of lung cancer.

Lung cancer expert Dr.O-Jung Kwon of South Korea's Samsung Medical Center and colleagues followed up with the participants after seven years, on average, and found 1,834 had developed lung cancer. The respondents filled out a questionnaire where they noted whether they had "never" or "ever" smoked.

COPD patients who never smoked were found to have over 2.6 times the incidence of lung cancer compared with those without COPD who did not smoke. The researchers also found the risk of lung cancer in those who had never smoked was similar to those without COPD who smoked at some point in their lives.

According to research cited by the study authors, up to 39 percent of COPD patients have never smoked, and there is little evidence on the link between the condition and lung cancer.

The team acknowledged the study was limited because they did not know how severe COPD was in the participants, and didn't have information on environmental and occupational exposures or the severity of emphysema cases which could have put the participants at greater risk of lung cancer. COPD and lung cancer may have also have been misclassified in the data they used, the authors said.

The team concluded: "COPD was a strong independent risk factor for lung cancer incidence in never smokers. Furthermore, never smokers with COPD had a similar risk of lung cancer compared with ever smokers without COPD.

"Patients with COPD are at a high risk of lung cancer and future studies should evaluate whether COPD patients are candidates for lung cancer screening, irrespective of smoking status."

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A stock image shows a doctor looking at a chest X-ray.