Millions of Americans with tobacco-related lung disease have symptoms that do not fit any existing tobacco-related disease criteria – including the most common of those, chronic obstructive pulmonary disease (COPD) – according to a new study led by researchers at UC San Francisco.
In a study published Aug. 1, 2023, in the Journal of the American Medical Association (JAMA), the research team found that half of the participants with extensive tobacco exposure had a persistently high level of respiratory symptoms, including shortness of breath, daily cough and phlegm, and decreased ability to exercise, but performed well in the breathing tests used to diagnose COPD.
COPD assessment was an essential part of the “SubPopulations and InteRmediate Outcome Measures in COPD Study” (SPIROMICS) - a multicenter study of 1379 people 40 to 80 years old who had more than 20 pack-years of tobacco exposure (smoking one pack of cigarettes per day for 20 or more years). The study also included control participants who had never smoked cigarettes and did not have airflow obstruction.
Participants were enrolled in SPIROMICS I from November 2010 to July 2015 and followed through July 2021 in an extension study, SPIROMICS II. They underwent spirometry, 6-minute walk distance testing, assessment of respiratory symptoms, and CT scans of their lungs, at yearly visits for 3 to 4 years. Many of these participants then completed another round of testing 5 to 10 years after their original visit.
Some of the study participants were found to have COPD after undergoing spirometry, while others had “preserved spirometry,” meaning they did not have COPD. The researchers found that the vast majority of the participants with tobacco exposure and preserved spirometry (TEPS) and pulmonary symptoms at the beginning of the study continued to have symptoms through more than five years of follow-up. They also had high rates of respiratory exacerbations and shortness of breath that limited their ability to be active over the course of the study.
Additionally, participants with symptomatic TEPS did not have increased incidence of COPD compared those with asymptomatic TEPS (33.0% among participants with symptomatic TEPS vs. 31.6% among those with asymptomatic TEPS), or a faster rate of lung function decline, as measured by the decline in FEV1 over time, compared to asymptomatic TEPS participants. By contrast, participants with COPD did have a more rapid rate of FEV1 decline compared to symptomatic TEPS participants.
In addition to the findings related to symptomatic TEPS, the study also found a higher proportion of black individuals in the study had symptomatic TEPS compared with white participants. They also found an increased risk of progression to COPD in black participants as compared with white participants in this study. The authors suggest an evaluation of the contribution of occupational and environmental exposures, socioeconomic status and structural racism to the development of these symptoms.
