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More than 30 million people in the U.S. smoke cigarettes, according to the CDC. Westend61/Getty Images
  • A new study finds that millions of current or former smokers have impaired lung function.
  • These people may not meet the criteria for COPD, but still face serious symptoms.
  • In 2020 more than 30 million American adults smoked cigarettes, according to the Centers for Disease Control and Prevention.

Millions of current and former smokers in the United States who don’t meet the criteria for chronic obstructive pulmonary disease (COPD) may still have impaired lung function, a multi-center study found.

In the study, published August 1 in JAMA, researchers followed people with “tobacco exposure and preserved spirometry” (TEPS) to see how their lung function changed over time.

Spirometry is the most common test used to assess pulmonary function, or how well a person’s lungs are working in terms of lung volumes, airflow rates, and other parameters. Spirometry measures how much air you can breathe, as well as how easily and fast you can exhale.

For people with COPD, spirometry shows an airflow obstruction, indicating a problem with exhaling enough air in the normal amount of time.

In contrast, people with TEPS don’t have the same difficulty exhaling during spirometry. However, some people with TEPS have respiratory symptoms similar to COPD, such as chronic cough, excess phlegm in the lungs, or difficult or labored breathing.

While it’s unknown how many Americans have TEPS with respiratory symptoms, in 2020 more than 30 million American adults smoked cigarettes, according to the Centers for Disease Control and Prevention.

In addition, more than 15 million Americans report that they have been diagnosed with COPD, the CDC said, with many more unaware that they have the condition.

The new study, which is a follow-up on an earlier one, included 1,397 participants from age 40 to 80 years who had smoked cigarettes for more than 20 pack-years. A pack-year is the equivalent of smoking one pack of cigarettes a day for one year.

Of these people, 226 had TEPS with respiratory symptoms, known as symptomatic TEPS. Another 269 had asymptomatic TEPS, or no respiratory symptoms.

The study also included control participants, those with no history of cigarette smoking and no airflow obstruction.

Researchers found that people with symptomatic TEPS showed a similar decline in lung function during follow-up as people with asymptomatic TEPS.

Researchers followed participants for two to 10 years, with an average of 5.8 years.

In addition, around one-third of both groups developed COPD during follow-up, as defined by spirometry. These groups were also much more likely to develop spirometry-defined COPD than people in the control group.

However, people with symptomatic TEPS were more likely to have worsening respiratory symptoms and more difficulty doing daily activities, compared to those with asymptomatic TEPS.

“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,” study author Dr. Prescott Woodruff, chief of UC San Francisco’s Division of Pulmonary, Critical Care, Allergy and Sleep Medicine, said in a statement.

Researchers found that among people with TEPS who completed the final study visit, 48% had “substantial and persistent respiratory symptoms,” even with no evidence of COPD on spirometry.

“Although tobacco-exposed persons with preserved spirometry are currently categorized as having pre-COPD by the COPD guidelines, the data from the current study emphasize that the definition of smoking-related lung disease needs to be broadened so new treatments can be developed,” Woodruff added.

One clinical trial, published last year in The New England Journal of Medicine, found that dual-inhaled bronchodilators did not reduce respiratory symptoms in people with symptomatic TEPS.

Dr.Fady Youssef, MD, a pulmonologist, internist and critical care specialist at MemorialCare Long Beach Medical Center in Long Beach, Calif., emphasized that although some smokers in the study with respiratory symptoms were not diagnosed with COPD, it doesn’t indicate a problem with the test.

“Spirometry identifies one function of the lungs, and it identifies it correctly,” he told Healthline.

“The problem would be if someone hears about this study and thinks that is where the story ends, or that smoking is safe and doesn’t cause lung damage,” he said.

First of all, because of the short follow-up in the study, researchers don’t know which patients might eventually develop COPD, he said.

In addition, “there are other health effects related to smoking that are outside of COPD — in particular, heart disease and lung cancer,” he said.

Smoking is the leading cause of preventable death in the United States, according to the CDC, causing more than 480,000 deaths each year.

One thing Youssef thinks the study did do a nice job with is looking at a patient population that is often excluded from clinical trials of smokers, because those trials tend to focus on COPD.

“So they provided some additional data on those patients,” he said.

The new study had several limitations, including its short follow-up and its reliance on participants reporting their respiratory symptoms. In addition, people with respiratory symptoms may have been more likely to enroll in the initial study, which could lead to bias in the results.

Around half of people with asymptomatic or symptomatic TEPS were women, and the average age of participants was over 60. The majority of participants in both groups were white (57% in the symptomatic group; 82% in the asymptomatic group.)

However, people with symptomatic TEPS were more likely to be female and Black, compared to those with asymptomatic TEPS.

In addition, Black participants with symptomatic or asymptomatic TEPS were more likely to develop spirometry-defined COPD, compared to white participants. A similar racial trend was seen among current smokers versus former smokers.

As a result of these disparities, the researchers called for “an evaluation of the contribution of occupational and environmental exposures, socioeconomic status, and structural racism to the development of these symptoms.”

In another recent study, researchers found that how COPD is assessed may lead to additional disparities.

That study, published April 18 in the Journal of General Internal Medicine, suggests that the use of fixed-ratio spirometry may lead to Black people being under-diagnosed with COPD, even though they have symptoms of this condition.

“African American patients’ COPD is often missed because they are frequently exposed to various kinds of deprivation that seems to result in smaller lungs with comparatively better airflow,” study author Dr. Elizabeth Regan, a physician researcher at National Jewish Health in Colorado, said in a statement.

She and her colleagues called for more effective metrics for assessing COPD risk in Black people, which could improve early detection and treatment.

“Better diagnostic tools will lead to better care for all of our patients, regardless of background,” she said.

A new study finds that current or former smokers may have signs of impaired lung function even if they don’t meet the criteria for known lung diseases like COPD.