Understanding COPD in Non-Smokers

Causes and Differences in Symptoms and Outcome

patient talking to doctor about COPD in never smokers
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COPD is more common in people who have smoked, but does occur in nonsmokers, both former smokers and never smokers. Causes may include environmental exposures, occupational exposures, secondhand smoke, childhood infections, and genetic factors. There are a number of differences between COPD in never smokers and people who smoke, ranging from symptoms to diagnostic findings to progression. Of note, is that COPD in never smokers is much more common in women.

Overview and Statistics

Chronic obstructive pulmonary disease (COPD) is a category of lung diseases that involve inflammation and irreversible obstruction in the airways of the lung. Types of COPD include emphysema, chronic bronchitis, and bronchiectasis. Currently the third or fourth leading cause of death in the United States, many people are unaware that they have the disease in the early stages.

Percent of COPD in Non-Smokers

The prevalence of COPD among never smokers varies widely among different regions of the world. In the United States and Europe, studies most often report around 20 percent of people with COPD to be never smokers, and that number may be rising. A 2015 study in Canada found that 30 percent of people with COPD were lifelong non-smokers, translating to an overall prevalence of 4.7 percent. The occurrence of COPD in never smokers varied significantly with gender, with most never smokers with COPD being women.

In other regions of the world, the proportion of never smokers with COPD may be much higher. A 2017 Indian study looking at people with COPD found that 56.5 percent of people with the disease were never smokers. In a 2016 Korean study, that number was 59.6 percent. Again, COPD in never smokers was much more common in women.

Evidence of COPD in Never Smokers on Testing

The above studies looked at people who were diagnosed with COPD. Estimates vary, but in general, a significant amount of lung tissue damage has occurred before any symptoms occur with COPD. This is a good reminder that many never smokers in the United States may have evidence of COPD on pulmonary function tests, even before they have significant symptoms.

Causes

There are a number of risk factors associated with the development of COPD in never smokers. While we often think of "exposures," especially those occurring in adulthood, there is increasing evidence that suggests that factors influencing lung growth in the womb or during early childhood development (such as low birth weight or poor socioeconomic conditions) may increase the risk of COPD in certain individuals. Potential causes include:

Environmental Exposures

Air pollution has been linked with COPD in never smokers, especially in regions such as China. It's important to keep in mind that indoor air pollution can be as serious or more serious than outdoor air pollution. Biomass fuel heating was strongly associated with COPD in never smokers in the Indian study above, and was even noted to be significant in a study in Canada.

While many chemical exposures are found on-the-job, household exposures (such as fumes from gasoline, paints, and stains) may also play a role.

Occupational Exposures

Just as on-the-job exposures are linked with a significant number of lung cancers, these exposures are associated with the development of COPD. A 2017 review of job-related exposures and COPD found that workers who were exposed to vapers, gases, dust, and fumes were 1.22 more likely to develop COPD.

The risk of COPD in never smokers may be much higher in those who have "pneumoconioses," lung diseases related to exposure to substances such as coal and silica.

Secondhand Smoke

Secondhand smoke exposure at any time in life, even in utero (during a mother's pregnancy) is associated with an increased risk.

Asthma

People who have never smoked and have active asthma are 8.3 percent more likely to develop COPD. (The association between asthma and COPD is higher in those who have a history of smoking, with former smokers with active asthma being 20.6 percent more likely to develop COPD, and current smokers, 26.7 percent more likely.)

in the Canadian study above, 36 percent of never smokers with COPD had been diagnosed with asthma.

Lung Infections

Repeated serious childhood respiratory infections are associated with an increased risk of COPD in never smokers. A history of tuberculosis is also linked with COPD, and is a very significant risk factor in areas of the world where tuberculosis is more prevalent.

Genetics

We know that COPD runs in families, and in the past, it was often hard to separate out how much of this risk was due to genetics, and how much was due to common environmental exposures. What we are now learning is that genetics likely plays a considerable role. A 2018 review found that roughly one-fourth of adults have variations in their central airways that occur during development and increase the risk of COPD later in life. One of these variants appeared to raise the risk only in smokers, but another increased risk in both smokers and never smokers.

The genetic condition alpha-1-antitrypsin deficiency is not uncommon and can lead to emphysema (often with onset at an early age) in both smokers and nonsmokers.

Diet

As noted earlier, problems such as poverty as a young child are linked with an increased risk. As far as diet in adults, low consumption of fruits (but not vegetables) had been linked with a greater risk of COPD in women, whether smokers or nonsmokers.

Differences in COPD in Never Smokers

COPD may be somewhat different in never smokers than in people who smoke when it comes to the symptoms of the disease, what may be found on diagnosis, and the progression of the disease.

Differences in Symptoms

On average, never smokers have fewer symptoms of COPD and milder disease than those who smoke or are former smokers. People are less likely to have a chronic cough, and sputum production is often less. Symptoms such as shortness of breath with exercise and wheezing, however, are similar.

Of note, is that COPD may present with symptoms that don't immediately suggest COPD, as COPD isn't always high on the radar screen in never smokers. These symptoms may include weight loss, pain, and even anxiety or depression.

Differences in Diagnosis

COPD in smokers may differ physiologically as well as with findings on imaging tests. Never smokers with the disease have lower levels of inflammatory biomarkers, on average. Never smokers are also less likely to have changes of emphysema on CT.

Differences in Treatment

Most treatments are similar whether someone has smoked or not, but a major goal of treatment in people who smoke is smoking cessation, whereas treatments in nonsmokers focus on medication and exercise.

Differences in Progression

Studies vary with respect to differences in how the disease progresses based on smoking status, with some showing similar rates of exacerbations. Others have found that nonsmokers with COPD have fewer hospitalizations and fewer episodes of pneumonia. Since COPD is an independent risk factor for lung cancer (meaning that the risk is much higher than would be expected based on smoking alone) it's notable that smokers with COPD are more likely to develop the disease. That said, for reasons not explained by smoking, lung cancer in never smokers, especially young women who have never smoked, is increasing.

A Word From Verywell

It's important for people to be aware that COPD can occur in people who have never smoked, and in some regions of the world, it is actually more commonly found in nonsmokers. Just as lung cancer is often misdiagnosed in never smokers, and for that reason found in later stages of the disease, a lack of awareness could contribute to overlooking the diagnosis and greater suffering.

If you have been diagnosed with COPD as a nonsmoker, it's likely you've also experienced the stigma that COPD is a "smoker's disease." This can be terribly frustrating, as instead of supporting you, people may ask you how long you smoked or if you were a closet smoker. While this may be infuriating, it's a good opportunity to educate people about the truth: COPD occurs in smokers and never smokers alike, and both groups deserve the care and support of their friends and family.

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