Long-term smokers showed symptoms not fitting any of the existing tobacco-related disease criteria, in a study conducted in the US. The study included participants who had smoked one pack of cigarettes a day for 20 years or more. 1379 people aged 40 to 80 years were recruited.

Half of them showed persistently high levels of respiratory symptoms such as shortness of breath, daily cough and phlegm, and decreased ability to exercise. However, they performed well in the breathing tests used to diagnose chronic obstructive pulmonary disease (COPD), researchers at the University of California-San Francisco (UCSF), US, found.

COPD, known to be associated with long-term tobacco exposure, is evaluated through spirometry. It tests lung function by measuring how quickly and effectively a person fills and empties their lungs at maximum effort.

"We found that many people who have a lot of primary tobacco exposure have the same symptoms as people who have COPD, but can't be diagnosed with COPD," said William McKleroy, first author of the study published in the Journal of the American Medical Association (JAMA). This, he said, was because they performed normally in spirometry.

After this 5-year study, the participants were followed-up for the next 3-4 years, and some for 5 to 10 years after their original visit. The tests included spirometry, 6-minute walk distance testing, assessment of respiratory symptoms, and CT scans of their lungs. Some of the participants were found to have COPD after undergoing spirometry, while others had "preserved spirometry", meaning they did not have COPD.

The pulmonary symptoms of participants with tobacco exposure and preserved spirometry (TEPS) at the start of the study persisted through more than five years of follow-up, the researchers found. They were also found to have high rates of respiratory exacerbations and shortness of breath limiting their ability to be active over the course of the study.

Further, symptomatic TEPS participants did not have increased COPD incidence compared to the asymptomatic TEPS ones. They also did not exhibit a faster rate of lung function decline, measured by the exhaled volume of air forced out in the first second. Participants with COPD, however, did display a faster rate of lung function decline compared to symptomatic TEPS participants.

"These findings suggest that a large proportion of tobacco smoke-exposed persons without airflow obstruction have a persistent, symptomatic non-obstructive chronic airway disease that is distinct from COPD," said Prescott Woodruff, principal investigator of the initial 5-year study. "This (study) demonstrates a major gap in effective and compassionate care for tobacco-exposed persons and highlights the need for further study to find ways to help them," said McKleroy.